The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_lockf.c

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    1 /*-
    2  * Copyright (c) 2008 Isilon Inc http://www.isilon.com/
    3  * Authors: Doug Rabson <dfr@rabson.org>
    4  * Developed with Red Inc: Alfred Perlstein <alfred@freebsd.org>
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   25  * SUCH DAMAGE.
   26  */
   27 /*-
   28  * Copyright (c) 1982, 1986, 1989, 1993
   29  *      The Regents of the University of California.  All rights reserved.
   30  *
   31  * This code is derived from software contributed to Berkeley by
   32  * Scooter Morris at Genentech Inc.
   33  *
   34  * Redistribution and use in source and binary forms, with or without
   35  * modification, are permitted provided that the following conditions
   36  * are met:
   37  * 1. Redistributions of source code must retain the above copyright
   38  *    notice, this list of conditions and the following disclaimer.
   39  * 2. Redistributions in binary form must reproduce the above copyright
   40  *    notice, this list of conditions and the following disclaimer in the
   41  *    documentation and/or other materials provided with the distribution.
   42  * 4. Neither the name of the University nor the names of its contributors
   43  *    may be used to endorse or promote products derived from this software
   44  *    without specific prior written permission.
   45  *
   46  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   47  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   49  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   50  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   51  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   52  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   53  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   54  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   55  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   56  * SUCH DAMAGE.
   57  *
   58  *      @(#)ufs_lockf.c 8.3 (Berkeley) 1/6/94
   59  */
   60 
   61 #include <sys/cdefs.h>
   62 __FBSDID("$FreeBSD: releng/7.3/sys/kern/kern_lockf.c 195485 2009-07-09 09:12:16Z kib $");
   63 
   64 #include "opt_debug_lockf.h"
   65 
   66 #include <sys/param.h>
   67 #include <sys/systm.h>
   68 #include <sys/hash.h>
   69 #include <sys/kernel.h>
   70 #include <sys/limits.h>
   71 #include <sys/lock.h>
   72 #include <sys/mount.h>
   73 #include <sys/mutex.h>
   74 #include <sys/proc.h>
   75 #include <sys/sx.h>
   76 #include <sys/unistd.h>
   77 #include <sys/vnode.h>
   78 #include <sys/malloc.h>
   79 #include <sys/fcntl.h>
   80 #include <sys/lockf.h>
   81 #include <sys/taskqueue.h>
   82 
   83 #ifdef LOCKF_DEBUG
   84 #include <sys/sysctl.h>
   85 
   86 #include <ufs/ufs/quota.h>
   87 #include <ufs/ufs/inode.h>
   88 
   89 static int      lockf_debug = 0; /* control debug output */
   90 SYSCTL_INT(_debug, OID_AUTO, lockf_debug, CTLFLAG_RW, &lockf_debug, 0, "");
   91 #endif
   92 
   93 MALLOC_DEFINE(M_LOCKF, "lockf", "Byte-range locking structures");
   94 
   95 struct owner_edge;
   96 struct owner_vertex;
   97 struct owner_vertex_list;
   98 struct owner_graph;
   99 
  100 #define NOLOCKF (struct lockf_entry *)0
  101 #define SELF    0x1
  102 #define OTHERS  0x2
  103 static void      lf_init(void *);
  104 static int       lf_hash_owner(caddr_t, struct flock *, int);
  105 static int       lf_owner_matches(struct lock_owner *, caddr_t, struct flock *,
  106     int);
  107 static struct lockf_entry *
  108                  lf_alloc_lock(struct lock_owner *);
  109 static int       lf_free_lock(struct lockf_entry *);
  110 static int       lf_clearlock(struct lockf *, struct lockf_entry *);
  111 static int       lf_overlaps(struct lockf_entry *, struct lockf_entry *);
  112 static int       lf_blocks(struct lockf_entry *, struct lockf_entry *);
  113 static void      lf_free_edge(struct lockf_edge *);
  114 static struct lockf_edge *
  115                  lf_alloc_edge(void);
  116 static void      lf_alloc_vertex(struct lockf_entry *);
  117 static int       lf_add_edge(struct lockf_entry *, struct lockf_entry *);
  118 static void      lf_remove_edge(struct lockf_edge *);
  119 static void      lf_remove_outgoing(struct lockf_entry *);
  120 static void      lf_remove_incoming(struct lockf_entry *);
  121 static int       lf_add_outgoing(struct lockf *, struct lockf_entry *);
  122 static int       lf_add_incoming(struct lockf *, struct lockf_entry *);
  123 static int       lf_findoverlap(struct lockf_entry **, struct lockf_entry *,
  124     int);
  125 static struct lockf_entry *
  126                  lf_getblock(struct lockf *, struct lockf_entry *);
  127 static int       lf_getlock(struct lockf *, struct lockf_entry *, struct flock *);
  128 static void      lf_insert_lock(struct lockf *, struct lockf_entry *);
  129 static void      lf_wakeup_lock(struct lockf *, struct lockf_entry *);
  130 static void      lf_update_dependancies(struct lockf *, struct lockf_entry *,
  131     int all, struct lockf_entry_list *);
  132 static void      lf_set_start(struct lockf *, struct lockf_entry *, off_t,
  133         struct lockf_entry_list*);
  134 static void      lf_set_end(struct lockf *, struct lockf_entry *, off_t,
  135         struct lockf_entry_list*);
  136 static int       lf_setlock(struct lockf *, struct lockf_entry *,
  137     struct vnode *, void **cookiep);
  138 static int       lf_cancel(struct lockf *, struct lockf_entry *, void *);
  139 static void      lf_split(struct lockf *, struct lockf_entry *,
  140     struct lockf_entry *, struct lockf_entry_list *);
  141 #ifdef LOCKF_DEBUG
  142 static int       graph_reaches(struct owner_vertex *x, struct owner_vertex *y,
  143     struct owner_vertex_list *path);
  144 static void      graph_check(struct owner_graph *g, int checkorder);
  145 static void      graph_print_vertices(struct owner_vertex_list *set);
  146 #endif
  147 static int       graph_delta_forward(struct owner_graph *g,
  148     struct owner_vertex *x, struct owner_vertex *y,
  149     struct owner_vertex_list *delta);
  150 static int       graph_delta_backward(struct owner_graph *g,
  151     struct owner_vertex *x, struct owner_vertex *y,
  152     struct owner_vertex_list *delta);
  153 static int       graph_add_indices(int *indices, int n,
  154     struct owner_vertex_list *set);
  155 static int       graph_assign_indices(struct owner_graph *g, int *indices,
  156     int nextunused, struct owner_vertex_list *set);
  157 static int       graph_add_edge(struct owner_graph *g,
  158     struct owner_vertex *x, struct owner_vertex *y);
  159 static void      graph_remove_edge(struct owner_graph *g,
  160     struct owner_vertex *x, struct owner_vertex *y);
  161 static struct owner_vertex *graph_alloc_vertex(struct owner_graph *g,
  162     struct lock_owner *lo);
  163 static void      graph_free_vertex(struct owner_graph *g,
  164     struct owner_vertex *v);
  165 static struct owner_graph * graph_init(struct owner_graph *g);
  166 #ifdef LOCKF_DEBUG
  167 static void      lf_print(char *, struct lockf_entry *);
  168 static void      lf_printlist(char *, struct lockf_entry *);
  169 static void      lf_print_owner(struct lock_owner *);
  170 #endif
  171 
  172 /*
  173  * This structure is used to keep track of both local and remote lock
  174  * owners. The lf_owner field of the struct lockf_entry points back at
  175  * the lock owner structure. Each possible lock owner (local proc for
  176  * POSIX fcntl locks, local file for BSD flock locks or <pid,sysid>
  177  * pair for remote locks) is represented by a unique instance of
  178  * struct lock_owner.
  179  *
  180  * If a lock owner has a lock that blocks some other lock or a lock
  181  * that is waiting for some other lock, it also has a vertex in the
  182  * owner_graph below.
  183  *
  184  * Locks:
  185  * (s)          locked by state->ls_lock
  186  * (S)          locked by lf_lock_states_lock
  187  * (l)          locked by lf_lock_owners_lock
  188  * (g)          locked by lf_owner_graph_lock
  189  * (c)          const until freeing
  190  */
  191 #define LOCK_OWNER_HASH_SIZE    256
  192 
  193 struct lock_owner {
  194         LIST_ENTRY(lock_owner) lo_link; /* (l) hash chain */
  195         int     lo_refs;            /* (l) Number of locks referring to this */
  196         int     lo_flags;           /* (c) Flags passwd to lf_advlock */
  197         caddr_t lo_id;              /* (c) Id value passed to lf_advlock */
  198         pid_t   lo_pid;             /* (c) Process Id of the lock owner */
  199         int     lo_sysid;           /* (c) System Id of the lock owner */
  200         struct owner_vertex *lo_vertex; /* (g) entry in deadlock graph */
  201 };
  202 
  203 LIST_HEAD(lock_owner_list, lock_owner);
  204 
  205 static struct sx                lf_lock_states_lock;
  206 static struct lockf_list        lf_lock_states; /* (S) */
  207 static struct sx                lf_lock_owners_lock;
  208 static struct lock_owner_list   lf_lock_owners[LOCK_OWNER_HASH_SIZE]; /* (l) */
  209 
  210 /*
  211  * Structures for deadlock detection.
  212  *
  213  * We have two types of directed graph, the first is the set of locks,
  214  * both active and pending on a vnode. Within this graph, active locks
  215  * are terminal nodes in the graph (i.e. have no out-going
  216  * edges). Pending locks have out-going edges to each blocking active
  217  * lock that prevents the lock from being granted and also to each
  218  * older pending lock that would block them if it was active. The
  219  * graph for each vnode is naturally acyclic; new edges are only ever
  220  * added to or from new nodes (either new pending locks which only add
  221  * out-going edges or new active locks which only add in-coming edges)
  222  * therefore they cannot create loops in the lock graph.
  223  *
  224  * The second graph is a global graph of lock owners. Each lock owner
  225  * is a vertex in that graph and an edge is added to the graph
  226  * whenever an edge is added to a vnode graph, with end points
  227  * corresponding to owner of the new pending lock and the owner of the
  228  * lock upon which it waits. In order to prevent deadlock, we only add
  229  * an edge to this graph if the new edge would not create a cycle.
  230  * 
  231  * The lock owner graph is topologically sorted, i.e. if a node has
  232  * any outgoing edges, then it has an order strictly less than any
  233  * node to which it has an outgoing edge. We preserve this ordering
  234  * (and detect cycles) on edge insertion using Algorithm PK from the
  235  * paper "A Dynamic Topological Sort Algorithm for Directed Acyclic
  236  * Graphs" (ACM Journal of Experimental Algorithms, Vol 11, Article
  237  * No. 1.7)
  238  */
  239 struct owner_vertex;
  240 
  241 struct owner_edge {
  242         LIST_ENTRY(owner_edge) e_outlink; /* (g) link from's out-edge list */
  243         LIST_ENTRY(owner_edge) e_inlink;  /* (g) link to's in-edge list */
  244         int             e_refs;           /* (g) number of times added */
  245         struct owner_vertex *e_from;      /* (c) out-going from here */
  246         struct owner_vertex *e_to;        /* (c) in-coming to here */
  247 };
  248 LIST_HEAD(owner_edge_list, owner_edge);
  249 
  250 struct owner_vertex {
  251         TAILQ_ENTRY(owner_vertex) v_link; /* (g) workspace for edge insertion */
  252         uint32_t        v_gen;            /* (g) workspace for edge insertion */
  253         int             v_order;          /* (g) order of vertex in graph */
  254         struct owner_edge_list v_outedges;/* (g) list of out-edges */
  255         struct owner_edge_list v_inedges; /* (g) list of in-edges */
  256         struct lock_owner *v_owner;       /* (c) corresponding lock owner */
  257 };
  258 TAILQ_HEAD(owner_vertex_list, owner_vertex);
  259 
  260 struct owner_graph {
  261         struct owner_vertex** g_vertices; /* (g) pointers to vertices */
  262         int             g_size;           /* (g) number of vertices */
  263         int             g_space;          /* (g) space allocated for vertices */
  264         int             *g_indexbuf;      /* (g) workspace for loop detection */
  265         uint32_t        g_gen;            /* (g) increment when re-ordering */
  266 };
  267 
  268 static struct sx                lf_owner_graph_lock;
  269 static struct owner_graph       lf_owner_graph;
  270 
  271 /*
  272  * Initialise various structures and locks.
