The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/fs/pnode.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    1 /*
    2  *  linux/fs/pnode.c
    3  *
    4  * (C) Copyright IBM Corporation 2005.
    5  *      Released under GPL v2.
    6  *      Author : Ram Pai (linuxram@us.ibm.com)
    7  *
    8  */
    9 #include <linux/mnt_namespace.h>
   10 #include <linux/mount.h>
   11 #include <linux/fs.h>
   12 #include "internal.h"
   13 #include "pnode.h"
   14 
   15 /* return the next shared peer mount of @p */
   16 static inline struct mount *next_peer(struct mount *p)
   17 {
   18         return list_entry(p->mnt_share.next, struct mount, mnt_share);
   19 }
   20 
   21 static inline struct mount *first_slave(struct mount *p)
   22 {
   23         return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);
   24 }
   25 
   26 static inline struct mount *next_slave(struct mount *p)
   27 {
   28         return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
   29 }
   30 
   31 static struct mount *get_peer_under_root(struct mount *mnt,
   32                                          struct mnt_namespace *ns,
   33                                          const struct path *root)
   34 {
   35         struct mount *m = mnt;
   36 
   37         do {
   38                 /* Check the namespace first for optimization */
   39                 if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root))
   40                         return m;
   41 
   42                 m = next_peer(m);
   43         } while (m != mnt);
   44 
   45         return NULL;
   46 }
   47 
   48 /*
   49  * Get ID of closest dominating peer group having a representative
   50  * under the given root.
   51  *
   52  * Caller must hold namespace_sem
   53  */
   54 int get_dominating_id(struct mount *mnt, const struct path *root)
   55 {
   56         struct mount *m;
   57 
   58         for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
   59                 struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root);
   60                 if (d)
   61                         return d->mnt_group_id;
   62         }
   63 
   64         return 0;
   65 }
   66 
   67 static int do_make_slave(struct mount *mnt)
   68 {
   69         struct mount *peer_mnt = mnt, *master = mnt->mnt_master;
   70         struct mount *slave_mnt;
   71 
   72         /*
   73          * slave 'mnt' to a peer mount that has the
   74          * same root dentry. If none is available then
   75          * slave it to anything that is available.
   76          */
   77         while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
   78                peer_mnt->mnt.mnt_root != mnt->mnt.mnt_root) ;
   79 
   80         if (peer_mnt == mnt) {
   81                 peer_mnt = next_peer(mnt);
   82                 if (peer_mnt == mnt)
   83                         peer_mnt = NULL;
   84         }
   85         if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
   86                 mnt_release_group_id(mnt);
   87 
   88         list_del_init(&mnt->mnt_share);
   89         mnt->mnt_group_id = 0;
   90 
   91         if (peer_mnt)
   92                 master = peer_mnt;
   93 
   94         if (master) {
   95                 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
   96                         slave_mnt->mnt_master = master;
   97                 list_move(&mnt->mnt_slave, &master->mnt_slave_list);
   98                 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
   99                 INIT_LIST_HEAD(&mnt->mnt_slave_list);
  100         } else {
  101                 struct list_head *p = &mnt->mnt_slave_list;
  102                 while (!list_empty(p)) {
  103                         slave_mnt = list_first_entry(p,
  104                                         struct mount, mnt_slave);
  105                         list_del_init(&slave_mnt->mnt_slave);
  106                         slave_mnt->mnt_master = NULL;
  107                 }
  108         }
  109         mnt->mnt_master = master;
  110         CLEAR_MNT_SHARED(mnt);
  111         return 0;
  112 }
  113 
  114 /*
  115  * vfsmount lock must be held for write
  116  */
  117 void change_mnt_propagation(struct mount *mnt, int type)
  118 {
  119         if (type == MS_SHARED) {
  120                 set_mnt_shared(mnt);
  121                 return;
  122         }
  123         do_make_slave(mnt);
  124         if (type != MS_SLAVE) {
  125                 list_del_init(&mnt->mnt_slave);
  126                 mnt->mnt_master = NULL;
  127                 if (type == MS_UNBINDABLE)
  128                         mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
  129                 else
  130                         mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
  131         }
  132 }
  133 
  134 /*
  135  * get the next mount in the propagation tree.
