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


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FreeBSD/Linux Kernel Cross Reference
sys/fs/ext2fs/ext2_bmap.c

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    1 /*-
    2  * Copyright (c) 1989, 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  * (c) UNIX System Laboratories, Inc.
    5  * All or some portions of this file are derived from material licensed
    6  * to the University of California by American Telephone and Telegraph
    7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
    8  * the permission of UNIX System Laboratories, Inc.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)ufs_bmap.c  8.7 (Berkeley) 3/21/95
   35  * $FreeBSD: releng/9.1/sys/fs/ext2fs/ext2_bmap.c 229549 2012-01-05 01:35:01Z pfg $
   36  */
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h>
   40 #include <sys/bio.h>
   41 #include <sys/buf.h>
   42 #include <sys/proc.h>
   43 #include <sys/vnode.h>
   44 #include <sys/mount.h>
   45 #include <sys/resourcevar.h>
   46 #include <sys/stat.h>
   47 
   48 #include <fs/ext2fs/inode.h>
   49 #include <fs/ext2fs/ext2fs.h>
   50 #include <fs/ext2fs/ext2_mount.h>
   51 #include <fs/ext2fs/ext2_extern.h>
   52 
   53 /*
   54  * Bmap converts the logical block number of a file to its physical block
   55  * number on the disk. The conversion is done by using the logical block
   56  * number to index into the array of block pointers described by the dinode.
   57  */
   58 int
   59 ext2_bmap(ap)
   60         struct vop_bmap_args /* {
   61                 struct vnode *a_vp;
   62                 daddr_t a_bn;
   63                 struct bufobj **a_bop;
   64                 daddr_t *a_bnp;
   65                 int *a_runp;
   66                 int *a_runb;
   67         } */ *ap;
   68 {
   69         int32_t blkno;
   70         int error;
   71 
   72         /*
   73          * Check for underlying vnode requests and ensure that logical
   74          * to physical mapping is requested.
   75          */
   76         if (ap->a_bop != NULL)
   77                 *ap->a_bop = &VTOI(ap->a_vp)->i_devvp->v_bufobj;
   78         if (ap->a_bnp == NULL)
   79                 return (0);
   80 
   81         error = ext2_bmaparray(ap->a_vp, ap->a_bn, &blkno,
   82             ap->a_runp, ap->a_runb);
   83         *ap->a_bnp = blkno;
   84         return (error);
   85 }
   86 
   87 /*
   88  * Indirect blocks are now on the vnode for the file.  They are given negative
   89  * logical block numbers.  Indirect blocks are addressed by the negative
   90  * address of the first data block to which they point.  Double indirect blocks
   91  * are addressed by one less than the address of the first indirect block to
   92  * which they point.  Triple indirect blocks are addressed by one less than
   93  * the address of the first double indirect block to which they point.
   94  *
   95  * ext2_bmaparray does the bmap conversion, and if requested returns the
   96  * array of logical blocks which must be traversed to get to a block.
   97  * Each entry contains the offset into that block that gets you to the
   98  * next block and the disk address of the block (if it is assigned).
