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  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1989, 1991, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  * (c) UNIX System Laboratories, Inc.
    7  * All or some portions of this file are derived from material licensed
    8  * to the University of California by American Telephone and Telegraph
    9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   10  * the permission of UNIX System Laboratories, Inc.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  *      @(#)ufs_bmap.c  8.7 (Berkeley) 3/21/95
   37  * $FreeBSD: releng/12.0/sys/fs/ext2fs/ext2_bmap.c 333584 2018-05-13 19:19:10Z fsu $
   38  */
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/bio.h>
   43 #include <sys/buf.h>
   44 #include <sys/proc.h>
   45 #include <sys/vnode.h>
   46 #include <sys/mount.h>
   47 #include <sys/racct.h>
   48 #include <sys/resourcevar.h>
   49 #include <sys/stat.h>
   50 
   51 #include <fs/ext2fs/fs.h>
   52 #include <fs/ext2fs/inode.h>
   53 #include <fs/ext2fs/ext2fs.h>
   54 #include <fs/ext2fs/ext2_dinode.h>
   55 #include <fs/ext2fs/ext2_extern.h>
   56 #include <fs/ext2fs/ext2_mount.h>
   57 
   58 /*
   59  * Bmap converts the logical block number of a file to its physical block
   60  * number on the disk. The conversion is done by using the logical block
   61  * number to index into the array of block pointers described by the dinode.
   62  */
   63 int
   64 ext2_bmap(struct vop_bmap_args *ap)
   65 {
   66         daddr_t blkno;
   67         int error;
   68 
   69         /*
   70          * Check for underlying vnode requests and ensure that logical
   71          * to physical mapping is requested.
   72          */
   73         if (ap->a_bop != NULL)
   74                 *ap->a_bop = &VTOI(ap->a_vp)->i_devvp->v_bufobj;
   75         if (ap->a_bnp == NULL)
   76                 return (0);
   77 
   78         if (VTOI(ap->a_vp)->i_flag & IN_E4EXTENTS)
   79                 error = ext4_bmapext(ap->a_vp, ap->a_bn, &blkno,
   80                     ap->a_runp, ap->a_runb);
   81         else
   82                 error = ext2_bmaparray(ap->a_vp, ap->a_bn, &blkno,
   83                     ap->a_runp, ap->a_runb);
   84         *ap->a_bnp = blkno;
   85         return (error);
   86 }
   87 
   88 /*
   89  * Convert the logical block number of a file to its physical block number
   90  * on the disk within ext4 extents.
   91  */
   92 int
   93 ext4_bmapext(struct vnode *vp, int32_t bn, int64_t *bnp, int *runp, int *runb)
   94 {
   95         struct inode *ip;
   96         struct m_ext2fs *fs;
   97         struct ext4_extent_header *ehp;
   98         struct ext4_extent *ep;
   99         struct ext4_extent_path *path = NULL;
  100         daddr_t lbn;
  101         int error, depth;
  102 
  103         ip = VTOI(vp);
  104         fs = ip->i_e2fs;
  105         lbn = bn;
  106         ehp = (struct ext4_extent_header *)ip->i_data;
  107         depth = ehp->eh_depth;
  108 
  109         *bnp = -1;
  110         if (runp != NULL)
  111                 *runp = 0;
  112         if (runb != NULL)
  113                 *runb = 0;
  114 
  115         error = ext4_ext_find_extent(ip, lbn, &path);
  116         if (error)
  117                 return (error);
  118 
  119         ep = path[depth].ep_ext;
  120         if(ep) {
  121                 if (lbn < ep->e_blk) {
  122                         if (runp != NULL)
  123                                 *runp = ep->e_blk - lbn - 1;
  124                 } else if (ep->e_blk <= lbn && lbn < ep->e_blk + ep->e_len) {
  125                         *bnp = fsbtodb(fs, lbn - ep->e_blk +
  126                             (ep->e_start_lo | (daddr_t)ep->e_start_hi << 32));
  127                         if (runp != NULL)
  128                                 *runp = ep->e_len - (lbn - ep->e_blk) - 1;
  129                         if (runb != NULL)
  130                                 *runb = lbn - ep->e_blk;
  131                 } else {
  132                         if (runb != NULL)
  133                                 *runb = ep->e_blk + lbn - ep->e_len;
  134                 }
  135         }
  136 
  137         ext4_ext_path_free(path);
  138 
  139         return (error);
  140 }
  141 
  142 /*
  143  * Indirect blocks are now on the vnode for the file.  They are given negative
  144  * logical block numbers.  Indirect blocks are addressed by the negative
  145  * address of the first data block to which they point.  Double indirect blocks
  146  * are addressed by one less than the address of the first indirect block to
  147  * which they point.  Triple indirect blocks are addressed by one less than
  148  * the address of the first double indirect block to which they point.