  273  */
  274 static void
  275 lf_init(void *dummy)
  276 {
  277         int i;
  278 
  279         sx_init(&lf_lock_states_lock, "lock states lock");
  280         LIST_INIT(&lf_lock_states);
  281 
  282         sx_init(&lf_lock_owners_lock, "lock owners lock");
  283         for (i = 0; i < LOCK_OWNER_HASH_SIZE; i++)
  284                 LIST_INIT(&lf_lock_owners[i]);
  285 
  286         sx_init(&lf_owner_graph_lock, "owner graph lock");
  287         graph_init(&lf_owner_graph);
  288 }
  289 SYSINIT(lf_init, SI_SUB_LOCK, SI_ORDER_FIRST, lf_init, NULL);
  290 
  291 /*
  292  * Generate a hash value for a lock owner.
  293  */
  294 static int
  295 lf_hash_owner(caddr_t id, struct flock *fl, int flags)
  296 {
  297         uint32_t h;
  298 
  299         if (flags & F_REMOTE) {
  300                 h = HASHSTEP(0, fl->l_pid);
  301                 h = HASHSTEP(h, fl->l_sysid);
  302         } else if (flags & F_FLOCK) {
  303                 h = ((uintptr_t) id) >> 7;
  304         } else {
  305                 struct proc *p = (struct proc *) id;
  306                 h = HASHSTEP(0, p->p_pid);
  307                 h = HASHSTEP(h, 0);
  308         }
  309 
  310         return (h % LOCK_OWNER_HASH_SIZE);
  311 }
  312 
  313 /*
  314  * Return true if a lock owner matches the details passed to
  315  * lf_advlock.
  316  */
  317 static int
  318 lf_owner_matches(struct lock_owner *lo, caddr_t id, struct flock *fl,
  319     int flags)
  320 {
  321         if (flags & F_REMOTE) {
  322                 return lo->lo_pid == fl->l_pid
  323                         && lo->lo_sysid == fl->l_sysid;
  324         } else {
  325                 return lo->lo_id == id;
  326         }
  327 }
  328 
  329 static struct lockf_entry *
  330 lf_alloc_lock(struct lock_owner *lo)
  331 {
  332         struct lockf_entry *lf;
  333 
  334         lf = malloc(sizeof(struct lockf_entry), M_LOCKF, M_WAITOK|M_ZERO);
  335 
  336 #ifdef LOCKF_DEBUG
  337         if (lockf_debug & 4)
  338                 printf("Allocated lock %p\n", lf);
  339 #endif
  340         if (lo) {
  341                 sx_xlock(&lf_lock_owners_lock);
  342                 lo->lo_refs++;
  343                 sx_xunlock(&lf_lock_owners_lock);
  344                 lf->lf_owner = lo;
  345         }
  346 
  347         return (lf);
  348 }
  349 
  350 static int
  351 lf_free_lock(struct lockf_entry *lock)
  352 {
  353 
  354         KASSERT(lock->lf_refs > 0, ("lockf_entry negative ref count %p", lock));
  355         if (--lock->lf_refs > 0)
  356                 return (0);
  357         /*
  358          * Adjust the lock_owner reference count and
  359          * reclaim the entry if this is the last lock
  360          * for that owner.
  361          */
  362         struct lock_owner *lo = lock->lf_owner;
  363         if (lo) {
  364                 KASSERT(LIST_EMPTY(&lock->lf_outedges),
  365                     ("freeing lock with dependancies"));
  366                 KASSERT(LIST_EMPTY(&lock->lf_inedges),
  367                     ("freeing lock with dependants"));
  368                 sx_xlock(&lf_lock_owners_lock);
  369                 KASSERT(lo->lo_refs > 0, ("lock owner refcount"));
  370                 lo->lo_refs--;
  371                 if (lo->lo_refs == 0) {
  372 #ifdef LOCKF_DEBUG
  373                         if (lockf_debug & 1)
  374                                 printf("lf_free_lock: freeing lock owner %p\n",
  375                                     lo);
  376 #endif
  377                         if (lo->lo_vertex) {
  378                                 sx_xlock(&lf_owner_graph_lock);
  379                                 graph_free_vertex(&lf_owner_graph,
  380                                     lo->lo_vertex);
  381                                 sx_xunlock(&lf_owner_graph_lock);
  382                         }
  383                         LIST_REMOVE(lo, lo_link);
  384                         free(lo, M_LOCKF);
  385 #ifdef LOCKF_DEBUG
  386                         if (lockf_debug & 4)
  387                                 printf("Freed lock owner %p\n", lo);
  388 #endif
  389                 }
  390                 sx_unlock(&lf_lock_owners_lock);
  391         }
  392         if ((lock->lf_flags & F_REMOTE) && lock->lf_vnode) {
  393                 vrele(lock->lf_vnode);
  394                 lock->lf_vnode = NULL;
  395         }
  396 #ifdef LOCKF_DEBUG
  397         if (lockf_debug & 4)
  398                 printf("Freed lock %p\n", lock);
  399 #endif
  400         free(lock, M_LOCKF);
  401         return (1);
  402 }
  403 
  404 /*
  405  * Advisory record locking support
  406  */
  407 int
  408 lf_advlockasync(struct vop_advlockasync_args *ap, struct lockf **statep,
  409     u_quad_t size)
  410 {
  411         struct lockf *state, *freestate = NULL;
  412         struct flock *fl = ap->a_fl;
  413         struct lockf_entry *lock;
  414         struct vnode *vp = ap->a_vp;
  415         caddr_t id = ap->a_id;
  416         int flags = ap->a_flags;
  417         int hash;
  418         struct lock_owner *lo;
  419         off_t start, end, oadd;
  420         int error;
  421 
  422         /*
  423          * Handle the F_UNLKSYS case first - no need to mess about
  424          * creating a lock owner for this one.
  425          */
  426         if (ap->a_op == F_UNLCKSYS) {
  427                 lf_clearremotesys(fl->l_sysid);
  428                 return (0);
  429         }
  430 
  431         /*
  432          * Convert the flock structure into a start and end.
  433          */
  434         switch (fl->l_whence) {
  435 
  436         case SEEK_SET:
  437         case SEEK_CUR:
  438                 /*
  439                  * Caller is responsible for adding any necessary offset
  440                  * when SEEK_CUR is used.
  441                  */
  442                 start = fl->l_start;
  443                 break;
  444 
  445         case SEEK_END:
  446                 if (size > OFF_MAX ||
  447                     (fl->l_start > 0 && size > OFF_MAX - fl->l_start))
  448                         return (EOVERFLOW);
  449                 start = size + fl->l_start;
  450                 break;
  451 
  452         default:
  453                 return (EINVAL);
  454         }
  455         if (start < 0)
  456                 return (EINVAL);
  457         if (fl->l_len < 0) {
  458                 if (start == 0)
  459                         return (EINVAL);
  460                 end = start - 1;
  461                 start += fl->l_len;
  462                 if (start < 0)
  463                         return (EINVAL);
  464         } else if (fl->l_len == 0) {
  465                 end = OFF_MAX;
  466         } else {
  467                 oadd = fl->l_len - 1;
  468                 if (oadd > OFF_MAX - start)
  469                         return (EOVERFLOW);
  470                 end = start + oadd;
  471         }
  472         /*
  473          * Avoid the common case of unlocking when inode has no locks.
  474          */
  475         VI_LOCK(vp);
  476         if ((*statep) == NULL) {
  477                 if (ap->a_op != F_SETLK) {
  478                         fl->l_type = F_UNLCK;
  479                         VI_UNLOCK(vp);
  480                         return (0);
  481                 }
  482         }
  483         VI_UNLOCK(vp);
  484 
  485         /*
  486          * Map our arguments to an existing lock owner or create one
  487          * if this is the first time we have seen this owner.
  488          */
  489         hash = lf_hash_owner(id, fl, flags);
  490         sx_xlock(&lf_lock_owners_lock);
  491         LIST_FOREACH(lo, &lf_lock_owners[hash], lo_link)
  492                 if (lf_owner_matches(lo, id, fl, flags))
  493                         break;
  494         if (!lo) {
  495                 /*
  496                  * We initialise the lock with a reference
  497                  * count which matches the new lockf_entry
  498                  * structure created below.
  499                  */
  500                 lo = malloc(sizeof(struct lock_owner), M_LOCKF,
  501                     M_WAITOK|M_ZERO);
  502 #ifdef LOCKF_DEBUG
  503                 if (lockf_debug & 4)
  504                         printf("Allocated lock owner %p\n", lo);
  505 #endif
  506 
  507                 lo->lo_refs = 1;
  508                 lo->lo_flags = flags;
  509                 lo->lo_id = id;
  510                 if (flags & F_REMOTE) {
  511                         lo->lo_pid = fl->l_pid;
  512                         lo->lo_sysid = fl->l_sysid;
  513                 } else if (flags & F_FLOCK) {
  514                         lo->lo_pid = -1;
  515                         lo->lo_sysid = 0;
  516                 } else {
  517                         struct proc *p = (struct proc *) id;
  518                         lo->lo_pid = p->p_pid;
  519                         lo->lo_sysid = 0;
  520                 }
  521                 lo->lo_vertex = NULL;
  522 
  523 #ifdef LOCKF_DEBUG
  524                 if (lockf_debug & 1) {
  525                         printf("lf_advlockasync: new lock owner %p ", lo);
  526                         lf_print_owner(lo);
  527                         printf("\n");
  528                 }
  529 #endif
  530 
  531                 LIST_INSERT_HEAD(&lf_lock_owners[hash], lo, lo_link);
  532         } else {
  533                 /*
  534                  * We have seen this lock owner before, increase its
  535                  * reference count to account for the new lockf_entry
  536                  * structure we create below.
  537                  */
  538                 lo->lo_refs++;
  539         }
  540         sx_xunlock(&lf_lock_owners_lock);
  541 
  542         /*
  543          * Create the lockf structure. We initialise the lf_owner
  544          * field here instead of in lf_alloc_lock() to avoid paying
  545          * the lf_lock_owners_lock tax twice.
  546          */
  547         lock = lf_alloc_lock(NULL);
  548         lock->lf_refs = 1;
  549         lock->lf_start = start;
  550         lock->lf_end = end;
  551         lock->lf_owner = lo;
  552         lock->lf_vnode = vp;
  553         if (flags & F_REMOTE) {
  554                 /*
  555                  * For remote locks, the caller may release its ref to
  556                  * the vnode at any time - we have to ref it here to
  557                  * prevent it from being recycled unexpectedly.
  558                  */
  559                 vref(vp);
  560         }
  561 
  562         /*
  563          * XXX The problem is that VTOI is ufs specific, so it will
  564          * break LOCKF_DEBUG for all other FS's other than UFS because
  565          * it casts the vnode->data ptr to struct inode *.
  566          */
  567 /*      lock->lf_inode = VTOI(ap->a_vp); */
  568         lock->lf_inode = (struct inode *)0;
  569         lock->lf_type = fl->l_type;
  570         LIST_INIT(&lock->lf_outedges);
  571         LIST_INIT(&lock->lf_inedges);
  572         lock->lf_async_task = ap->a_task;
  573         lock->lf_flags = ap->a_flags;
  574 
  575         /*
  576          * Do the requested operation. First find our state structure
  577          * and create a new one if necessary - the caller's *statep
  578          * variable and the state's ls_threads count is protected by
  579          * the vnode interlock.
  580          */
  581         VI_LOCK(vp);
  582         if (vp->v_iflag & VI_DOOMED) {
  583                 VI_UNLOCK(vp);
  584                 lf_free_lock(lock);
  585                 return (ENOENT);
  586         }
  587 
  588         /*
  589          * Allocate a state structure if necessary.
  590          */
  591         state = *statep;
  592         if (state == NULL) {
  593                 struct lockf *ls;
  594 
  595                 VI_UNLOCK(vp);
  596 
  597                 ls = malloc(sizeof(struct lockf), M_LOCKF, M_WAITOK|M_ZERO);
  598                 sx_init(&ls->ls_lock, "ls_lock");
  599                 LIST_INIT(&ls->ls_active);
  600                 LIST_INIT(&ls->ls_pending);
  601                 ls->ls_threads = 1;
  602 
  603                 sx_xlock(&lf_lock_states_lock);
  604                 LIST_INSERT_HEAD(&lf_lock_states, ls, ls_link);
  605                 sx_xunlock(&lf_lock_states_lock);
  606 
  607                 /*
  608                  * Cope if we lost a race with some other thread while
  609                  * trying to allocate memory.
