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

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    1 /*-
    2  * Copyright (c) 2000-2003 Tor Egge
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  */
   26 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: releng/10.0/sys/ufs/ffs/ffs_rawread.c 248515 2013-03-19 14:43:57Z kib $");
   29 
   30 #include <sys/param.h>
   31 #include <sys/systm.h>
   32 #include <sys/fcntl.h>
   33 #include <sys/file.h>
   34 #include <sys/stat.h>
   35 #include <sys/proc.h>
   36 #include <sys/limits.h>
   37 #include <sys/mount.h>
   38 #include <sys/namei.h>
   39 #include <sys/vnode.h>
   40 #include <sys/conf.h>
   41 #include <sys/filio.h>
   42 #include <sys/ttycom.h>
   43 #include <sys/bio.h>
   44 #include <sys/buf.h>
   45 #include <sys/rwlock.h>
   46 #include <ufs/ufs/extattr.h>
   47 #include <ufs/ufs/quota.h>
   48 #include <ufs/ufs/inode.h>
   49 #include <ufs/ufs/ufsmount.h>
   50 #include <ufs/ufs/ufs_extern.h>
   51 #include <ufs/ffs/fs.h>
   52 #include <ufs/ffs/ffs_extern.h>
   53 
   54 #include <vm/vm.h>
   55 #include <vm/vm_extern.h>
   56 #include <vm/vm_object.h>
   57 #include <sys/kernel.h>
   58 #include <sys/sysctl.h>
   59 
   60 static int ffs_rawread_readahead(struct vnode *vp,
   61                                  caddr_t udata,
   62                                  off_t offset,
   63                                  size_t len,
   64                                  struct thread *td,
   65                                  struct buf *bp,
   66                                  caddr_t sa);
   67 static int ffs_rawread_main(struct vnode *vp,
   68                             struct uio *uio);
   69 
   70 static int ffs_rawread_sync(struct vnode *vp);
   71 
   72 int ffs_rawread(struct vnode *vp, struct uio *uio, int *workdone);
   73 
   74 void ffs_rawread_setup(void);
   75 
   76 SYSCTL_DECL(_vfs_ffs);
   77 
   78 static int ffsrawbufcnt = 4;
   79 SYSCTL_INT(_vfs_ffs, OID_AUTO, ffsrawbufcnt, CTLFLAG_RD, &ffsrawbufcnt, 0,
   80            "Buffers available for raw reads");
   81 
   82 static int allowrawread = 1;
   83 SYSCTL_INT(_vfs_ffs, OID_AUTO, allowrawread, CTLFLAG_RW, &allowrawread, 0,
   84            "Flag to enable raw reads");
   85 
   86 static int rawreadahead = 1;
   87 SYSCTL_INT(_vfs_ffs, OID_AUTO, rawreadahead, CTLFLAG_RW, &rawreadahead, 0,
   88            "Flag to enable readahead for long raw reads");
   89 
   90 
   91 void
   92 ffs_rawread_setup(void)
   93 {
   94         ffsrawbufcnt = (nswbuf > 100 ) ? (nswbuf - (nswbuf >> 4)) : nswbuf - 8;
   95 }
   96 
   97 
   98 static int
   99 ffs_rawread_sync(struct vnode *vp)
  100 {
  101         int error;
  102         int upgraded;
  103         struct bufobj *bo;
  104         struct mount *mp;
  105         vm_object_t obj;
  106 
  107         /* Check for dirty mmap, pending writes and dirty buffers */
  108         bo = &vp->v_bufobj;
  109         BO_LOCK(bo);
  110         VI_LOCK(vp);
  111         if (bo->bo_numoutput > 0 ||
  112             bo->bo_dirty.bv_cnt > 0 ||
  113             ((obj = vp->v_object) != NULL &&
  114              (obj->flags & OBJ_MIGHTBEDIRTY) != 0)) {
  115                 VI_UNLOCK(vp);
  116                 BO_UNLOCK(bo);
  117                 
  118                 if (vn_start_write(vp, &mp, V_NOWAIT) != 0) {
  119                         if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE)
  120                                 upgraded = 1;
  121                         else
  122                                 upgraded = 0;
  123                         VOP_UNLOCK(vp, 0);
  124                         (void) vn_start_write(vp, &mp, V_WAIT);
  125                         VOP_LOCK(vp, LK_EXCLUSIVE);
  126                 } else if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE) {
  127                         upgraded = 1;
  128                         /* Upgrade to exclusive lock, this might block */
  129                         VOP_LOCK(vp, LK_UPGRADE);
  130                 } else
  131                         upgraded = 0;
  132                         
  133                 
  134                 VI_LOCK(vp);
  135                 /* Check if vnode was reclaimed while unlocked. */
  136                 if ((vp->v_iflag & VI_DOOMED) != 0) {
  137                         VI_UNLOCK(vp);
  138                         if (upgraded != 0)
  139                                 VOP_LOCK(vp, LK_DOWNGRADE);
  140                         vn_finished_write(mp);
  141                         return (EIO);
  142                 }
  143                 /* Attempt to msync mmap() regions to clean dirty mmap */ 
  144                 if ((obj = vp->v_object) != NULL &&
  145                     (obj->flags & OBJ_MIGHTBEDIRTY) != 0) {
  146                         VI_UNLOCK(vp);
  147                         VM_OBJECT_WLOCK(obj);
  148                         vm_object_page_clean(obj, 0, 0, OBJPC_SYNC);
  149                         VM_OBJECT_WUNLOCK(obj);
  150                 } else
  151                         VI_UNLOCK(vp);
  152 
  153                 /* Wait for pending writes to complete */
  154                 BO_LOCK(bo);
  155                 error = bufobj_wwait(&vp->v_bufobj, 0, 0);