  149  *
  150  * ext2_bmaparray does the bmap conversion, and if requested returns the
  151  * array of logical blocks which must be traversed to get to a block.
  152  * Each entry contains the offset into that block that gets you to the
  153  * next block and the disk address of the block (if it is assigned).
  154  */
  155 
  156 int
  157 ext2_bmaparray(struct vnode *vp, daddr_t bn, daddr_t *bnp, int *runp, int *runb)
  158 {
  159         struct inode *ip;
  160         struct buf *bp;
  161         struct ext2mount *ump;
  162         struct mount *mp;
  163         struct indir a[EXT2_NIADDR + 1], *ap;
  164         daddr_t daddr;
  165         e2fs_lbn_t metalbn;
  166         int error, num, maxrun = 0, bsize;
  167         int *nump;
  168 
  169         ap = NULL;
  170         ip = VTOI(vp);
  171         mp = vp->v_mount;
  172         ump = VFSTOEXT2(mp);
  173 
  174         bsize = EXT2_BLOCK_SIZE(ump->um_e2fs);
  175 
  176         if (runp) {
  177                 maxrun = mp->mnt_iosize_max / bsize - 1;
  178                 *runp = 0;
  179         }
  180         if (runb)
  181                 *runb = 0;
  182 
  183 
  184         ap = a;
  185         nump = &num;
  186         error = ext2_getlbns(vp, bn, ap, nump);
  187         if (error)
  188                 return (error);
  189 
  190         num = *nump;
  191         if (num == 0) {
  192                 *bnp = blkptrtodb(ump, ip->i_db[bn]);
  193                 if (*bnp == 0) {
  194                         *bnp = -1;
  195                 } else if (runp) {
  196                         daddr_t bnb = bn;
  197 
  198                         for (++bn; bn < EXT2_NDADDR && *runp < maxrun &&
  199                             is_sequential(ump, ip->i_db[bn - 1], ip->i_db[bn]);
  200                             ++bn, ++*runp);
  201                         bn = bnb;
  202                         if (runb && (bn > 0)) {
  203                                 for (--bn; (bn >= 0) && (*runb < maxrun) &&
  204                                         is_sequential(ump, ip->i_db[bn],
  205                                                 ip->i_db[bn + 1]);
  206                                                 --bn, ++*runb);
  207                         }
  208                 }
  209                 return (0);
  210         }
  211 
  212         /* Get disk address out of indirect block array */
  213         daddr = ip->i_ib[ap->in_off];
  214 
  215         for (bp = NULL, ++ap; --num; ++ap) {
  216                 /*
  217                  * Exit the loop if there is no disk address assigned yet and
  218                  * the indirect block isn't in the cache, or if we were
  219                  * looking for an indirect block and we've found it.
  220                  */
  221 
  222                 metalbn = ap->in_lbn;
  223                 if ((daddr == 0 && !incore(&vp->v_bufobj, metalbn)) || metalbn == bn)
  224                         break;
  225                 /*
  226                  * If we get here, we've either got the block in the cache
  227                  * or we have a disk address for it, go fetch it.
  228                  */
  229                 if (bp)
  230                         bqrelse(bp);
  231 
  232                 bp = getblk(vp, metalbn, bsize, 0, 0, 0);
  233                 if ((bp->b_flags & B_CACHE) == 0) {
  234 #ifdef INVARIANTS
  235                         if (!daddr)
  236                                 panic("ext2_bmaparray: indirect block not in cache");
  237 #endif
  238                         bp->b_blkno = blkptrtodb(ump, daddr);
  239                         bp->b_iocmd = BIO_READ;
  240                         bp->b_flags &= ~B_INVAL;
  241                         bp->b_ioflags &= ~BIO_ERROR;
  242                         vfs_busy_pages(bp, 0);
  243                         bp->b_iooffset = dbtob(bp->b_blkno);
  244                         bstrategy(bp);
  245 #ifdef RACCT
  246                         if (racct_enable) {
  247                                 PROC_LOCK(curproc);
  248                                 racct_add_buf(curproc, bp, 0);
  249                                 PROC_UNLOCK(curproc);
  250                         }
  251 #endif
  252                         curthread->td_ru.ru_inblock++;
  253                         error = bufwait(bp);
  254                         if (error) {
  255                                 brelse(bp);
  256                                 return (error);
  257                         }
  258                 }
  259 
  260                 daddr = ((e2fs_daddr_t *)bp->b_data)[ap->in_off];
  261                 if (num == 1 && daddr && runp) {
  262                         for (bn = ap->in_off + 1;
  263                             bn < MNINDIR(ump) && *runp < maxrun &&
  264                             is_sequential(ump,
  265                             ((e2fs_daddr_t *)bp->b_data)[bn - 1],
  266                             ((e2fs_daddr_t *)bp->b_data)[bn]);
  267                             ++bn, ++*runp);
  268                         bn = ap->in_off;
  269                         if (runb && bn) {
  270                                 for (--bn; bn >= 0 && *runb < maxrun &&
  271                                         is_sequential(ump,
  272                                         ((e2fs_daddr_t *)bp->b_data)[bn],
  273                                         ((e2fs_daddr_t *)bp->b_data)[bn + 1]);
  274                                         --bn, ++*runb);
  275                         }
  276                 }
  277         }
  278         if (bp)
  279                 bqrelse(bp);
  280 
  281         /*
  282          * Since this is FFS independent code, we are out of scope for the
  283          * definitions of BLK_NOCOPY and BLK_SNAP, but we do know that they
  284          * will fall in the range 1..um_seqinc, so we use that test and
  285          * return a request for a zeroed out buffer if attempts are made
  286          * to read a BLK_NOCOPY or BLK_SNAP block.