  136  * @m: the mount seen last
  137  * @origin: the original mount from where the tree walk initiated
  138  *
  139  * Note that peer groups form contiguous segments of slave lists.
  140  * We rely on that in get_source() to be able to find out if
  141  * vfsmount found while iterating with propagation_next() is
  142  * a peer of one we'd found earlier.
  143  */
  144 static struct mount *propagation_next(struct mount *m,
  145                                          struct mount *origin)
  146 {
  147         /* are there any slaves of this mount? */
  148         if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
  149                 return first_slave(m);
  150 
  151         while (1) {
  152                 struct mount *master = m->mnt_master;
  153 
  154                 if (master == origin->mnt_master) {
  155                         struct mount *next = next_peer(m);
  156                         return (next == origin) ? NULL : next;
  157                 } else if (m->mnt_slave.next != &master->mnt_slave_list)
  158                         return next_slave(m);
  159 
  160                 /* back at master */
  161                 m = master;
  162         }
  163 }
  164 
  165 /*
  166  * return the source mount to be used for cloning
  167  *
  168  * @dest        the current destination mount
  169  * @last_dest   the last seen destination mount
  170  * @last_src    the last seen source mount
  171  * @type        return CL_SLAVE if the new mount has to be
  172  *              cloned as a slave.
  173  */
  174 static struct mount *get_source(struct mount *dest,
  175                                 struct mount *last_dest,
  176                                 struct mount *last_src,
  177                                 int *type)
  178 {
  179         struct mount *p_last_src = NULL;
  180         struct mount *p_last_dest = NULL;
  181 
  182         while (last_dest != dest->mnt_master) {
  183                 p_last_dest = last_dest;
  184                 p_last_src = last_src;
  185                 last_dest = last_dest->mnt_master;
  186                 last_src = last_src->mnt_master;
  187         }
  188 
  189         if (p_last_dest) {
  190                 do {
  191                         p_last_dest = next_peer(p_last_dest);
  192                 } while (IS_MNT_NEW(p_last_dest));
  193                 /* is that a peer of the earlier? */
  194                 if (dest == p_last_dest) {
  195                         *type = CL_MAKE_SHARED;
  196                         return p_last_src;
  197                 }
  198         }
  199         /* slave of the earlier, then */
  200         *type = CL_SLAVE;
  201         /* beginning of peer group among the slaves? */
  202         if (IS_MNT_SHARED(dest))
  203                 *type |= CL_MAKE_SHARED;
  204         return last_src;
  205 }
  206 
  207 /*
  208  * mount 'source_mnt' under the destination 'dest_mnt' at
  209  * dentry 'dest_dentry'. And propagate that mount to
  210  * all the peer and slave mounts of 'dest_mnt'.
  211  * Link all the new mounts into a propagation tree headed at
  212  * source_mnt. Also link all the new mounts using ->mnt_list
  213  * headed at source_mnt's ->mnt_list
  214  *
  215  * @dest_mnt: destination mount.
  216  * @dest_dentry: destination dentry.
  217  * @source_mnt: source mount.
  218  * @tree_list : list of heads of trees to be attached.
  219  */
  220 int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
  221                     struct mount *source_mnt, struct list_head *tree_list)
  222 {
  223         struct mount *m, *child;
  224         int ret = 0;
  225         struct mount *prev_dest_mnt = dest_mnt;
  226         struct mount *prev_src_mnt  = source_mnt;
  227         LIST_HEAD(tmp_list);
  228         LIST_HEAD(umount_list);
  229 
  230         for (m = propagation_next(dest_mnt, dest_mnt); m;
  231                         m = propagation_next(m, dest_mnt)) {
  232                 int type;
  233                 struct mount *source;
  234 
  235                 if (IS_MNT_NEW(m))
  236                         continue;
  237 
  238                 source =  get_source(m, prev_dest_mnt, prev_src_mnt, &type);
  239 
  240                 child = copy_tree(source, source->mnt.mnt_root, type);
  241                 if (IS_ERR(child)) {
  242                         ret = PTR_ERR(child);
  243                         list_splice(tree_list, tmp_list.prev);
  244                         goto out;
  245                 }
  246 
  247                 if (is_subdir(dest_dentry, m->mnt.mnt_root)) {
  248                         mnt_set_mountpoint(m, dest_dentry, child);
  249                         list_add_tail(&child->mnt_hash, tree_list);
  250                 } else {
  251                         /*
  252                          * This can happen if the parent mount was bind mounted
  253                          * on some subdirectory of a shared/slave mount.