  156                 if (error != 0) {
  157                         /* XXX: can't happen with a zero timeout ??? */
  158                         BO_UNLOCK(bo);
  159                         if (upgraded != 0)
  160                                 VOP_LOCK(vp, LK_DOWNGRADE);
  161                         vn_finished_write(mp);
  162                         return (error);
  163                 }
  164                 /* Flush dirty buffers */
  165                 if (bo->bo_dirty.bv_cnt > 0) {
  166                         BO_UNLOCK(bo);
  167                         if ((error = ffs_syncvnode(vp, MNT_WAIT, 0)) != 0) {
  168                                 if (upgraded != 0)
  169                                         VOP_LOCK(vp, LK_DOWNGRADE);
  170                                 vn_finished_write(mp);
  171                                 return (error);
  172                         }
  173                         BO_LOCK(bo);
  174                         if (bo->bo_numoutput > 0 || bo->bo_dirty.bv_cnt > 0)
  175                                 panic("ffs_rawread_sync: dirty bufs");
  176                 }
  177                 BO_UNLOCK(bo);
  178                 if (upgraded != 0)
  179                         VOP_LOCK(vp, LK_DOWNGRADE);
  180                 vn_finished_write(mp);
  181         } else {
  182                 VI_UNLOCK(vp);
  183                 BO_UNLOCK(bo);
  184         }
  185         return 0;
  186 }
  187 
  188 
  189 static int
  190 ffs_rawread_readahead(struct vnode *vp,
  191                       caddr_t udata,
  192                       off_t offset,
  193                       size_t len,
  194                       struct thread *td,
  195                       struct buf *bp,
  196                       caddr_t sa)
  197 {
  198         int error;
  199         u_int iolen;
  200         off_t blockno;
  201         int blockoff;
  202         int bsize;
  203         struct vnode *dp;
  204         int bforwards;
  205         struct inode *ip;
  206         ufs2_daddr_t blkno;
  207         
  208         bsize = vp->v_mount->mnt_stat.f_iosize;
  209         
  210         ip = VTOI(vp);
  211         dp = ip->i_devvp;
  212 
  213         iolen = ((vm_offset_t) udata) & PAGE_MASK;
  214         bp->b_bcount = len;
  215         if (bp->b_bcount + iolen > bp->b_kvasize) {
  216                 bp->b_bcount = bp->b_kvasize;
  217                 if (iolen != 0)
  218                         bp->b_bcount -= PAGE_SIZE;
  219         }
  220         bp->b_flags = 0;        /* XXX necessary ? */
  221         bp->b_iocmd = BIO_READ;
  222         bp->b_iodone = bdone;
  223         bp->b_data = udata;
  224         bp->b_saveaddr = sa;
  225         blockno = offset / bsize;
  226         blockoff = (offset % bsize) / DEV_BSIZE;
  227         if ((daddr_t) blockno != blockno) {
  228                 return EINVAL; /* blockno overflow */
  229         }
  230         
  231         bp->b_lblkno = bp->b_blkno = blockno;
  232         
  233         error = ufs_bmaparray(vp, bp->b_lblkno, &blkno, NULL, &bforwards, NULL);
  234         if (error != 0)
  235                 return error;
  236         if (blkno == -1) {
  237 
  238                 /* Fill holes with NULs to preserve semantics */
  239                 
  240                 if (bp->b_bcount + blockoff * DEV_BSIZE > bsize)
  241                         bp->b_bcount = bsize - blockoff * DEV_BSIZE;
  242                 bp->b_bufsize = bp->b_bcount;
  243                 
  244                 if (vmapbuf(bp, 1) < 0)
  245                         return EFAULT;
  246                 
  247                 maybe_yield();
  248                 bzero(bp->b_data, bp->b_bufsize);
  249 
  250                 /* Mark operation completed (similar to bufdone()) */
  251 
  252                 bp->b_resid = 0;
  253                 bp->b_flags |= B_DONE;
  254                 return 0;
  255         }
  256         bp->b_blkno = blkno + blockoff;
  257         bp->b_offset = bp->b_iooffset = (blkno + blockoff) * DEV_BSIZE;
  258         
  259         if (bp->b_bcount + blockoff * DEV_BSIZE > bsize * (1 + bforwards))
  260                 bp->b_bcount = bsize * (1 + bforwards) - blockoff * DEV_BSIZE;
  261         bp->b_bufsize = bp->b_bcount;
  262         
  263         if (vmapbuf(bp, 1) < 0)
  264                 return EFAULT;
  265         
  266         BO_STRATEGY(&dp->v_bufobj, bp);
  267         return 0;
  268 }
  269 
  270 
  271 static int
  272 ffs_rawread_main(struct vnode *vp,
  273                  struct uio *uio)
  274 {
  275         int error, nerror;
  276         struct buf *bp, *nbp, *tbp;
  277         caddr_t sa, nsa, tsa;
  278         u_int iolen;
  279         int spl;
  280         caddr_t udata;
  281         long resid;
  282         off_t offset;
  283         struct thread *td;
  284         
  285         td = uio->uio_td ? uio->uio_td : curthread;
  286         udata = uio->uio_iov->iov_base;
  287         resid = uio->uio_resid;
  288         offset = uio->uio_offset;
  289 
  290         /*
  291          * keep the process from being swapped
  292          */
  293         PHOLD(td->td_proc);
  294         
  295         error = 0;