  287          */
  288         if ((ip->i_flags & SF_SNAPSHOT) && daddr > 0 && daddr < ump->um_seqinc) {
  289                 *bnp = -1;
  290                 return (0);
  291         }
  292         *bnp = blkptrtodb(ump, daddr);
  293         if (*bnp == 0) {
  294                 *bnp = -1;
  295         }
  296         return (0);
  297 }
  298 
  299 /*
  300  * Create an array of logical block number/offset pairs which represent the
  301  * path of indirect blocks required to access a data block.  The first "pair"
  302  * contains the logical block number of the appropriate single, double or
  303  * triple indirect block and the offset into the inode indirect block array.
  304  * Note, the logical block number of the inode single/double/triple indirect
  305  * block appears twice in the array, once with the offset into the i_ib and
  306  * once with the offset into the page itself.
  307  */
  308 int
  309 ext2_getlbns(struct vnode *vp, daddr_t bn, struct indir *ap, int *nump)
  310 {
  311         long blockcnt;
  312         e2fs_lbn_t metalbn, realbn;
  313         struct ext2mount *ump;
  314         int i, numlevels, off;
  315         int64_t qblockcnt;
  316 
  317         ump = VFSTOEXT2(vp->v_mount);
  318         if (nump)
  319                 *nump = 0;
  320         numlevels = 0;
  321         realbn = bn;
  322         if ((long)bn < 0)
  323                 bn = -(long)bn;
  324 
  325         /* The first EXT2_NDADDR blocks are direct blocks. */
  326         if (bn < EXT2_NDADDR)
  327                 return (0);
  328 
  329         /*
  330          * Determine the number of levels of indirection.  After this loop
  331          * is done, blockcnt indicates the number of data blocks possible
  332          * at the previous level of indirection, and EXT2_NIADDR - i is the
  333          * number of levels of indirection needed to locate the requested block.
  334          */
  335         for (blockcnt = 1, i = EXT2_NIADDR, bn -= EXT2_NDADDR; ;
  336             i--, bn -= blockcnt) {
  337                 if (i == 0)
  338                         return (EFBIG);
  339                 /*
  340                  * Use int64_t's here to avoid overflow for triple indirect
  341                  * blocks when longs have 32 bits and the block size is more
  342                  * than 4K.
  343                  */
  344                 qblockcnt = (int64_t)blockcnt * MNINDIR(ump);
  345                 if (bn < qblockcnt)
  346                         break;
  347                 blockcnt = qblockcnt;
  348         }
  349 
  350         /* Calculate the address of the first meta-block. */
  351         if (realbn >= 0)
  352                 metalbn = -(realbn - bn + EXT2_NIADDR - i);
  353         else
  354                 metalbn = -(-realbn - bn + EXT2_NIADDR - i);
  355 
  356         /*
  357          * At each iteration, off is the offset into the bap array which is
  358          * an array of disk addresses at the current level of indirection.
  359          * The logical block number and the offset in that block are stored
  360          * into the argument array.
  361          */
  362         ap->in_lbn = metalbn;
  363         ap->in_off = off = EXT2_NIADDR - i;
  364         ap++;
  365         for (++numlevels; i <= EXT2_NIADDR; i++) {
  366                 /* If searching for a meta-data block, quit when found. */
  367                 if (metalbn == realbn)
  368                         break;
  369 
  370                 off = (bn / blockcnt) % MNINDIR(ump);
  371 
  372                 ++numlevels;
  373                 ap->in_lbn = metalbn;
  374                 ap->in_off = off;
  375                 ++ap;
  376 
  377                 metalbn -= -1 + off * blockcnt;
  378                 blockcnt /= MNINDIR(ump);
  379         }
  380         if (nump)
  381                 *nump = numlevels;
  382         return (0);
  383 }

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