   99  */
  100 
  101 int
  102 ext2_bmaparray(vp, bn, bnp, runp, runb)
  103         struct vnode *vp;
  104         int32_t bn;
  105         int32_t *bnp;
  106         int *runp;
  107         int *runb;
  108 {
  109         struct inode *ip;
  110         struct buf *bp;
  111         struct ext2mount *ump;
  112         struct mount *mp;
  113         struct vnode *devvp;
  114         struct indir a[NIADDR+1], *ap;
  115         int32_t daddr;
  116         long metalbn;
  117         int error, num, maxrun = 0, bsize;
  118         int *nump;
  119 
  120         ap = NULL;
  121         ip = VTOI(vp);
  122         mp = vp->v_mount;
  123         ump = VFSTOEXT2(mp);
  124         devvp = ump->um_devvp;
  125 
  126         bsize = EXT2_BLOCK_SIZE(ump->um_e2fs);
  127 
  128         if (runp) {
  129                 maxrun = mp->mnt_iosize_max / bsize - 1;
  130                 *runp = 0;
  131         }
  132 
  133         if (runb) {
  134                 *runb = 0;
  135         }
  136 
  137 
  138         ap = a;
  139         nump = &num;
  140         error = ext2_getlbns(vp, bn, ap, nump);
  141         if (error)
  142                 return (error);
  143 
  144         num = *nump;
  145         if (num == 0) {
  146                 *bnp = blkptrtodb(ump, ip->i_db[bn]);
  147                 if (*bnp == 0) {
  148                         *bnp = -1;
  149                 } else if (runp) {
  150                         int32_t bnb = bn;
  151                         for (++bn; bn < NDADDR && *runp < maxrun &&
  152                             is_sequential(ump, ip->i_db[bn - 1], ip->i_db[bn]);
  153                             ++bn, ++*runp);
  154                         bn = bnb;
  155                         if (runb && (bn > 0)) {
  156                                 for (--bn; (bn >= 0) && (*runb < maxrun) &&
  157                                         is_sequential(ump, ip->i_db[bn],
  158                                                 ip->i_db[bn+1]);
  159                                                 --bn, ++*runb);
  160                         }
  161                 }
  162                 return (0);
  163         }
  164 
  165 
  166         /* Get disk address out of indirect block array */
  167         daddr = ip->i_ib[ap->in_off];
  168 
  169         for (bp = NULL, ++ap; --num; ++ap) {
  170                 /*
  171                  * Exit the loop if there is no disk address assigned yet and
  172                  * the indirect block isn't in the cache, or if we were
  173                  * looking for an indirect block and we've found it.
  174                  */
  175 
  176                 metalbn = ap->in_lbn;
  177                 if ((daddr == 0 && !incore(&vp->v_bufobj, metalbn)) || metalbn == bn)
  178                         break;
  179                 /*
  180                  * If we get here, we've either got the block in the cache
  181                  * or we have a disk address for it, go fetch it.
  182                  */
  183                 if (bp)
  184                         bqrelse(bp);
  185 
  186                 ap->in_exists = 1;
  187                 bp = getblk(vp, metalbn, bsize, 0, 0, 0);
  188                 if ((bp->b_flags & B_CACHE) == 0) {
  189 #ifdef DIAGNOSTIC
  190                         if (!daddr)
  191                                 panic("ufs_bmaparray: indirect block not in cache");
  192 #endif
  193                         bp->b_blkno = blkptrtodb(ump, daddr);
  194                         bp->b_iocmd = BIO_READ;
  195                         bp->b_flags &= ~B_INVAL;
  196                         bp->b_ioflags &= ~BIO_ERROR;
  197                         vfs_busy_pages(bp, 0);
  198                         bp->b_iooffset = dbtob(bp->b_blkno);
  199                         bstrategy(bp);
  200                         curthread->td_ru.ru_inblock++;
  201                         error = bufwait(bp);
  202                         if (error) {
  203                                 brelse(bp);
  204                                 return (error);
  205                         }
  206                 }
  207 
  208                 daddr = ((int32_t *)bp->b_data)[ap->in_off];
  209                 if (num == 1 && daddr && runp) {
  210                         for (bn = ap->in_off + 1;
  211                             bn < MNINDIR(ump) && *runp < maxrun &&
  212                             is_sequential(ump,
  213                             ((int32_t *)bp->b_data)[bn - 1],
  214                             ((int32_t *)bp->b_data)[bn]);
  215                             ++bn, ++*runp);
  216                         bn = ap->in_off;
  217                         if (runb && bn) {
  218                                 for (--bn; bn >= 0 && *runb < maxrun &&
  219                                         is_sequential(ump, ((int32_t *)bp->b_data)[bn],
  220                                             ((int32_t *)bp->b_data)[bn+1]);
  221                                         --bn, ++*runb);
  222                         }
  223                 }
  224         }
  225         if (bp)
  226                 bqrelse(bp);
  227 
  228         /*
  229          * Since this is FFS independent code, we are out of scope for the
  230          * definitions of BLK_NOCOPY and BLK_SNAP, but we do know that they
  231          * will fall in the range 1..um_seqinc, so we use that test and
  232          * return a request for a zeroed out buffer if attempts are made
  233          * to read a BLK_NOCOPY or BLK_SNAP block.