  610                  */
  611                 VI_LOCK(vp);
  612                 if (vp->v_iflag & VI_DOOMED) {
  613                         VI_UNLOCK(vp);
  614                         sx_xlock(&lf_lock_states_lock);
  615                         LIST_REMOVE(ls, ls_link);
  616                         sx_xunlock(&lf_lock_states_lock);
  617                         sx_destroy(&ls->ls_lock);
  618                         free(ls, M_LOCKF);
  619                         lf_free_lock(lock);
  620                         return (ENOENT);
  621                 }
  622                 if ((*statep) == NULL) {
  623                         state = *statep = ls;
  624                         VI_UNLOCK(vp);
  625                 } else {
  626                         state = *statep;
  627                         state->ls_threads++;
  628                         VI_UNLOCK(vp);
  629 
  630                         sx_xlock(&lf_lock_states_lock);
  631                         LIST_REMOVE(ls, ls_link);
  632                         sx_xunlock(&lf_lock_states_lock);
  633                         sx_destroy(&ls->ls_lock);
  634                         free(ls, M_LOCKF);
  635                 }
  636         } else {
  637                 state->ls_threads++;
  638                 VI_UNLOCK(vp);
  639         }
  640 
  641         sx_xlock(&state->ls_lock);
  642         /*
  643          * Recheck the doomed vnode after state->ls_lock is
  644          * locked. lf_purgelocks() requires that no new threads add
  645          * pending locks when vnode is marked by VI_DOOMED flag.
  646          */
  647         VI_LOCK(vp);
  648         if (vp->v_iflag & VI_DOOMED) {
  649                 state->ls_threads--;
  650                 wakeup(state);
  651                 VI_UNLOCK(vp);
  652                 sx_xunlock(&state->ls_lock);
  653                 lf_free_lock(lock);
  654                 return (ENOENT);
  655         }
  656         VI_UNLOCK(vp);
  657 
  658         switch (ap->a_op) {
  659         case F_SETLK:
  660                 error = lf_setlock(state, lock, vp, ap->a_cookiep);
  661                 break;
  662 
  663         case F_UNLCK:
  664                 error = lf_clearlock(state, lock);
  665                 lf_free_lock(lock);
  666                 break;
  667 
  668         case F_GETLK:
  669                 error = lf_getlock(state, lock, fl);
  670                 lf_free_lock(lock);
  671                 break;
  672 
  673         case F_CANCEL:
  674                 if (ap->a_cookiep)
  675                         error = lf_cancel(state, lock, *ap->a_cookiep);
  676                 else
  677                         error = EINVAL;
  678                 lf_free_lock(lock);
  679                 break;
  680 
  681         default:
  682                 lf_free_lock(lock);
  683                 error = EINVAL;
  684                 break;
  685         }
  686 
  687 #ifdef INVARIANTS
  688         /*
  689          * Check for some can't happen stuff. In this case, the active
  690          * lock list becoming disordered or containing mutually
  691          * blocking locks. We also check the pending list for locks
  692          * which should be active (i.e. have no out-going edges).
  693          */
  694         LIST_FOREACH(lock, &state->ls_active, lf_link) {
  695                 struct lockf_entry *lf;
  696                 if (LIST_NEXT(lock, lf_link))
  697                         KASSERT((lock->lf_start
  698                                 <= LIST_NEXT(lock, lf_link)->lf_start),
  699                             ("locks disordered"));
  700                 LIST_FOREACH(lf, &state->ls_active, lf_link) {
  701                         if (lock == lf)
  702                                 break;
  703                         KASSERT(!lf_blocks(lock, lf),
  704                             ("two conflicting active locks"));
  705                         if (lock->lf_owner == lf->lf_owner)
  706                                 KASSERT(!lf_overlaps(lock, lf),
  707                                     ("two overlapping locks from same owner"));
  708                 }
  709         }
  710         LIST_FOREACH(lock, &state->ls_pending, lf_link) {
  711                 KASSERT(!LIST_EMPTY(&lock->lf_outedges),
  712                     ("pending lock which should be active"));
  713         }
  714 #endif
  715         sx_xunlock(&state->ls_lock);
  716 
  717         /*
  718          * If we have removed the last active lock on the vnode and
  719          * this is the last thread that was in-progress, we can free
  720          * the state structure. We update the caller's pointer inside
  721          * the vnode interlock but call free outside.
  722          *
  723          * XXX alternatively, keep the state structure around until
  724          * the filesystem recycles - requires a callback from the
  725          * filesystem.
  726          */
  727         VI_LOCK(vp);
  728 
  729         state->ls_threads--;
  730         wakeup(state);
  731         if (LIST_EMPTY(&state->ls_active) && state->ls_threads == 0) {
  732                 KASSERT(LIST_EMPTY(&state->ls_pending),
  733                     ("freeing state with pending locks"));
  734                 freestate = state;
  735                 *statep = NULL;
  736         }
  737 
  738         VI_UNLOCK(vp);
  739 
  740         if (freestate) {
  741                 sx_xlock(&lf_lock_states_lock);
  742                 LIST_REMOVE(freestate, ls_link);
  743                 sx_xunlock(&lf_lock_states_lock);
  744                 sx_destroy(&freestate->ls_lock);
  745                 free(freestate, M_LOCKF);
  746         }
  747         return (error);
  748 }
  749 
  750 int
  751 lf_advlock(struct vop_advlock_args *ap, struct lockf **statep, u_quad_t size)
  752 {
  753         struct vop_advlockasync_args a;
  754 
  755         a.a_vp = ap->a_vp;
  756         a.a_id = ap->a_id;
  757         a.a_op = ap->a_op;
  758         a.a_fl = ap->a_fl;
  759         a.a_flags = ap->a_flags;
  760         a.a_task = NULL;
  761         a.a_cookiep = NULL;
  762 
  763         return (lf_advlockasync(&a, statep, size));
  764 }
  765 
  766 void
  767 lf_purgelocks(struct vnode *vp, struct lockf **statep)
  768 {
  769         struct lockf *state;
  770         struct lockf_entry *lock, *nlock;
  771 
  772         /*
  773          * For this to work correctly, the caller must ensure that no
  774          * other threads enter the locking system for this vnode,
  775          * e.g. by checking VI_DOOMED. We wake up any threads that are
  776          * sleeping waiting for locks on this vnode and then free all
  777          * the remaining locks.
  778          */
  779         VI_LOCK(vp);
  780         KASSERT(vp->v_iflag & VI_DOOMED,
  781             ("lf_purgelocks: vp %p has not vgone yet", vp));
  782         state = *statep;
  783         if (state) {
  784                 *statep = NULL;
  785                 state->ls_threads++;
  786                 VI_UNLOCK(vp);
  787 
  788                 sx_xlock(&state->ls_lock);
  789                 sx_xlock(&lf_owner_graph_lock);
  790                 LIST_FOREACH_SAFE(lock, &state->ls_pending, lf_link, nlock) {
  791                         LIST_REMOVE(lock, lf_link);
  792                         lf_remove_outgoing(lock);
  793                         lf_remove_incoming(lock);
  794 
  795                         /*
  796                          * If its an async lock, we can just free it
  797                          * here, otherwise we let the sleeping thread
  798                          * free it.
  799                          */
  800                         if (lock->lf_async_task) {
  801                                 lf_free_lock(lock);
  802                         } else {
  803                                 lock->lf_flags |= F_INTR;
  804                                 wakeup(lock);
  805                         }
  806                 }
  807                 sx_xunlock(&lf_owner_graph_lock);
  808                 sx_xunlock(&state->ls_lock);
  809 
  810                 /*
  811                  * Wait for all other threads, sleeping and otherwise
  812                  * to leave.
  813                  */
  814                 VI_LOCK(vp);
  815                 while (state->ls_threads > 1)
  816                         msleep(state, VI_MTX(vp), 0, "purgelocks", 0);
  817                 VI_UNLOCK(vp);
  818 
  819                 /*
  820                  * We can just free all the active locks since they
  821                  * will have no dependancies (we removed them all
  822                  * above). We don't need to bother locking since we
  823                  * are the last thread using this state structure.
  824                  */
  825                 KASSERT(LIST_EMPTY(&state->ls_pending),
  826                     ("lock pending for %p", state));
  827                 LIST_FOREACH_SAFE(lock, &state->ls_active, lf_link, nlock) {
  828                         LIST_REMOVE(lock, lf_link);
  829                         lf_free_lock(lock);
  830                 }
  831                 sx_xlock(&lf_lock_states_lock);
  832                 LIST_REMOVE(state, ls_link);
  833                 sx_xunlock(&lf_lock_states_lock);
  834                 sx_destroy(&state->ls_lock);
  835                 free(state, M_LOCKF);
  836         } else {
  837                 VI_UNLOCK(vp);
  838         }
  839 }
  840 
  841 /*
  842  * Return non-zero if locks 'x' and 'y' overlap.
  843  */
  844 static int
  845 lf_overlaps(struct lockf_entry *x, struct lockf_entry *y)
  846 {
  847 
  848         return (x->lf_start <= y->lf_end && x->lf_end >= y->lf_start);
  849 }
  850 
  851 /*
  852  * Return non-zero if lock 'x' is blocked by lock 'y' (or vice versa).
  853  */
  854 static int
  855 lf_blocks(struct lockf_entry *x, struct lockf_entry *y)
  856 {
  857 
  858         return x->lf_owner != y->lf_owner
  859                 && (x->lf_type == F_WRLCK || y->lf_type == F_WRLCK)
  860                 && lf_overlaps(x, y);
  861 }
  862 
  863 /*
  864  * Allocate a lock edge from the free list
  865  */
  866 static struct lockf_edge *
  867 lf_alloc_edge(void)
  868 {
  869 
  870         return (malloc(sizeof(struct lockf_edge), M_LOCKF, M_WAITOK|M_ZERO));
  871 }
  872 
  873 /*
  874  * Free a lock edge.
  875  */
  876 static void
  877 lf_free_edge(struct lockf_edge *e)
  878 {
  879 
  880         free(e, M_LOCKF);
  881 }
  882 
  883 
  884 /*
  885  * Ensure that the lock's owner has a corresponding vertex in the
  886  * owner graph.
  887  */
  888 static void
  889 lf_alloc_vertex(struct lockf_entry *lock)
  890 {
  891         struct owner_graph *g = &lf_owner_graph;
  892 
  893         if (!lock->lf_owner->lo_vertex)
  894                 lock->lf_owner->lo_vertex =
  895                         graph_alloc_vertex(g, lock->lf_owner);
  896 }
  897 
  898 /*
  899  * Attempt to record an edge from lock x to lock y. Return EDEADLK if
  900  * the new edge would cause a cycle in the owner graph.
  901  */
  902 static int
  903 lf_add_edge(struct lockf_entry *x, struct lockf_entry *y)
  904 {
  905         struct owner_graph *g = &lf_owner_graph;
  906         struct lockf_edge *e;
  907         int error;
  908 
  909 #ifdef INVARIANTS
  910         LIST_FOREACH(e, &x->lf_outedges, le_outlink)
  911                 KASSERT(e->le_to != y, ("adding lock edge twice"));
  912 #endif
  913 
  914         /*
  915          * Make sure the two owners have entries in the owner graph.
  916          */
  917         lf_alloc_vertex(x);
  918         lf_alloc_vertex(y);
  919 
  920         error = graph_add_edge(g, x->lf_owner->lo_vertex,
  921             y->lf_owner->lo_vertex);
  922         if (error)
  923                 return (error);
  924 
  925         e = lf_alloc_edge();
  926         LIST_INSERT_HEAD(&x->lf_outedges, e, le_outlink);
  927         LIST_INSERT_HEAD(&y->lf_inedges, e, le_inlink);
  928         e->le_from = x;
  929         e->le_to = y;
  930 
  931         return (0);
  932 }
  933 
  934 /*
  935  * Remove an edge from the lock graph.
  936  */
  937 static void
  938 lf_remove_edge(struct lockf_edge *e)
  939 {
  940         struct owner_graph *g = &lf_owner_graph;
  941         struct lockf_entry *x = e->le_from;
  942         struct lockf_entry *y = e->le_to;
  943 
  944         graph_remove_edge(g, x->lf_owner->lo_vertex, y->lf_owner->lo_vertex);
  945         LIST_REMOVE(e, le_outlink);
  946         LIST_REMOVE(e, le_inlink);
  947         e->le_from = NULL;
  948         e->le_to = NULL;
  949         lf_free_edge(e);
  950 }
  951 
  952 /*
  953  * Remove all out-going edges from lock x.
