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  * $FreeBSD$
   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 mount *mp;
   98         struct ext2mount *ump;
   99         struct ext4_extent_header *ehp;
  100         struct ext4_extent *ep;
  101         struct ext4_extent_path *path = NULL;
  102         daddr_t lbn;
  103         int error, depth, maxrun = 0, bsize;
  104 
  105         ip = VTOI(vp);
  106         fs = ip->i_e2fs;
  107         mp = vp->v_mount;
  108         ump = VFSTOEXT2(mp);
  109         lbn = bn;
  110         ehp = (struct ext4_extent_header *)ip->i_data;
  111         depth = ehp->eh_depth;
  112         bsize = EXT2_BLOCK_SIZE(ump->um_e2fs);
  113 
  114         *bnp = -1;
  115         if (runp != NULL) {
  116                 maxrun = mp->mnt_iosize_max / bsize - 1;
  117                 *runp = 0;
  118         }
  119         if (runb != NULL)
  120                 *runb = 0;
  121 
  122         error = ext4_ext_find_extent(ip, lbn, &path);
  123         if (error)
  124                 return (error);
  125 
  126         ep = path[depth].ep_ext;
  127         if(ep) {
  128                 if (lbn < ep->e_blk) {
  129                         if (runp != NULL) {
  130                                 *runp = min(maxrun, ep->e_blk - lbn - 1);
  131                         }
  132                 } else if (ep->e_blk <= lbn && lbn < ep->e_blk + ep->e_len) {
  133                         *bnp = fsbtodb(fs, lbn - ep->e_blk +
  134                             (ep->e_start_lo | (daddr_t)ep->e_start_hi << 32));
  135                         if (runp != NULL) {
  136                                 *runp = min(maxrun,
  137                                     ep->e_len - (lbn - ep->e_blk) - 1);
  138                         }
  139                         if (runb != NULL)
  140                                 *runb = min(maxrun, lbn - ep->e_blk);
  141                 } else {
  142                         if (runb != NULL)
  143                                 *runb = min(maxrun, ep->e_blk + lbn - ep->e_len);
  144                 }
  145         }
  146 
  147         ext4_ext_path_free(path);
  148 
  149         return (error);
  150 }
  151 
  152 static int
  153 readindir(struct vnode *vp, e2fs_lbn_t lbn, e2fs_daddr_t daddr, struct buf **bpp)
  154 {
  155         struct buf *bp;
  156         struct mount *mp;
  157         struct ext2mount *ump;
  158         int error;
  159 
  160         mp = vp->v_mount;
  161         ump = VFSTOEXT2(mp);
  162 
  163         bp = getblk(vp, lbn, mp->mnt_stat.f_iosize, 0, 0, 0);
  164         if ((bp->b_flags & B_CACHE) == 0) {
  165                 KASSERT(daddr != 0,
  166                     ("readindir: indirect block not in cache"));
  167 
  168                 bp->b_blkno = blkptrtodb(ump, daddr);
  169                 bp->b_iocmd = BIO_READ;
  170                 bp->b_flags &= ~B_INVAL;
  171                 bp->b_ioflags &= ~BIO_ERROR;
  172                 vfs_busy_pages(bp, 0);
  173                 bp->b_iooffset = dbtob(bp->b_blkno);
  174                 bstrategy(bp);
  175 #ifdef RACCT
  176                 if (racct_enable) {
  177                         PROC_LOCK(curproc);
  178                         racct_add_buf(curproc, bp, 0);
  179                         PROC_UNLOCK(curproc);
  180                 }
  181 #endif
  182                 curthread->td_ru.ru_inblock++;
  183                 error = bufwait(bp);
  184                 if (error != 0) {
  185                         brelse(bp);
  186                         return (error);
  187                 }
  188         }
  189         *bpp = bp;
  190         return (0);
  191 }
  192 
  193 /*
  194  * Indirect blocks are now on the vnode for the file.  They are given negative
  195  * logical block numbers.  Indirect blocks are addressed by the negative
  196  * address of the first data block to which they point.  Double indirect blocks
  197  * are addressed by one less than the address of the first indirect block to
  198  * which they point.  Triple indirect blocks are addressed by one less than
  199  * the address of the first double indirect block to which they point.
  200  *
  201  * ext2_bmaparray does the bmap conversion, and if requested returns the
  202  * array of logical blocks which must be traversed to get to a block.
  203  * Each entry contains the offset into that block that gets you to the
  204  * next block and the disk address of the block (if it is assigned).