  234          */
  235         if ((ip->i_flags & SF_SNAPSHOT) && daddr > 0 && daddr < ump->um_seqinc){
  236                 *bnp = -1;
  237                 return (0);
  238         }
  239         *bnp = blkptrtodb(ump, daddr);
  240         if (*bnp == 0) {
  241                 *bnp = -1;
  242         }
  243         return (0);
  244 }
  245 
  246 /*
  247  * Create an array of logical block number/offset pairs which represent the
  248  * path of indirect blocks required to access a data block.  The first "pair"
  249  * contains the logical block number of the appropriate single, double or
  250  * triple indirect block and the offset into the inode indirect block array.
  251  * Note, the logical block number of the inode single/double/triple indirect
  252  * block appears twice in the array, once with the offset into the i_ib and
  253  * once with the offset into the page itself.
  254  */
  255 int
  256 ext2_getlbns(vp, bn, ap, nump)
  257         struct vnode *vp;
  258         int32_t bn;
  259         struct indir *ap;
  260         int *nump;
  261 {
  262         long blockcnt, metalbn, realbn;
  263         struct ext2mount *ump;
  264         int i, numlevels, off;
  265         int64_t qblockcnt;
  266 
  267         ump = VFSTOEXT2(vp->v_mount);
  268         if (nump)
  269                 *nump = 0;
  270         numlevels = 0;
  271         realbn = bn;
  272         if ((long)bn < 0)
  273                 bn = -(long)bn;
  274 
  275         /* The first NDADDR blocks are direct blocks. */
  276         if (bn < NDADDR)
  277                 return (0);
  278 
  279         /*
  280          * Determine the number of levels of indirection.  After this loop
  281          * is done, blockcnt indicates the number of data blocks possible
  282          * at the previous level of indirection, and NIADDR - i is the number
  283          * of levels of indirection needed to locate the requested block.
  284          */
  285         for (blockcnt = 1, i = NIADDR, bn -= NDADDR;; i--, bn -= blockcnt) {
  286                 if (i == 0)
  287                         return (EFBIG);
  288                 /*
  289                  * Use int64_t's here to avoid overflow for triple indirect
  290                  * blocks when longs have 32 bits and the block size is more
  291                  * than 4K.
  292                  */
  293                 qblockcnt = (int64_t)blockcnt * MNINDIR(ump);
  294                 if (bn < qblockcnt)
  295                         break;
  296                 blockcnt = qblockcnt;
  297         }
  298 
  299         /* Calculate the address of the first meta-block. */
  300         if (realbn >= 0)
  301                 metalbn = -(realbn - bn + NIADDR - i);
  302         else
  303                 metalbn = -(-realbn - bn + NIADDR - i);
  304 
  305         /*
  306          * At each iteration, off is the offset into the bap array which is
  307          * an array of disk addresses at the current level of indirection.
  308          * The logical block number and the offset in that block are stored
  309          * into the argument array.
  310          */
  311         ap->in_lbn = metalbn;
  312         ap->in_off = off = NIADDR - i;
  313         ap->in_exists = 0;
  314         ap++;
  315         for (++numlevels; i <= NIADDR; i++) {
  316                 /* If searching for a meta-data block, quit when found. */
  317                 if (metalbn == realbn)
  318                         break;
  319 
  320                 off = (bn / blockcnt) % MNINDIR(ump);
  321 
  322                 ++numlevels;
  323                 ap->in_lbn = metalbn;
  324                 ap->in_off = off;
  325                 ap->in_exists = 0;
  326                 ++ap;
  327 
  328                 metalbn -= -1 + off * blockcnt;
  329                 blockcnt /= MNINDIR(ump);
  330         }
  331         if (nump)
  332                 *nump = numlevels;
  333         return (0);
  334 }

Cache object: 8c057245f23444009f921a07712549b3


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