  954  */
  955 static void
  956 lf_remove_outgoing(struct lockf_entry *x)
  957 {
  958         struct lockf_edge *e;
  959 
  960         while ((e = LIST_FIRST(&x->lf_outedges)) != NULL) {
  961                 lf_remove_edge(e);
  962         }
  963 }
  964 
  965 /*
  966  * Remove all in-coming edges from lock x.
  967  */
  968 static void
  969 lf_remove_incoming(struct lockf_entry *x)
  970 {
  971         struct lockf_edge *e;
  972 
  973         while ((e = LIST_FIRST(&x->lf_inedges)) != NULL) {
  974                 lf_remove_edge(e);
  975         }
  976 }
  977 
  978 /*
  979  * Walk the list of locks for the file and create an out-going edge
  980  * from lock to each blocking lock.
  981  */
  982 static int
  983 lf_add_outgoing(struct lockf *state, struct lockf_entry *lock)
  984 {
  985         struct lockf_entry *overlap;
  986         int error;
  987 
  988         LIST_FOREACH(overlap, &state->ls_active, lf_link) {
  989                 /*
  990                  * We may assume that the active list is sorted by
  991                  * lf_start.
  992                  */
  993                 if (overlap->lf_start > lock->lf_end)
  994                         break;
  995                 if (!lf_blocks(lock, overlap))
  996                         continue;
  997 
  998                 /*
  999                  * We've found a blocking lock. Add the corresponding
 1000                  * edge to the graphs and see if it would cause a
 1001                  * deadlock.
 1002                  */
 1003                 error = lf_add_edge(lock, overlap);
 1004 
 1005                 /*
 1006                  * The only error that lf_add_edge returns is EDEADLK.
 1007                  * Remove any edges we added and return the error.
 1008                  */
 1009                 if (error) {
 1010                         lf_remove_outgoing(lock);
 1011                         return (error);
 1012                 }
 1013         }
 1014 
 1015         /*
 1016          * We also need to add edges to sleeping locks that block
 1017          * us. This ensures that lf_wakeup_lock cannot grant two
 1018          * mutually blocking locks simultaneously and also enforces a
 1019          * 'first come, first served' fairness model. Note that this
 1020          * only happens if we are blocked by at least one active lock
 1021          * due to the call to lf_getblock in lf_setlock below.
 1022          */
 1023         LIST_FOREACH(overlap, &state->ls_pending, lf_link) {
 1024                 if (!lf_blocks(lock, overlap))
 1025                         continue;
 1026                 /*
 1027                  * We've found a blocking lock. Add the corresponding
 1028                  * edge to the graphs and see if it would cause a
 1029                  * deadlock.
 1030                  */
 1031                 error = lf_add_edge(lock, overlap);
 1032 
 1033                 /*
 1034                  * The only error that lf_add_edge returns is EDEADLK.
 1035                  * Remove any edges we added and return the error.
 1036                  */
 1037                 if (error) {
 1038                         lf_remove_outgoing(lock);
 1039                         return (error);
 1040                 }
 1041         }
 1042 
 1043         return (0);
 1044 }
 1045 
 1046 /*
 1047  * Walk the list of pending locks for the file and create an in-coming
 1048  * edge from lock to each blocking lock.
 1049  */
 1050 static int
 1051 lf_add_incoming(struct lockf *state, struct lockf_entry *lock)
 1052 {
 1053         struct lockf_entry *overlap;
 1054         int error;
 1055 
 1056         LIST_FOREACH(overlap, &state->ls_pending, lf_link) {
 1057                 if (!lf_blocks(lock, overlap))
 1058                         continue;
 1059 
 1060                 /*
 1061                  * We've found a blocking lock. Add the corresponding
 1062                  * edge to the graphs and see if it would cause a
 1063                  * deadlock.
 1064                  */
 1065                 error = lf_add_edge(overlap, lock);
 1066 
 1067                 /*
 1068                  * The only error that lf_add_edge returns is EDEADLK.
 1069                  * Remove any edges we added and return the error.
 1070                  */
 1071                 if (error) {
 1072                         lf_remove_incoming(lock);
 1073                         return (error);
 1074                 }
 1075         }
 1076         return (0);
 1077 }
 1078 
 1079 /*
 1080  * Insert lock into the active list, keeping list entries ordered by
 1081  * increasing values of lf_start.
 1082  */
 1083 static void
 1084 lf_insert_lock(struct lockf *state, struct lockf_entry *lock)
 1085 {
 1086         struct lockf_entry *lf, *lfprev;
 1087 
 1088         if (LIST_EMPTY(&state->ls_active)) {
 1089                 LIST_INSERT_HEAD(&state->ls_active, lock, lf_link);
 1090                 return;
 1091         }
 1092 
 1093         lfprev = NULL;
 1094         LIST_FOREACH(lf, &state->ls_active, lf_link) {
 1095                 if (lf->lf_start > lock->lf_start) {
 1096                         LIST_INSERT_BEFORE(lf, lock, lf_link);
 1097                         return;
 1098                 }
 1099                 lfprev = lf;
 1100         }
 1101         LIST_INSERT_AFTER(lfprev, lock, lf_link);
 1102 }
 1103 
 1104 /*
 1105  * Wake up a sleeping lock and remove it from the pending list now
 1106  * that all its dependancies have been resolved. The caller should
 1107  * arrange for the lock to be added to the active list, adjusting any
 1108  * existing locks for the same owner as needed.
 1109  */
 1110 static void
 1111 lf_wakeup_lock(struct lockf *state, struct lockf_entry *wakelock)
 1112 {
 1113 
 1114         /*
 1115          * Remove from ls_pending list and wake up the caller
 1116          * or start the async notification, as appropriate.
 1117          */
 1118         LIST_REMOVE(wakelock, lf_link);
 1119 #ifdef LOCKF_DEBUG
 1120         if (lockf_debug & 1)
 1121                 lf_print("lf_wakeup_lock: awakening", wakelock);
 1122 #endif /* LOCKF_DEBUG */
 1123         if (wakelock->lf_async_task) {
 1124                 taskqueue_enqueue(taskqueue_thread, wakelock->lf_async_task);
 1125         } else {
 1126                 wakeup(wakelock);
 1127         }
 1128 }
 1129 
 1130 /*
 1131  * Re-check all dependant locks and remove edges to locks that we no
 1132  * longer block. If 'all' is non-zero, the lock has been removed and
 1133  * we must remove all the dependancies, otherwise it has simply been
 1134  * reduced but remains active. Any pending locks which have been been
 1135  * unblocked are added to 'granted'
 1136  */
 1137 static void
 1138 lf_update_dependancies(struct lockf *state, struct lockf_entry *lock, int all,
 1139         struct lockf_entry_list *granted)
 1140 {
 1141         struct lockf_edge *e, *ne;
 1142         struct lockf_entry *deplock;
 1143 
 1144         LIST_FOREACH_SAFE(e, &lock->lf_inedges, le_inlink, ne) {
 1145                 deplock = e->le_from;
 1146                 if (all || !lf_blocks(lock, deplock)) {
 1147                         sx_xlock(&lf_owner_graph_lock);
 1148                         lf_remove_edge(e);
 1149                         sx_xunlock(&lf_owner_graph_lock);
 1150                         if (LIST_EMPTY(&deplock->lf_outedges)) {
 1151                                 lf_wakeup_lock(state, deplock);
 1152                                 LIST_INSERT_HEAD(granted, deplock, lf_link);
 1153                         }
 1154                 }
 1155         }
 1156 }
 1157 
 1158 /*
 1159  * Set the start of an existing active lock, updating dependancies and
 1160  * adding any newly woken locks to 'granted'.
 1161  */
 1162 static void
 1163 lf_set_start(struct lockf *state, struct lockf_entry *lock, off_t new_start,
 1164         struct lockf_entry_list *granted)
 1165 {
 1166 
 1167         KASSERT(new_start >= lock->lf_start, ("can't increase lock"));
 1168         lock->lf_start = new_start;
 1169         LIST_REMOVE(lock, lf_link);
 1170         lf_insert_lock(state, lock);
 1171         lf_update_dependancies(state, lock, FALSE, granted);
 1172 }
 1173 
 1174 /*
 1175  * Set the end of an existing active lock, updating dependancies and
 1176  * adding any newly woken locks to 'granted'.
 1177  */
 1178 static void
 1179 lf_set_end(struct lockf *state, struct lockf_entry *lock, off_t new_end,
 1180         struct lockf_entry_list *granted)
 1181 {
 1182 
 1183         KASSERT(new_end <= lock->lf_end, ("can't increase lock"));
 1184         lock->lf_end = new_end;
 1185         lf_update_dependancies(state, lock, FALSE, granted);
 1186 }
 1187 
 1188 /*
 1189  * Add a lock to the active list, updating or removing any current
 1190  * locks owned by the same owner and processing any pending locks that
 1191  * become unblocked as a result. This code is also used for unlock
 1192  * since the logic for updating existing locks is identical.
 1193  *
 1194  * As a result of processing the new lock, we may unblock existing
 1195  * pending locks as a result of downgrading/unlocking. We simply
 1196  * activate the newly granted locks by looping.
 1197  *
 1198  * Since the new lock already has its dependancies set up, we always
 1199  * add it to the list (unless its an unlock request). This may
 1200  * fragment the lock list in some pathological cases but its probably
 1201  * not a real problem.
 1202  */
 1203 static void
 1204 lf_activate_lock(struct lockf *state, struct lockf_entry *lock)
 1205 {
 1206         struct lockf_entry *overlap, *lf;
 1207         struct lockf_entry_list granted;
 1208         int ovcase;
 1209 
 1210         LIST_INIT(&granted);
 1211         LIST_INSERT_HEAD(&granted, lock, lf_link);
 1212 
 1213         while (!LIST_EMPTY(&granted)) {
 1214                 lock = LIST_FIRST(&granted);
 1215                 LIST_REMOVE(lock, lf_link);
 1216 
 1217                 /*
 1218                  * Skip over locks owned by other processes.  Handle
 1219                  * any locks that overlap and are owned by ourselves.
 1220                  */
 1221                 overlap = LIST_FIRST(&state->ls_active);
 1222                 for (;;) {
 1223                         ovcase = lf_findoverlap(&overlap, lock, SELF);
 1224 
 1225 #ifdef LOCKF_DEBUG
 1226                         if (ovcase && (lockf_debug & 2)) {
 1227                                 printf("lf_setlock: overlap %d", ovcase);
 1228                                 lf_print("", overlap);
 1229                         }
 1230 #endif
 1231                         /*
 1232                          * Six cases:
 1233                          *      0) no overlap
 1234                          *      1) overlap == lock
 1235                          *      2) overlap contains lock
 1236                          *      3) lock contains overlap
 1237                          *      4) overlap starts before lock
 1238                          *      5) overlap ends after lock
 1239                          */
 1240                         switch (ovcase) {
 1241                         case 0: /* no overlap */
 1242                                 break;
 1243 
 1244                         case 1: /* overlap == lock */
 1245                                 /*
 1246                                  * We have already setup the
 1247                                  * dependants for the new lock, taking
 1248                                  * into account a possible downgrade
 1249                                  * or unlock. Remove the old lock.
 1250                                  */
 1251                                 LIST_REMOVE(overlap, lf_link);
 1252                                 lf_update_dependancies(state, overlap, TRUE,
 1253                                         &granted);
 1254                                 lf_free_lock(overlap);
 1255                                 break;
 1256 
 1257                         case 2: /* overlap contains lock */
 1258                                 /*
 1259                                  * Just split the existing lock.
 1260                                  */
 1261                                 lf_split(state, overlap, lock, &granted);
 1262                                 break;
 1263 
 1264                         case 3: /* lock contains overlap */
 1265                                 /*
 1266                                  * Delete the overlap and advance to
 1267                                  * the next entry in the list.
 1268                                  */
 1269                                 lf = LIST_NEXT(overlap, lf_link);
 1270                                 LIST_REMOVE(overlap, lf_link);
 1271                                 lf_update_dependancies(state, overlap, TRUE,
 1272                                         &granted);
 1273                                 lf_free_lock(overlap);
 1274                                 overlap = lf;
 1275                                 continue;
 1276 
 1277                         case 4: /* overlap starts before lock */
 1278                                 /*
 1279                                  * Just update the overlap end and
 1280                                  * move on.