  296         nerror = 0;
  297         
  298         bp = NULL;
  299         nbp = NULL;
  300         sa = NULL;
  301         nsa = NULL;
  302         
  303         while (resid > 0) {
  304                 
  305                 if (bp == NULL) { /* Setup first read */
  306                         /* XXX: Leave some bufs for swap */
  307                         bp = getpbuf(&ffsrawbufcnt);
  308                         sa = bp->b_data;
  309                         pbgetvp(vp, bp);
  310                         error = ffs_rawread_readahead(vp, udata, offset,
  311                                                      resid, td, bp, sa);
  312                         if (error != 0)
  313                                 break;
  314                         
  315                         if (resid > bp->b_bufsize) { /* Setup fist readahead */
  316                                 /* XXX: Leave bufs for swap */
  317                                 if (rawreadahead != 0) 
  318                                         nbp = trypbuf(&ffsrawbufcnt);
  319                                 else
  320                                         nbp = NULL;
  321                                 if (nbp != NULL) {
  322                                         nsa = nbp->b_data;
  323                                         pbgetvp(vp, nbp);
  324                                         
  325                                         nerror = ffs_rawread_readahead(vp, 
  326                                                                        udata +
  327                                                                        bp->b_bufsize,
  328                                                                        offset +
  329                                                                        bp->b_bufsize,
  330                                                                        resid -
  331                                                                        bp->b_bufsize,
  332                                                                        td,
  333                                                                        nbp,
  334                                                                        nsa);
  335                                         if (nerror) {
  336                                                 pbrelvp(nbp);
  337                                                 relpbuf(nbp, &ffsrawbufcnt);
  338                                                 nbp = NULL;
  339                                         }
  340                                 }
  341                         }
  342                 }
  343                 
  344                 spl = splbio();
  345                 bwait(bp, PRIBIO, "rawrd");
  346                 splx(spl);
  347                 
  348                 vunmapbuf(bp);
  349                 
  350                 iolen = bp->b_bcount - bp->b_resid;
  351                 if (iolen == 0 && (bp->b_ioflags & BIO_ERROR) == 0) {
  352                         nerror = 0;     /* Ignore possible beyond EOF error */
  353                         break; /* EOF */
  354                 }
  355                 
  356                 if ((bp->b_ioflags & BIO_ERROR) != 0) {
  357                         error = bp->b_error;
  358                         break;
  359                 }
  360                 resid -= iolen;
  361                 udata += iolen;
  362                 offset += iolen;
  363                 if (iolen < bp->b_bufsize) {
  364                         /* Incomplete read.  Try to read remaining part */
  365                         error = ffs_rawread_readahead(vp,
  366                                                       udata,
  367                                                       offset,
  368                                                       bp->b_bufsize - iolen,
  369                                                       td,
  370                                                       bp,
  371                                                       sa);
  372                         if (error != 0)
  373                                 break;
  374                 } else if (nbp != NULL) { /* Complete read with readahead */
  375                         
  376                         tbp = bp;
  377                         bp = nbp;
  378                         nbp = tbp;
  379                         
  380                         tsa = sa;
  381                         sa = nsa;
  382                         nsa = tsa;
  383                         
  384                         if (resid <= bp->b_bufsize) { /* No more readaheads */
  385                                 pbrelvp(nbp);
  386                                 relpbuf(nbp, &ffsrawbufcnt);
  387                                 nbp = NULL;
  388                         } else { /* Setup next readahead */
  389                                 nerror = ffs_rawread_readahead(vp,
  390                                                                udata +
  391                                                                bp->b_bufsize,
  392                                                                offset +