  205  */
  206 
  207 int
  208 ext2_bmaparray(struct vnode *vp, daddr_t bn, daddr_t *bnp, int *runp, int *runb)
  209 {
  210         struct inode *ip;
  211         struct buf *bp;
  212         struct ext2mount *ump;
  213         struct mount *mp;
  214         struct indir a[EXT2_NIADDR + 1], *ap;
  215         daddr_t daddr;
  216         e2fs_lbn_t metalbn;
  217         int error, num, maxrun = 0, bsize;
  218         int *nump;
  219 
  220         ap = NULL;
  221         ip = VTOI(vp);
  222         mp = vp->v_mount;
  223         ump = VFSTOEXT2(mp);
  224 
  225         bsize = EXT2_BLOCK_SIZE(ump->um_e2fs);
  226 
  227         if (runp) {
  228                 maxrun = mp->mnt_iosize_max / bsize - 1;
  229                 *runp = 0;
  230         }
  231         if (runb)
  232                 *runb = 0;
  233 
  234 
  235         ap = a;
  236         nump = &num;
  237         error = ext2_getlbns(vp, bn, ap, nump);
  238         if (error)
  239                 return (error);
  240 
  241         num = *nump;
  242         if (num == 0) {
  243                 *bnp = blkptrtodb(ump, ip->i_db[bn]);
  244                 if (*bnp == 0) {
  245                         *bnp = -1;
  246                 } else if (runp) {
  247                         daddr_t bnb = bn;
  248 
  249                         for (++bn; bn < EXT2_NDADDR && *runp < maxrun &&
  250                             is_sequential(ump, ip->i_db[bn - 1], ip->i_db[bn]);
  251                             ++bn, ++*runp);
  252                         bn = bnb;
  253                         if (runb && (bn > 0)) {
  254                                 for (--bn; (bn >= 0) && (*runb < maxrun) &&
  255                                         is_sequential(ump, ip->i_db[bn],
  256                                                 ip->i_db[bn + 1]);
  257                                                 --bn, ++*runb);
  258                         }
  259                 }
  260                 return (0);
  261         }
  262 
  263         /* Get disk address out of indirect block array */
  264         daddr = ip->i_ib[ap->in_off];
  265 
  266         for (bp = NULL, ++ap; --num; ++ap) {
  267                 /*
  268                  * Exit the loop if there is no disk address assigned yet and
  269                  * the indirect block isn't in the cache, or if we were
  270                  * looking for an indirect block and we've found it.
  271                  */
  272 
  273                 metalbn = ap->in_lbn;
  274                 if ((daddr == 0 && !incore(&vp->v_bufobj, metalbn)) || metalbn == bn)
  275                         break;
  276                 /*
  277                  * If we get here, we've either got the block in the cache
  278                  * or we have a disk address for it, go fetch it.
  279                  */
  280                 if (bp)
  281                         bqrelse(bp);
  282                 error = readindir(vp, metalbn, daddr, &bp);
  283                 if (error != 0)
  284                         return (error);
  285 
  286                 daddr = ((e2fs_daddr_t *)bp->b_data)[ap->in_off];
  287                 if (num == 1 && daddr && runp) {
  288                         for (bn = ap->in_off + 1;
  289                             bn < MNINDIR(ump) && *runp < maxrun &&
  290                             is_sequential(ump,
  291                             ((e2fs_daddr_t *)bp->b_data)[bn - 1],
  292                             ((e2fs_daddr_t *)bp->b_data)[bn]);
  293                             ++bn, ++*runp);
  294                         bn = ap->in_off;
  295                         if (runb && bn) {
  296                                 for (--bn; bn >= 0 && *runb < maxrun &&
  297                                         is_sequential(ump,
  298                                         ((e2fs_daddr_t *)bp->b_data)[bn],
  299                                         ((e2fs_daddr_t *)bp->b_data)[bn + 1]);
  300                                         --bn, ++*runb);
  301                         }
  302                 }
  303         }
  304         if (bp)
  305                 bqrelse(bp);
  306 
  307         /*
  308          * Since this is FFS independent code, we are out of scope for the
  309          * definitions of BLK_NOCOPY and BLK_SNAP, but we do know that they
  310          * will fall in the range 1..um_seqinc, so we use that test and
  311          * return a request for a zeroed out buffer if attempts are made
  312          * to read a BLK_NOCOPY or BLK_SNAP block.