 1281                                  */
 1282                                 lf_set_end(state, overlap, lock->lf_start - 1,
 1283                                     &granted);
 1284                                 overlap = LIST_NEXT(overlap, lf_link);
 1285                                 continue;
 1286 
 1287                         case 5: /* overlap ends after lock */
 1288                                 /*
 1289                                  * Change the start of overlap and
 1290                                  * re-insert.
 1291                                  */
 1292                                 lf_set_start(state, overlap, lock->lf_end + 1,
 1293                                     &granted);
 1294                                 break;
 1295                         }
 1296                         break;
 1297                 }
 1298 #ifdef LOCKF_DEBUG
 1299                 if (lockf_debug & 1) {
 1300                         if (lock->lf_type != F_UNLCK)
 1301                                 lf_print("lf_activate_lock: activated", lock);
 1302                         else
 1303                                 lf_print("lf_activate_lock: unlocked", lock);
 1304                         lf_printlist("lf_activate_lock", lock);
 1305                 }
 1306 #endif /* LOCKF_DEBUG */
 1307                 if (lock->lf_type != F_UNLCK)
 1308                         lf_insert_lock(state, lock);
 1309         }
 1310 }
 1311 
 1312 /*
 1313  * Cancel a pending lock request, either as a result of a signal or a
 1314  * cancel request for an async lock.
 1315  */
 1316 static void
 1317 lf_cancel_lock(struct lockf *state, struct lockf_entry *lock)
 1318 {
 1319         struct lockf_entry_list granted;
 1320 
 1321         /*
 1322          * Note it is theoretically possible that cancelling this lock
 1323          * may allow some other pending lock to become
 1324          * active. Consider this case:
 1325          *
 1326          * Owner        Action          Result          Dependancies
 1327          * 
 1328          * A:           lock [0..0]     succeeds        
 1329          * B:           lock [2..2]     succeeds        
 1330          * C:           lock [1..2]     blocked         C->B
 1331          * D:           lock [0..1]     blocked         C->B,D->A,D->C
 1332          * A:           unlock [0..0]                   C->B,D->C
 1333          * C:           cancel [1..2]   
 1334          */
 1335 
 1336         LIST_REMOVE(lock, lf_link);
 1337 
 1338         /*
 1339          * Removing out-going edges is simple.
 1340          */
 1341         sx_xlock(&lf_owner_graph_lock);
 1342         lf_remove_outgoing(lock);
 1343         sx_xunlock(&lf_owner_graph_lock);
 1344 
 1345         /*
 1346          * Removing in-coming edges may allow some other lock to
 1347          * become active - we use lf_update_dependancies to figure
 1348          * this out.
 1349          */
 1350         LIST_INIT(&granted);
 1351         lf_update_dependancies(state, lock, TRUE, &granted);
 1352         lf_free_lock(lock);
 1353 
 1354         /*
 1355          * Feed any newly active locks to lf_activate_lock.
 1356          */
 1357         while (!LIST_EMPTY(&granted)) {
 1358                 lock = LIST_FIRST(&granted);
 1359                 LIST_REMOVE(lock, lf_link);
 1360                 lf_activate_lock(state, lock);
 1361         }
 1362 }
 1363 
 1364 /*
 1365  * Set a byte-range lock.
 1366  */
 1367 static int
 1368 lf_setlock(struct lockf *state, struct lockf_entry *lock, struct vnode *vp,
 1369     void **cookiep)
 1370 {
 1371         static char lockstr[] = "lockf";
 1372         int priority, error;
 1373 
 1374 #ifdef LOCKF_DEBUG
 1375         if (lockf_debug & 1)
 1376                 lf_print("lf_setlock", lock);
 1377 #endif /* LOCKF_DEBUG */
 1378 
 1379         /*
 1380          * Set the priority
 1381          */
 1382         priority = PLOCK;
 1383         if (lock->lf_type == F_WRLCK)
 1384                 priority += 4;
 1385         if (!(lock->lf_flags & F_NOINTR))
 1386                 priority |= PCATCH;
 1387         /*
 1388          * Scan lock list for this file looking for locks that would block us.
 1389          */
 1390         if (lf_getblock(state, lock)) {
 1391                 /*
 1392                  * Free the structure and return if nonblocking.
 1393                  */
 1394                 if ((lock->lf_flags & F_WAIT) == 0
 1395                     && lock->lf_async_task == NULL) {
 1396                         lf_free_lock(lock);
 1397                         error = EAGAIN;
 1398                         goto out;
 1399                 }
 1400 
 1401                 /*
 1402                  * For flock type locks, we must first remove
 1403                  * any shared locks that we hold before we sleep
 1404                  * waiting for an exclusive lock.
 1405                  */
 1406                 if ((lock->lf_flags & F_FLOCK) &&
 1407                     lock->lf_type == F_WRLCK) {
 1408                         lock->lf_type = F_UNLCK;
 1409                         lf_activate_lock(state, lock);
 1410                         lock->lf_type = F_WRLCK;
 1411                 }
 1412 
 1413                 /*
 1414                  * We are blocked. Create edges to each blocking lock,
 1415                  * checking for deadlock using the owner graph. For
 1416                  * simplicity, we run deadlock detection for all
 1417                  * locks, posix and otherwise.
 1418                  */
 1419                 sx_xlock(&lf_owner_graph_lock);
 1420                 error = lf_add_outgoing(state, lock);
 1421                 sx_xunlock(&lf_owner_graph_lock);
 1422 
 1423                 if (error) {
 1424 #ifdef LOCKF_DEBUG
 1425                         if (lockf_debug & 1)
 1426                                 lf_print("lf_setlock: deadlock", lock);
 1427 #endif
 1428                         lf_free_lock(lock);
 1429                         goto out;
 1430                 }
 1431 
 1432                 /*
 1433                  * We have added edges to everything that blocks
 1434                  * us. Sleep until they all go away.
 1435                  */
 1436                 LIST_INSERT_HEAD(&state->ls_pending, lock, lf_link);
 1437 #ifdef LOCKF_DEBUG
 1438                 if (lockf_debug & 1) {
 1439                         struct lockf_edge *e;
 1440                         LIST_FOREACH(e, &lock->lf_outedges, le_outlink) {
 1441                                 lf_print("lf_setlock: blocking on", e->le_to);
 1442                                 lf_printlist("lf_setlock", e->le_to);
 1443                         }
 1444                 }
 1445 #endif /* LOCKF_DEBUG */
 1446 
 1447                 if ((lock->lf_flags & F_WAIT) == 0) {
 1448                         /*
 1449                          * The caller requested async notification -
 1450                          * this callback happens when the blocking
 1451                          * lock is released, allowing the caller to
 1452                          * make another attempt to take the lock.
 1453                          */
 1454                         *cookiep = (void *) lock;
 1455                         error = EINPROGRESS;
 1456                         goto out;
 1457                 }
 1458 
 1459                 lock->lf_refs++;
 1460                 error = sx_sleep(lock, &state->ls_lock, priority, lockstr, 0);
 1461                 if (lf_free_lock(lock)) {
 1462                         error = EINTR;
 1463                         goto out;
 1464                 }
 1465 
 1466                 /*
 1467                  * We may have been awakened by a signal and/or by a
 1468                  * debugger continuing us (in which cases we must
 1469                  * remove our lock graph edges) and/or by another
 1470                  * process releasing a lock (in which case our edges
 1471                  * have already been removed and we have been moved to
 1472                  * the active list). We may also have been woken by
 1473                  * lf_purgelocks which we report to the caller as
 1474                  * EINTR. In that case, lf_purgelocks will have
 1475                  * removed our lock graph edges.
 1476                  *
 1477                  * Note that it is possible to receive a signal after
 1478                  * we were successfully woken (and moved to the active
 1479                  * list) but before we resumed execution. In this
 1480                  * case, our lf_outedges list will be clear. We
 1481                  * pretend there was no error.
 1482                  *
 1483                  * Note also, if we have been sleeping long enough, we
 1484                  * may now have incoming edges from some newer lock
 1485                  * which is waiting behind us in the queue.
 1486                  */
 1487                 if (lock->lf_flags & F_INTR) {
 1488                         error = EINTR;
 1489                         lf_free_lock(lock);
 1490                         goto out;
 1491                 }
 1492                 if (LIST_EMPTY(&lock->lf_outedges)) {
 1493                         error = 0;
 1494                 } else {
 1495                         lf_cancel_lock(state, lock);
 1496                         goto out;
 1497                 }
 1498 #ifdef LOCKF_DEBUG
 1499                 if (lockf_debug & 1) {
 1500                         lf_print("lf_setlock: granted", lock);
 1501                 }
 1502 #endif
 1503                 goto out;
 1504         }
 1505         /*
 1506          * It looks like we are going to grant the lock. First add
 1507          * edges from any currently pending lock that the new lock
 1508          * would block.
 1509          */
 1510         sx_xlock(&lf_owner_graph_lock);
 1511         error = lf_add_incoming(state, lock);
 1512         sx_xunlock(&lf_owner_graph_lock);
 1513         if (error) {
 1514 #ifdef LOCKF_DEBUG
 1515                 if (lockf_debug & 1)
 1516                         lf_print("lf_setlock: deadlock", lock);
 1517 #endif
 1518                 lf_free_lock(lock);
 1519                 goto out;
 1520         }
 1521 
 1522         /*
 1523          * No blocks!!  Add the lock.  Note that we will
 1524          * downgrade or upgrade any overlapping locks this
 1525          * process already owns.
 1526          */
 1527         lf_activate_lock(state, lock);
 1528         error = 0;
 1529 out:
 1530         return (error);
 1531 }
 1532 
 1533 /*
 1534  * Remove a byte-range lock on an inode.
 1535  *
 1536  * Generally, find the lock (or an overlap to that lock)
 1537  * and remove it (or shrink it), then wakeup anyone we can.
 1538  */
 1539 static int
 1540 lf_clearlock(struct lockf *state, struct lockf_entry *unlock)
 1541 {
 1542         struct lockf_entry *overlap;
 1543 
 1544         overlap = LIST_FIRST(&state->ls_active);
 1545 
 1546         if (overlap == NOLOCKF)
 1547                 return (0);
 1548 #ifdef LOCKF_DEBUG
 1549         if (unlock->lf_type != F_UNLCK)
 1550                 panic("lf_clearlock: bad type");
 1551         if (lockf_debug & 1)
 1552                 lf_print("lf_clearlock", unlock);
 1553 #endif /* LOCKF_DEBUG */
 1554 
 1555         lf_activate_lock(state, unlock);
 1556 
 1557         return (0);
 1558 }
 1559 
 1560 /*
 1561  * Check whether there is a blocking lock, and if so return its
 1562  * details in '*fl'.
 1563  */
 1564 static int
 1565 lf_getlock(struct lockf *state, struct lockf_entry *lock, struct flock *fl)
 1566 {
 1567         struct lockf_entry *block;
 1568 
 1569 #ifdef LOCKF_DEBUG
 1570         if (lockf_debug & 1)
 1571                 lf_print("lf_getlock", lock);
 1572 #endif /* LOCKF_DEBUG */
 1573 
 1574         if ((block = lf_getblock(state, lock))) {
 1575                 fl->l_type = block->lf_type;
 1576                 fl->l_whence = SEEK_SET;
 1577                 fl->l_start = block->lf_start;
 1578                 if (block->lf_end == OFF_MAX)
 1579                         fl->l_len = 0;
 1580                 else
 1581                         fl->l_len = block->lf_end - block->lf_start + 1;
 1582                 fl->l_pid = block->lf_owner->lo_pid;
 1583                 fl->l_sysid = block->lf_owner->lo_sysid;
 1584         } else {
 1585                 fl->l_type = F_UNLCK;
 1586         }
 1587         return (0);
 1588 }
 1589 
 1590 /*
 1591  * Cancel an async lock request.
 1592  */
 1593 static int
 1594 lf_cancel(struct lockf *state, struct lockf_entry *lock, void *cookie)
 1595 {
 1596         struct lockf_entry *reallock;
 1597 
 1598         /*
 1599          * We need to match this request with an existing lock
 1600          * request.
 1601          */
 1602         LIST_FOREACH(reallock, &state->ls_pending, lf_link) {
 1603                 if ((void *) reallock == cookie) {
 1604                         /*
 1605                          * Double-check that this lock looks right
 1606                          * (maybe use a rolling ID for the cancel
 1607                          * cookie instead?)