  254                          */
  255                         list_add_tail(&child->mnt_hash, &tmp_list);
  256                 }
  257                 prev_dest_mnt = m;
  258                 prev_src_mnt  = child;
  259         }
  260 out:
  261         br_write_lock(&vfsmount_lock);
  262         while (!list_empty(&tmp_list)) {
  263                 child = list_first_entry(&tmp_list, struct mount, mnt_hash);
  264                 umount_tree(child, 0, &umount_list);
  265         }
  266         br_write_unlock(&vfsmount_lock);
  267         release_mounts(&umount_list);
  268         return ret;
  269 }
  270 
  271 /*
  272  * return true if the refcount is greater than count
  273  */
  274 static inline int do_refcount_check(struct mount *mnt, int count)
  275 {
  276         int mycount = mnt_get_count(mnt) - mnt->mnt_ghosts;
  277         return (mycount > count);
  278 }
  279 
  280 /*
  281  * check if the mount 'mnt' can be unmounted successfully.
  282  * @mnt: the mount to be checked for unmount
  283  * NOTE: unmounting 'mnt' would naturally propagate to all
  284  * other mounts its parent propagates to.
  285  * Check if any of these mounts that **do not have submounts**
  286  * have more references than 'refcnt'. If so return busy.
  287  *
  288  * vfsmount lock must be held for write
  289  */
  290 int propagate_mount_busy(struct mount *mnt, int refcnt)
  291 {
  292         struct mount *m, *child;
  293         struct mount *parent = mnt->mnt_parent;
  294         int ret = 0;
  295 
  296         if (mnt == parent)
  297                 return do_refcount_check(mnt, refcnt);
  298 
  299         /*
  300          * quickly check if the current mount can be unmounted.
  301          * If not, we don't have to go checking for all other
  302          * mounts
  303          */
  304         if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
  305                 return 1;
  306 
  307         for (m = propagation_next(parent, parent); m;
  308                         m = propagation_next(m, parent)) {
  309                 child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint, 0);
  310                 if (child && list_empty(&child->mnt_mounts) &&
  311                     (ret = do_refcount_check(child, 1)))
  312                         break;
  313         }
  314         return ret;
  315 }
  316 
  317 /*
  318  * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
  319  * parent propagates to.
  320  */
  321 static void __propagate_umount(struct mount *mnt)
  322 {
  323         struct mount *parent = mnt->mnt_parent;
  324         struct mount *m;
  325 
  326         BUG_ON(parent == mnt);
  327 
  328         for (m = propagation_next(parent, parent); m;
  329                         m = propagation_next(m, parent)) {
  330 
  331                 struct mount *child = __lookup_mnt(&m->mnt,
  332                                         mnt->mnt_mountpoint, 0);
  333                 /*
  334                  * umount the child only if the child has no
  335                  * other children
  336                  */
  337                 if (child && list_empty(&child->mnt_mounts))
  338                         list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
  339         }
  340 }
  341 
  342 /*
  343  * collect all mounts that receive propagation from the mount in @list,
  344  * and return these additional mounts in the same list.
  345  * @list: the list of mounts to be unmounted.
  346  *
  347  * vfsmount lock must be held for write
  348  */
  349 int propagate_umount(struct list_head *list)
  350 {
  351         struct mount *mnt;
  352 
  353         list_for_each_entry(mnt, list, mnt_hash)
  354                 __propagate_umount(mnt);
  355         return 0;
  356 }

Cache object: ca4b5f5d545a1189d2573d59ea8c566e


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.