  393                                                                bp->b_bufsize,
  394                                                                resid -
  395                                                                bp->b_bufsize,
  396                                                                td,
  397                                                                nbp,
  398                                                                nsa);
  399                                 if (nerror != 0) {
  400                                         pbrelvp(nbp);
  401                                         relpbuf(nbp, &ffsrawbufcnt);
  402                                         nbp = NULL;
  403                                 }
  404                         }
  405                 } else if (nerror != 0) {/* Deferred Readahead error */
  406                         break;          
  407                 }  else if (resid > 0) { /* More to read, no readahead */
  408                         error = ffs_rawread_readahead(vp, udata, offset,
  409                                                       resid, td, bp, sa);
  410                         if (error != 0)
  411                                 break;
  412                 }
  413         }
  414         
  415         if (bp != NULL) {
  416                 pbrelvp(bp);
  417                 relpbuf(bp, &ffsrawbufcnt);
  418         }
  419         if (nbp != NULL) {                      /* Run down readahead buffer */
  420                 spl = splbio();
  421                 bwait(nbp, PRIBIO, "rawrd");
  422                 splx(spl);
  423                 vunmapbuf(nbp);
  424                 pbrelvp(nbp);
  425                 relpbuf(nbp, &ffsrawbufcnt);
  426         }
  427         
  428         if (error == 0)
  429                 error = nerror;
  430         PRELE(td->td_proc);
  431         uio->uio_iov->iov_base = udata;
  432         uio->uio_resid = resid;
  433         uio->uio_offset = offset;
  434         return error;
  435 }
  436 
  437 
  438 int
  439 ffs_rawread(struct vnode *vp,
  440             struct uio *uio,
  441             int *workdone)
  442 {
  443         if (allowrawread != 0 &&
  444             uio->uio_iovcnt == 1 && 
  445             uio->uio_segflg == UIO_USERSPACE &&
  446             uio->uio_resid == uio->uio_iov->iov_len &&
  447             (((uio->uio_td != NULL) ? uio->uio_td : curthread)->td_pflags &
  448              TDP_DEADLKTREAT) == 0) {
  449                 int secsize;            /* Media sector size */
  450                 off_t filebytes;        /* Bytes left of file */
  451                 int blockbytes;         /* Bytes left of file in full blocks */
  452                 int partialbytes;       /* Bytes in last partial block */
  453                 int skipbytes;          /* Bytes not to read in ffs_rawread */
  454                 struct inode *ip;
  455                 int error;
  456                 
  457 
  458                 /* Only handle sector aligned reads */
  459                 ip = VTOI(vp);
  460                 secsize = ip->i_devvp->v_bufobj.bo_bsize;
  461                 if ((uio->uio_offset & (secsize - 1)) == 0 &&
  462                     (uio->uio_resid & (secsize - 1)) == 0) {
  463                         
  464                         /* Sync dirty pages and buffers if needed */
  465                         error = ffs_rawread_sync(vp);
  466                         if (error != 0)
  467                                 return error;
  468                         
  469                         /* Check for end of file */
  470                         if (ip->i_size > uio->uio_offset) {
  471                                 filebytes = ip->i_size - uio->uio_offset;
  472 
  473                                 /* No special eof handling needed ? */
  474                                 if (uio->uio_resid <= filebytes) {
  475                                         *workdone = 1;
  476                                         return ffs_rawread_main(vp, uio);
  477                                 }
  478                                 
  479                                 partialbytes = ((unsigned int) ip->i_size) %
  480                                         ip->i_fs->fs_bsize;
  481                                 blockbytes = (int) filebytes - partialbytes;
  482                                 if (blockbytes > 0) {
  483                                         skipbytes = uio->uio_resid -
  484                                                 blockbytes;
  485                                         uio->uio_resid = blockbytes;
  486                                         error = ffs_rawread_main(vp, uio);
  487                                         uio->uio_resid += skipbytes;
  488                                         if (error != 0)
  489                                                 return error;
  490                                         /* Read remaining part using buffer */
  491                                 }
  492                         }
  493                 }
  494         }
  495         *workdone = 0;
  496         return 0;
  497 }

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