 1608                          */
 1609                         if (!(reallock->lf_vnode == lock->lf_vnode
 1610                                 && reallock->lf_start == lock->lf_start
 1611                                 && reallock->lf_end == lock->lf_end)) {
 1612                                 return (ENOENT);
 1613                         }
 1614 
 1615                         /*
 1616                          * Make sure this lock was async and then just
 1617                          * remove it from its wait lists.
 1618                          */
 1619                         if (!reallock->lf_async_task) {
 1620                                 return (ENOENT);
 1621                         }
 1622 
 1623                         /*
 1624                          * Note that since any other thread must take
 1625                          * state->ls_lock before it can possibly
 1626                          * trigger the async callback, we are safe
 1627                          * from a race with lf_wakeup_lock, i.e. we
 1628                          * can free the lock (actually our caller does
 1629                          * this).
 1630                          */
 1631                         lf_cancel_lock(state, reallock);
 1632                         return (0);
 1633                 }
 1634         }
 1635 
 1636         /*
 1637          * We didn't find a matching lock - not much we can do here.
 1638          */
 1639         return (ENOENT);
 1640 }
 1641 
 1642 /*
 1643  * Walk the list of locks for an inode and
 1644  * return the first blocking lock.
 1645  */
 1646 static struct lockf_entry *
 1647 lf_getblock(struct lockf *state, struct lockf_entry *lock)
 1648 {
 1649         struct lockf_entry *overlap;
 1650 
 1651         LIST_FOREACH(overlap, &state->ls_active, lf_link) {
 1652                 /*
 1653                  * We may assume that the active list is sorted by
 1654                  * lf_start.
 1655                  */
 1656                 if (overlap->lf_start > lock->lf_end)
 1657                         break;
 1658                 if (!lf_blocks(lock, overlap))
 1659                         continue;
 1660                 return (overlap);
 1661         }
 1662         return (NOLOCKF);
 1663 }
 1664 
 1665 /*
 1666  * Walk the list of locks for an inode to find an overlapping lock (if
 1667  * any) and return a classification of that overlap.
 1668  *
 1669  * Arguments:
 1670  *      *overlap        The place in the lock list to start looking
 1671  *      lock            The lock which is being tested
 1672  *      type            Pass 'SELF' to test only locks with the same
 1673  *                      owner as lock, or 'OTHER' to test only locks
 1674  *                      with a different owner
 1675  *
 1676  * Returns one of six values:
 1677  *      0) no overlap
 1678  *      1) overlap == lock
 1679  *      2) overlap contains lock
 1680  *      3) lock contains overlap
 1681  *      4) overlap starts before lock
 1682  *      5) overlap ends after lock
 1683  *
 1684  * If there is an overlapping lock, '*overlap' is set to point at the
 1685  * overlapping lock.
 1686  *
 1687  * NOTE: this returns only the FIRST overlapping lock.  There
 1688  *       may be more than one.
 1689  */
 1690 static int
 1691 lf_findoverlap(struct lockf_entry **overlap, struct lockf_entry *lock, int type)
 1692 {
 1693         struct lockf_entry *lf;
 1694         off_t start, end;
 1695         int res;
 1696 
 1697         if ((*overlap) == NOLOCKF) {
 1698                 return (0);
 1699         }
 1700 #ifdef LOCKF_DEBUG
 1701         if (lockf_debug & 2)
 1702                 lf_print("lf_findoverlap: looking for overlap in", lock);
 1703 #endif /* LOCKF_DEBUG */
 1704         start = lock->lf_start;
 1705         end = lock->lf_end;
 1706         res = 0;
 1707         while (*overlap) {
 1708                 lf = *overlap;
 1709                 if (lf->lf_start > end)
 1710                         break;
 1711                 if (((type & SELF) && lf->lf_owner != lock->lf_owner) ||
 1712                     ((type & OTHERS) && lf->lf_owner == lock->lf_owner)) {
 1713                         *overlap = LIST_NEXT(lf, lf_link);
 1714                         continue;
 1715                 }
 1716 #ifdef LOCKF_DEBUG
 1717                 if (lockf_debug & 2)
 1718                         lf_print("\tchecking", lf);
 1719 #endif /* LOCKF_DEBUG */
 1720                 /*
 1721                  * OK, check for overlap
 1722                  *
 1723                  * Six cases:
 1724                  *      0) no overlap
 1725                  *      1) overlap == lock
 1726                  *      2) overlap contains lock
 1727                  *      3) lock contains overlap
 1728                  *      4) overlap starts before lock
 1729                  *      5) overlap ends after lock
 1730                  */
 1731                 if (start > lf->lf_end) {
 1732                         /* Case 0 */
 1733 #ifdef LOCKF_DEBUG
 1734                         if (lockf_debug & 2)
 1735                                 printf("no overlap\n");
 1736 #endif /* LOCKF_DEBUG */
 1737                         *overlap = LIST_NEXT(lf, lf_link);
 1738                         continue;
 1739                 }
 1740                 if (lf->lf_start == start && lf->lf_end == end) {
 1741                         /* Case 1 */
 1742 #ifdef LOCKF_DEBUG
 1743                         if (lockf_debug & 2)
 1744                                 printf("overlap == lock\n");
 1745 #endif /* LOCKF_DEBUG */
 1746                         res = 1;
 1747                         break;
 1748                 }
 1749                 if (lf->lf_start <= start && lf->lf_end >= end) {
 1750                         /* Case 2 */
 1751 #ifdef LOCKF_DEBUG
 1752                         if (lockf_debug & 2)
 1753                                 printf("overlap contains lock\n");
 1754 #endif /* LOCKF_DEBUG */
 1755                         res = 2;
 1756                         break;
 1757                 }
 1758                 if (start <= lf->lf_start && end >= lf->lf_end) {
 1759                         /* Case 3 */
 1760 #ifdef LOCKF_DEBUG
 1761                         if (lockf_debug & 2)
 1762                                 printf("lock contains overlap\n");
 1763 #endif /* LOCKF_DEBUG */
 1764                         res = 3;
 1765                         break;
 1766                 }
 1767                 if (lf->lf_start < start && lf->lf_end >= start) {
 1768                         /* Case 4 */
 1769 #ifdef LOCKF_DEBUG
 1770                         if (lockf_debug & 2)
 1771                                 printf("overlap starts before lock\n");
 1772 #endif /* LOCKF_DEBUG */
 1773                         res = 4;
 1774                         break;
 1775                 }
 1776                 if (lf->lf_start > start && lf->lf_end > end) {
 1777                         /* Case 5 */
 1778 #ifdef LOCKF_DEBUG
 1779                         if (lockf_debug & 2)
 1780                                 printf("overlap ends after lock\n");
 1781 #endif /* LOCKF_DEBUG */
 1782                         res = 5;
 1783                         break;
 1784                 }
 1785                 panic("lf_findoverlap: default");
 1786         }
 1787         return (res);
 1788 }
 1789 
 1790 /*
 1791  * Split an the existing 'lock1', based on the extent of the lock
 1792  * described by 'lock2'. The existing lock should cover 'lock2'
 1793  * entirely.
 1794  *
 1795  * Any pending locks which have been been unblocked are added to
 1796  * 'granted'
 1797  */
 1798 static void
 1799 lf_split(struct lockf *state, struct lockf_entry *lock1,
 1800     struct lockf_entry *lock2, struct lockf_entry_list *granted)
 1801 {
 1802         struct lockf_entry *splitlock;
 1803 
 1804 #ifdef LOCKF_DEBUG
 1805         if (lockf_debug & 2) {
 1806                 lf_print("lf_split", lock1);
 1807                 lf_print("splitting from", lock2);
 1808         }
 1809 #endif /* LOCKF_DEBUG */
 1810         /*
 1811          * Check to see if we don't need to split at all.
 1812          */
 1813         if (lock1->lf_start == lock2->lf_start) {
 1814                 lf_set_start(state, lock1, lock2->lf_end + 1, granted);
 1815                 return;
 1816         }
 1817         if (lock1->lf_end == lock2->lf_end) {
 1818                 lf_set_end(state, lock1, lock2->lf_start - 1, granted);
 1819                 return;
 1820         }
 1821         /*
 1822          * Make a new lock consisting of the last part of
 1823          * the encompassing lock.
 1824          */
 1825         splitlock = lf_alloc_lock(lock1->lf_owner);
 1826         memcpy(splitlock, lock1, sizeof *splitlock);
 1827         splitlock->lf_refs = 1;
 1828         if (splitlock->lf_flags & F_REMOTE)
 1829                 vref(splitlock->lf_vnode);
 1830 
 1831         /*
 1832          * This cannot cause a deadlock since any edges we would add
 1833          * to splitlock already exist in lock1. We must be sure to add
 1834          * necessary dependancies to splitlock before we reduce lock1
 1835          * otherwise we may accidentally grant a pending lock that
 1836          * was blocked by the tail end of lock1.
 1837          */
 1838         splitlock->lf_start = lock2->lf_end + 1;
 1839         LIST_INIT(&splitlock->lf_outedges);
 1840         LIST_INIT(&splitlock->lf_inedges);
 1841         sx_xlock(&lf_owner_graph_lock);
 1842         lf_add_incoming(state, splitlock);
 1843         sx_xunlock(&lf_owner_graph_lock);
 1844 
 1845         lf_set_end(state, lock1, lock2->lf_start - 1, granted);
 1846 
 1847         /*
 1848          * OK, now link it in
 1849          */
 1850         lf_insert_lock(state, splitlock);
 1851 }
 1852 
 1853 struct lockdesc {
 1854         STAILQ_ENTRY(lockdesc) link;
 1855         struct vnode *vp;
 1856         struct flock fl;
 1857 };
 1858 STAILQ_HEAD(lockdesclist, lockdesc);
 1859 
 1860 int
 1861 lf_iteratelocks_sysid(int sysid, lf_iterator *fn, void *arg)
 1862 {
 1863         struct lockf *ls;
 1864         struct lockf_entry *lf;
 1865         struct lockdesc *ldesc;
 1866         struct lockdesclist locks;
 1867         int error;
 1868 
 1869         /*
 1870          * In order to keep the locking simple, we iterate over the
 1871          * active lock lists to build a list of locks that need
 1872          * releasing. We then call the iterator for each one in turn.
 1873          *
 1874          * We take an extra reference to the vnode for the duration to
 1875          * make sure it doesn't go away before we are finished.
 1876          */
 1877         STAILQ_INIT(&locks);
 1878         sx_xlock(&lf_lock_states_lock);
 1879         LIST_FOREACH(ls, &lf_lock_states, ls_link) {
 1880                 sx_xlock(&ls->ls_lock);
 1881                 LIST_FOREACH(lf, &ls->ls_active, lf_link) {
 1882                         if (lf->lf_owner->lo_sysid != sysid)
 1883                                 continue;
 1884 
 1885                         ldesc = malloc(sizeof(struct lockdesc), M_LOCKF,
 1886                             M_WAITOK);
 1887                         ldesc->vp = lf->lf_vnode;
 1888                         vref(ldesc->vp);
 1889                         ldesc->fl.l_start = lf->lf_start;
 1890                         if (lf->lf_end == OFF_MAX)
 1891                                 ldesc->fl.l_len = 0;
 1892                         else
 1893                                 ldesc->fl.l_len =
 1894                                         lf->lf_end - lf->lf_start + 1;
 1895                         ldesc->fl.l_whence = SEEK_SET;
 1896                         ldesc->fl.l_type = F_UNLCK;
 1897                         ldesc->fl.l_pid = lf->lf_owner->lo_pid;
 1898                         ldesc->fl.l_sysid = sysid;
 1899                         STAILQ_INSERT_TAIL(&locks, ldesc, link);
 1900                 }
 1901                 sx_xunlock(&ls->ls_lock);
 1902         }
 1903         sx_xunlock(&lf_lock_states_lock);
 1904 
 1905         /*
 1906          * Call the iterator function for each lock in turn. If the
 1907          * iterator returns an error code, just free the rest of the
 1908          * lockdesc structures.
 1909          */
 1910         error = 0;
 1911         while ((ldesc = STAILQ_FIRST(&locks)) != NULL) {
 1912                 STAILQ_REMOVE_HEAD(&locks, link);
 1913                 if (!error)
 1914                         error = fn(ldesc->vp, &ldesc->fl, arg);
 1915                 vrele(ldesc->vp);
 1916                 free(ldesc, M_LOCKF);
 1917         }
 1918 
 1919         return (error);
 1920 }
 1921 
 1922 int
 1923 lf_iteratelocks_vnode(struct vnode *vp, lf_iterator *fn, void *arg)
 1924 {
 1925         struct lockf *ls;
 1926         struct lockf_entry *lf;
 1927         struct lockdesc *ldesc;
 1928         struct lockdesclist locks;
 1929         int error;
 1930 
 1931         /*
 1932          * In order to keep the locking simple, we iterate over the
 1933          * active lock lists to build a list of locks that need
 1934          * releasing. We then call the iterator for each one in turn.
 1935          *
 1936          * We take an extra reference to the vnode for the duration to
 1937          * make sure it doesn't go away before we are finished.
 1938          */
 1939         STAILQ_INIT(&locks);
 1940         VI_LOCK(vp);
 1941         ls = vp->v_lockf;
 1942         if (!ls) {
 1943                 VI_UNLOCK(vp);
 1944                 return (0);
 1945         }
 1946         ls->ls_threads++;
 1947         VI_UNLOCK(vp);
 1948 
 1949         sx_xlock(&ls->ls_lock);
 1950         LIST_FOREACH(lf, &ls->ls_active, lf_link) {
 1951                 ldesc = malloc(sizeof(struct lockdesc), M_LOCKF,
 1952                     M_WAITOK);
 1953                 ldesc->vp = lf->lf_vnode;
 1954                 vref(ldesc->vp);
 1955                 ldesc->fl.l_start = lf->lf_start;
 1956                 if (lf->lf_end == OFF_MAX)
 1957                         ldesc->fl.l_len = 0;
 1958                 else
 1959                         ldesc->fl.l_len =
 1960                                 lf->lf_end - lf->lf_start + 1;
 1961                 ldesc->fl.l_whence = SEEK_SET;
 1962                 ldesc->fl.l_type = F_UNLCK;
 1963                 ldesc->fl.l_pid = lf->lf_owner->lo_pid;
 1964                 ldesc->fl.l_sysid = lf->lf_owner->lo_sysid;
 1965                 STAILQ_INSERT_TAIL(&locks, ldesc, link);
 1966         }
 1967         sx_xunlock(&ls->ls_lock);
 1968         VI_LOCK(vp);
 1969         ls->ls_threads--;
 1970         wakeup(ls);
 1971         VI_UNLOCK(vp);
 1972 
 1973         /*
 1974          * Call the iterator function for each lock in turn. If the
 1975          * iterator returns an error code, just free the rest of the
 1976          * lockdesc structures.
 1977          */
 1978         error = 0;
 1979         while ((ldesc = STAILQ_FIRST(&locks)) != NULL) {
 1980                 STAILQ_REMOVE_HEAD(&locks, link);
 1981                 if (!error)
 1982                         error = fn(ldesc->vp, &ldesc->fl, arg);
 1983                 vrele(ldesc->vp);
 1984                 free(ldesc, M_LOCKF);
 1985         }
 1986 
 1987         return (error);
 1988 }
 1989 
 1990 static int
 1991 lf_clearremotesys_iterator(struct vnode *vp, struct flock *fl, void *arg)
 1992 {
 1993 
 1994         VOP_ADVLOCK(vp, 0, F_UNLCK, fl, F_REMOTE);
 1995         return (0);
 1996 }
 1997 
 1998 void
 1999 lf_clearremotesys(int sysid)
 2000 {
 2001 
 2002         KASSERT(sysid != 0, ("Can't clear local locks with F_UNLCKSYS"));
 2003         lf_iteratelocks_sysid(sysid, lf_clearremotesys_iterator, NULL);
 2004 }
 2005 
 2006 int
 2007 lf_countlocks(int sysid)
 2008 {
 2009         int i;
 2010         struct lock_owner *lo;
 2011         int count;
 2012 
 2013         count = 0;
 2014         sx_xlock(&lf_lock_owners_lock);
 2015         for (i = 0; i < LOCK_OWNER_HASH_SIZE; i++)
 2016                 LIST_FOREACH(lo, &lf_lock_owners[i], lo_link)
 2017                         if (lo->lo_sysid == sysid)
 2018                                 count += lo->lo_refs;
 2019         sx_xunlock(&lf_lock_owners_lock);
 2020 
 2021         return (count);
 2022 }
 2023 
 2024 #ifdef LOCKF_DEBUG
 2025 
 2026 /*
 2027  * Return non-zero if y is reachable from x using a brute force
 2028  * search. If reachable and path is non-null, return the route taken
 2029  * in path.
 2030  */
 2031 static int
 2032 graph_reaches(struct owner_vertex *x, struct owner_vertex *y,
 2033     struct owner_vertex_list *path)
 2034 {
 2035         struct owner_edge *e;
 2036 
 2037         if (x == y) {
 2038                 if (path)
 2039                         TAILQ_INSERT_HEAD(path, x, v_link);
 2040                 return 1;
 2041         }
 2042 
 2043         LIST_FOREACH(e, &x->v_outedges, e_outlink) {
 2044                 if (graph_reaches(e->e_to, y, path)) {
 2045                         if (path)
 2046                                 TAILQ_INSERT_HEAD(path, x, v_link);
 2047                         return 1;
 2048                 }
 2049         }
 2050         return 0;
 2051 }
 2052 
 2053 /*
 2054  * Perform consistency checks on the graph. Make sure the values of
 2055  * v_order are correct. If checkorder is non-zero, check no vertex can
 2056  * reach any other vertex with a smaller order.
 2057  */
 2058 static void
 2059 graph_check(struct owner_graph *g, int checkorder)
 2060 {
 2061         int i, j;
 2062 
 2063         for (i = 0; i < g->g_size; i++) {
 2064                 if (!g->g_vertices[i]->v_owner)
 2065                         continue;
 2066                 KASSERT(g->g_vertices[i]->v_order == i,
 2067                     ("lock graph vertices disordered"));
 2068                 if (checkorder) {
 2069                         for (j = 0; j < i; j++) {
 2070                                 if (!g->g_vertices[j]->v_owner)
 2071                                         continue;
 2072                                 KASSERT(!graph_reaches(g->g_vertices[i],
 2073                                         g->g_vertices[j], NULL),
 2074                                     ("lock graph vertices disordered"));
 2075                         }
 2076                 }
 2077         }
 2078 }
 2079 
 2080 static void
 2081 graph_print_vertices(struct owner_vertex_list *set)
 2082 {
 2083         struct owner_vertex *v;
 2084 
 2085         printf("{ ");
 2086         TAILQ_FOREACH(v, set, v_link) {
 2087                 printf("%d:", v->v_order);
 2088                 lf_print_owner(v->v_owner);
 2089                 if (TAILQ_NEXT(v, v_link))
 2090                         printf(", ");
 2091         }
 2092         printf(" }\n");
 2093 }
 2094 
 2095 #endif
 2096 
 2097 /*
 2098  * Calculate the sub-set of vertices v from the affected region [y..x]
 2099  * where v is reachable from y. Return -1 if a loop was detected
 2100  * (i.e. x is reachable from y, otherwise the number of vertices in
 2101  * this subset.
 2102  */
 2103 static int
 2104 graph_delta_forward(struct owner_graph *g, struct owner_vertex *x,
 2105     struct owner_vertex *y, struct owner_vertex_list *delta)
 2106 {
 2107         uint32_t gen;
 2108         struct owner_vertex *v;
 2109         struct owner_edge *e;
 2110         int n;
 2111 
 2112         /*
 2113          * We start with a set containing just y. Then for each vertex
 2114          * v in the set so far unprocessed, we add each vertex that v
 2115          * has an out-edge to and that is within the affected region
 2116          * [y..x]. If we see the vertex x on our travels, stop
 2117          * immediately.
 2118          */
 2119         TAILQ_INIT(delta);
 2120         TAILQ_INSERT_TAIL(delta, y, v_link);
 2121         v = y;
 2122         n = 1;
 2123         gen = g->g_gen;
 2124         while (v) {
 2125                 LIST_FOREACH(e, &v->v_outedges, e_outlink) {
 2126                         if (e->e_to == x)
 2127                                 return -1;
 2128                         if (e->e_to->v_order < x->v_order
 2129                             && e->e_to->v_gen != gen) {
 2130                                 e->e_to->v_gen = gen;
 2131                                 TAILQ_INSERT_TAIL(delta, e->e_to, v_link);
 2132                                 n++;
 2133                         }
 2134                 }
 2135                 v = TAILQ_NEXT(v, v_link);
 2136         }
 2137 
 2138         return (n);
 2139 }
 2140 
 2141 /*
 2142  * Calculate the sub-set of vertices v from the affected region [y..x]
 2143  * where v reaches x. Return the number of vertices in this subset.
 2144  */
 2145 static int
 2146 graph_delta_backward(struct owner_graph *g, struct owner_vertex *x,
 2147     struct owner_vertex *y, struct owner_vertex_list *delta)
 2148 {
 2149         uint32_t gen;
 2150         struct owner_vertex *v;
 2151         struct owner_edge *e;
 2152         int n;
 2153 
 2154         /*
 2155          * We start with a set containing just x. Then for each vertex
 2156          * v in the set so far unprocessed, we add each vertex that v
 2157          * has an in-edge from and that is within the affected region
 2158          * [y..x].
 2159          */
 2160         TAILQ_INIT(delta);
 2161         TAILQ_INSERT_TAIL(delta, x, v_link);
 2162         v = x;
 2163         n = 1;
 2164         gen = g->g_gen;
 2165         while (v) {
 2166                 LIST_FOREACH(e, &v->v_inedges, e_inlink) {
 2167                         if (e->e_from->v_order > y->v_order
 2168                             && e->e_from->v_gen != gen) {
 2169                                 e->e_from->v_gen = gen;
 2170                                 TAILQ_INSERT_HEAD(delta, e->e_from, v_link);
 2171                                 n++;
 2172                         }
 2173                 }
 2174                 v = TAILQ_PREV(v, owner_vertex_list, v_link);
 2175         }
 2176 
 2177         return (n);
 2178 }
 2179 
 2180 static int
 2181 graph_add_indices(int *indices, int n, struct owner_vertex_list *set)
 2182 {
 2183         struct owner_vertex *v;
 2184         int i, j;
 2185 
 2186         TAILQ_FOREACH(v, set, v_link) {
 2187                 for (i = n;
 2188                      i > 0 && indices[i - 1] > v->v_order; i--)
 2189                         ;
 2190                 for (j = n - 1; j >= i; j--)
 2191                         indices[j + 1] = indices[j];
 2192                 indices[i] = v->v_order;
 2193                 n++;
 2194         }
 2195 
 2196         return (n);
 2197 }
 2198 
 2199 static int
 2200 graph_assign_indices(struct owner_graph *g, int *indices, int nextunused,
 2201     struct owner_vertex_list *set)
 2202 {
 2203         struct owner_vertex *v, *vlowest;
 2204 
 2205         while (!TAILQ_EMPTY(set)) {
 2206                 vlowest = NULL;
 2207                 TAILQ_FOREACH(v, set, v_link) {
 2208                         if (!vlowest || v->v_order < vlowest->v_order)
 2209                                 vlowest = v;
 2210                 }
 2211                 TAILQ_REMOVE(set, vlowest, v_link);
 2212                 vlowest->v_order = indices[nextunused];
 2213                 g->g_vertices[vlowest->v_order] = vlowest;
 2214                 nextunused++;
 2215         }
 2216 
 2217         return (nextunused);
 2218 }
 2219 
 2220 static int
 2221 graph_add_edge(struct owner_graph *g, struct owner_vertex *x,
 2222     struct owner_vertex *y)
 2223 {
 2224         struct owner_edge *e;
 2225         struct owner_vertex_list deltaF, deltaB;
 2226         int nF, nB, n, vi, i;
 2227         int *indices;
 2228 
 2229         sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
 2230 
 2231         LIST_FOREACH(e, &x->v_outedges, e_outlink) {
 2232                 if (e->e_to == y) {
 2233                         e->e_refs++;
 2234                         return (0);
 2235                 }
 2236         }
 2237 
 2238 #ifdef LOCKF_DEBUG
 2239         if (lockf_debug & 8) {
 2240                 printf("adding edge %d:", x->v_order);
 2241                 lf_print_owner(x->v_owner);
 2242                 printf(" -> %d:", y->v_order);
 2243                 lf_print_owner(y->v_owner);
 2244                 printf("\n");
 2245         }
 2246 #endif
 2247         if (y->v_order < x->v_order) {
 2248                 /*
 2249                  * The new edge violates the order. First find the set
 2250                  * of affected vertices reachable from y (deltaF) and
 2251                  * the set of affect vertices affected that reach x
 2252                  * (deltaB), using the graph generation number to
 2253                  * detect whether we have visited a given vertex
 2254                  * already. We re-order the graph so that each vertex
 2255                  * in deltaB appears before each vertex in deltaF.
 2256                  *
 2257                  * If x is a member of deltaF, then the new edge would
 2258                  * create a cycle. Otherwise, we may assume that
 2259                  * deltaF and deltaB are disjoint.
 2260                  */
 2261                 g->g_gen++;
 2262                 if (g->g_gen == 0) {
 2263                         /*
 2264                          * Generation wrap.
 2265                          */
 2266                         for (vi = 0; vi < g->g_size; vi++) {
 2267                                 g->g_vertices[vi]->v_gen = 0;
 2268                         }
 2269                         g->g_gen++;
 2270                 }
 2271                 nF = graph_delta_forward(g, x, y, &deltaF);
 2272                 if (nF < 0) {
 2273 #ifdef LOCKF_DEBUG
 2274                         if (lockf_debug & 8) {
 2275                                 struct owner_vertex_list path;
 2276                                 printf("deadlock: ");
 2277                                 TAILQ_INIT(&path);
 2278                                 graph_reaches(y, x, &path);
 2279                                 graph_print_vertices(&path);
 2280                         }
 2281 #endif
 2282                         return (EDEADLK);
 2283                 }
 2284 
 2285 #ifdef LOCKF_DEBUG
 2286                 if (lockf_debug & 8) {
 2287                         printf("re-ordering graph vertices\n");
 2288                         printf("deltaF = ");
 2289                         graph_print_vertices(&deltaF);
 2290                 }
 2291 #endif
 2292 
 2293                 nB = graph_delta_backward(g, x, y, &deltaB);
 2294 
 2295 #ifdef LOCKF_DEBUG
 2296                 if (lockf_debug & 8) {
 2297                         printf("deltaB = ");
 2298                         graph_print_vertices(&deltaB);
 2299                 }
 2300 #endif
 2301 
 2302                 /*
 2303                  * We first build a set of vertex indices (vertex
 2304                  * order values) that we may use, then we re-assign
 2305                  * orders first to those vertices in deltaB, then to
 2306                  * deltaF. Note that the contents of deltaF and deltaB
 2307                  * may be partially disordered - we perform an
 2308                  * insertion sort while building our index set.
 2309                  */
 2310                 indices = g->g_indexbuf;
 2311                 n = graph_add_indices(indices, 0, &deltaF);
 2312                 graph_add_indices(indices, n, &deltaB);
 2313 
 2314                 /*
 2315                  * We must also be sure to maintain the relative
 2316                  * ordering of deltaF and deltaB when re-assigning
 2317                  * vertices. We do this by iteratively removing the
 2318                  * lowest ordered element from the set and assigning
 2319                  * it the next value from our new ordering.
 2320                  */
 2321                 i = graph_assign_indices(g, indices, 0, &deltaB);
 2322                 graph_assign_indices(g, indices, i, &deltaF);
 2323 
 2324 #ifdef LOCKF_DEBUG
 2325                 if (lockf_debug & 8) {
 2326                         struct owner_vertex_list set;
 2327                         TAILQ_INIT(&set);
 2328                         for (i = 0; i < nB + nF; i++)
 2329                                 TAILQ_INSERT_TAIL(&set,
 2330                                     g->g_vertices[indices[i]], v_link);
 2331                         printf("new ordering = ");
 2332                         graph_print_vertices(&set);
 2333                 }
 2334 #endif
 2335         }
 2336 
 2337         KASSERT(x->v_order < y->v_order, ("Failed to re-order graph"));
 2338 
 2339 #ifdef LOCKF_DEBUG
 2340         if (lockf_debug & 8) {
 2341                 graph_check(g, TRUE);
 2342         }
 2343 #endif
 2344 
 2345         e = malloc(sizeof(struct owner_edge), M_LOCKF, M_WAITOK);
 2346 
 2347         LIST_INSERT_HEAD(&x->v_outedges, e, e_outlink);
 2348         LIST_INSERT_HEAD(&y->v_inedges, e, e_inlink);
 2349         e->e_refs = 1;
 2350         e->e_from = x;
 2351         e->e_to = y;
 2352 
 2353         return (0);
 2354 }
 2355 
 2356 /*
 2357  * Remove an edge x->y from the graph.
 2358  */
 2359 static void
 2360 graph_remove_edge(struct owner_graph *g, struct owner_vertex *x,
 2361     struct owner_vertex *y)
 2362 {
 2363         struct owner_edge *e;
 2364 
 2365         sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
 2366 
 2367         LIST_FOREACH(e, &x->v_outedges, e_outlink) {
 2368                 if (e->e_to == y)
 2369                         break;
 2370         }
 2371         KASSERT(e, ("Removing non-existent edge from deadlock graph"));
 2372 
 2373         e->e_refs--;
 2374         if (e->e_refs == 0) {
 2375 #ifdef LOCKF_DEBUG
 2376                 if (lockf_debug & 8) {
 2377                         printf("removing edge %d:", x->v_order);
 2378                         lf_print_owner(x->v_owner);
 2379                         printf(" -> %d:", y->v_order);
 2380                         lf_print_owner(y->v_owner);
 2381                         printf("\n");
 2382                 }
 2383 #endif
 2384                 LIST_REMOVE(e, e_outlink);
 2385                 LIST_REMOVE(e, e_inlink);
 2386                 free(e, M_LOCKF);
 2387         }
 2388 }
 2389 
 2390 /*
 2391  * Allocate a vertex from the free list. Return ENOMEM if there are
 2392  * none.
 2393  */
 2394 static struct owner_vertex *
 2395 graph_alloc_vertex(struct owner_graph *g, struct lock_owner *lo)
 2396 {
 2397         struct owner_vertex *v;
 2398 
 2399         sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
 2400 
 2401         v = malloc(sizeof(struct owner_vertex), M_LOCKF, M_WAITOK);
 2402         if (g->g_size == g->g_space) {
 2403                 g->g_vertices = realloc(g->g_vertices,
 2404                     2 * g->g_space * sizeof(struct owner_vertex *),
 2405                     M_LOCKF, M_WAITOK);
 2406                 free(g->g_indexbuf, M_LOCKF);
 2407                 g->g_indexbuf = malloc(2 * g->g_space * sizeof(int),
 2408                     M_LOCKF, M_WAITOK);
 2409                 g->g_space = 2 * g->g_space;
 2410         }
 2411         v->v_order = g->g_size;
 2412         v->v_gen = g->g_gen;
 2413         g->g_vertices[g->g_size] = v;
 2414         g->g_size++;
 2415 
 2416         LIST_INIT(&v->v_outedges);
 2417         LIST_INIT(&v->v_inedges);
 2418         v->v_owner = lo;
 2419 
 2420         return (v);
 2421 }
 2422 
 2423 static void
 2424 graph_free_vertex(struct owner_graph *g, struct owner_vertex *v)
 2425 {
 2426         struct owner_vertex *w;
 2427         int i;
 2428 
 2429         sx_assert(&lf_owner_graph_lock, SX_XLOCKED);
 2430         
 2431         KASSERT(LIST_EMPTY(&v->v_outedges), ("Freeing vertex with edges"));
 2432         KASSERT(LIST_EMPTY(&v->v_inedges), ("Freeing vertex with edges"));
 2433 
 2434         /*
 2435          * Remove from the graph's array and close up the gap,
 2436          * renumbering the other vertices.
 2437          */
 2438         for (i = v->v_order + 1; i < g->g_size; i++) {
 2439                 w = g->g_vertices[i];
 2440                 w->v_order--;
 2441                 g->g_vertices[i - 1] = w;
 2442         }
 2443         g->g_size--;
 2444 
 2445         free(v, M_LOCKF);
 2446 }
 2447 
 2448 static struct owner_graph *
 2449 graph_init(struct owner_graph *g)
 2450 {
 2451 
 2452         g->g_vertices = malloc(10 * sizeof(struct owner_vertex *),
 2453             M_LOCKF, M_WAITOK);
 2454         g->g_size = 0;
 2455         g->g_space = 10;
 2456         g->g_indexbuf = malloc(g->g_space * sizeof(int), M_LOCKF, M_WAITOK);
 2457         g->g_gen = 0;
 2458 
 2459         return (g);
 2460 }
 2461 
 2462 #ifdef LOCKF_DEBUG
 2463 /*
 2464  * Print description of a lock owner
 2465  */
 2466 static void
 2467 lf_print_owner(struct lock_owner *lo)
 2468 {
 2469 
 2470         if (lo->lo_flags & F_REMOTE) {
 2471                 printf("remote pid %d, system %d",
 2472                     lo->lo_pid, lo->lo_sysid);
 2473         } else if (lo->lo_flags & F_FLOCK) {
 2474                 printf("file %p", lo->lo_id);
 2475         } else {
 2476                 printf("local pid %d", lo->lo_pid);
 2477         }
 2478 }
 2479 
 2480 /*
 2481  * Print out a lock.
 2482  */
 2483 static void
 2484 lf_print(char *tag, struct lockf_entry *lock)
 2485 {
 2486 
 2487         printf("%s: lock %p for ", tag, (void *)lock);
 2488         lf_print_owner(lock->lf_owner);
 2489         if (lock->lf_inode != (struct inode *)0)
 2490                 printf(" in ino %ju on dev <%s>,",
 2491                     (uintmax_t)lock->lf_inode->i_number,
 2492                     devtoname(lock->lf_inode->i_dev));
 2493         printf(" %s, start %jd, end ",
 2494             lock->lf_type == F_RDLCK ? "shared" :
 2495             lock->lf_type == F_WRLCK ? "exclusive" :
 2496             lock->lf_type == F_UNLCK ? "unlock" : "unknown",
 2497             (intmax_t)lock->lf_start);
 2498         if (lock->lf_end == OFF_MAX)
 2499                 printf("EOF");
 2500         else
 2501                 printf("%jd", (intmax_t)lock->lf_end);
 2502         if (!LIST_EMPTY(&lock->lf_outedges))
 2503                 printf(" block %p\n",
 2504                     (void *)LIST_FIRST(&lock->lf_outedges)->le_to);
 2505         else
 2506                 printf("\n");
 2507 }
 2508 
 2509 static void
 2510 lf_printlist(char *tag, struct lockf_entry *lock)
 2511 {
 2512         struct lockf_entry *lf, *blk;
 2513         struct lockf_edge *e;
 2514 
 2515         if (lock->lf_inode == (struct inode *)0)
 2516                 return;
 2517 
 2518         printf("%s: Lock list for ino %ju on dev <%s>:\n",
 2519             tag, (uintmax_t)lock->lf_inode->i_number,
 2520             devtoname(lock->lf_inode->i_dev));
 2521         LIST_FOREACH(lf, &lock->lf_vnode->v_lockf->ls_active, lf_link) {
 2522                 printf("\tlock %p for ",(void *)lf);
 2523                 lf_print_owner(lock->lf_owner);
 2524                 printf(", %s, start %jd, end %jd",
 2525                     lf->lf_type == F_RDLCK ? "shared" :
 2526                     lf->lf_type == F_WRLCK ? "exclusive" :
 2527                     lf->lf_type == F_UNLCK ? "unlock" :
 2528                     "unknown", (intmax_t)lf->lf_start, (intmax_t)lf->lf_end);
 2529                 LIST_FOREACH(e, &lf->lf_outedges, le_outlink) {
 2530                         blk = e->le_to;
 2531                         printf("\n\t\tlock request %p for ", (void *)blk);
 2532                         lf_print_owner(blk->lf_owner);
 2533                         printf(", %s, start %jd, end %jd",
 2534                             blk->lf_type == F_RDLCK ? "shared" :
 2535                             blk->lf_type == F_WRLCK ? "exclusive" :
 2536                             blk->lf_type == F_UNLCK ? "unlock" :
 2537                             "unknown", (intmax_t)blk->lf_start,
 2538                             (intmax_t)blk->lf_end);
 2539                         if (!LIST_EMPTY(&blk->lf_inedges))
 2540                                 panic("lf_printlist: bad list");
 2541                 }
 2542                 printf("\n");
 2543         }
 2544 }
 2545 #endif /* LOCKF_DEBUG */

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