  313          */
  314         if ((ip->i_flags & SF_SNAPSHOT) && daddr > 0 && daddr < ump->um_seqinc) {
  315                 *bnp = -1;
  316                 return (0);
  317         }
  318         *bnp = blkptrtodb(ump, daddr);
  319         if (*bnp == 0) {
  320                 *bnp = -1;
  321         }
  322         return (0);
  323 }
  324 
  325 static e2fs_lbn_t
  326 lbn_count(struct ext2mount *ump, int level)
  327 
  328 {
  329         e2fs_lbn_t blockcnt;
  330 
  331         for (blockcnt = 1; level > 0; level--)
  332                 blockcnt *= MNINDIR(ump);
  333         return (blockcnt);
  334 }
  335 
  336 int
  337 ext2_bmap_seekdata(struct vnode *vp, off_t *offp)
  338 {
  339         struct buf *bp;
  340         struct indir a[EXT2_NIADDR + 1], *ap;
  341         struct inode *ip;
  342         struct mount *mp;
  343         struct ext2mount *ump;
  344         e2fs_daddr_t bn, daddr, nextbn;
  345         uint64_t bsize;
  346         off_t numblks;
  347         int error, num, num1, off;
  348 
  349         bp = NULL;
  350         error = 0;
  351         ip = VTOI(vp);
  352         mp = vp->v_mount;
  353         ump = VFSTOEXT2(mp);
  354 
  355         if (vp->v_type != VREG || (ip->i_flags & SF_SNAPSHOT) != 0)
  356                 return (EINVAL);
  357         if (*offp < 0 || *offp >= ip->i_size)
  358                 return (ENXIO);
  359 
  360         bsize = mp->mnt_stat.f_iosize;
  361         for (bn = *offp / bsize, numblks = howmany(ip->i_size, bsize);
  362             bn < numblks; bn = nextbn) {
  363                 if (bn < EXT2_NDADDR) {
  364                         daddr = ip->i_db[bn];
  365                         if (daddr != 0)
  366                                 break;
  367                         nextbn = bn + 1;
  368                         continue;
  369                 }
  370 
  371                 ap = a;
  372                 error = ext2_getlbns(vp, bn, ap, &num);
  373                 if (error != 0)
  374                         break;
  375                 MPASS(num >= 2);
  376                 daddr = ip->i_ib[ap->in_off];
  377                 ap++, num--;
  378                 for (nextbn = EXT2_NDADDR, num1 = num - 1; num1 > 0; num1--)
  379                         nextbn += lbn_count(ump, num1);
  380                 if (daddr == 0) {
  381                         nextbn += lbn_count(ump, num);
  382                         continue;
  383                 }
  384 
  385                 for (; daddr != 0 && num > 0; ap++, num--) {
  386                         if (bp != NULL)
  387                                 bqrelse(bp);
  388                         error = readindir(vp, ap->in_lbn, daddr, &bp);
  389                         if (error != 0)
  390                                 return (error);
  391 
  392                         /*
  393                          * Scan the indirect block until we find a non-zero
  394                          * pointer.
  395                          */
  396                         off = ap->in_off;
  397                         do {
  398                                 daddr = ((e2fs_daddr_t *)bp->b_data)[off];
  399                         } while (daddr == 0 && ++off < MNINDIR(ump));
  400                         nextbn += off * lbn_count(ump, num - 1);
  401 
  402                         /*
  403                          * We need to recompute the LBNs of indirect
  404                          * blocks, so restart with the updated block offset.
  405                          */
  406                         if (off != ap->in_off)
  407                                 break;
  408                 }
  409                 if (num == 0) {
  410                         /*
  411                          * We found a data block.
  412                          */
  413                         bn = nextbn;
  414                         break;
  415                 }
  416         }
  417         if (bp != NULL)
  418                 bqrelse(bp);
  419         if (bn >= numblks)
  420                 error = ENXIO;
  421         if (error == 0 && *offp < bn * bsize)
  422                 *offp = bn * bsize;
  423         return (error);
  424 }
  425 
  426 /*
  427  * Create an array of logical block number/offset pairs which represent the
  428  * path of indirect blocks required to access a data block.  The first "pair"
  429  * contains the logical block number of the appropriate single, double or
  430  * triple indirect block and the offset into the inode indirect block array.
  431  * Note, the logical block number of the inode single/double/triple indirect
  432  * block appears twice in the array, once with the offset into the i_ib and
  433  * once with the offset into the page itself.
  434  */
  435 int
  436 ext2_getlbns(struct vnode *vp, daddr_t bn, struct indir *ap, int *nump)
  437 {
  438         long blockcnt;
  439         e2fs_lbn_t metalbn, realbn;
  440         struct ext2mount *ump;
  441         int i, numlevels, off;
  442         int64_t qblockcnt;
  443 
  444         ump = VFSTOEXT2(vp->v_mount);
  445         if (nump)
  446                 *nump = 0;
  447         numlevels = 0;
  448         realbn = bn;
  449         if ((long)bn < 0)
  450                 bn = -(long)bn;
  451 
  452         /* The first EXT2_NDADDR blocks are direct blocks. */
  453         if (bn < EXT2_NDADDR)
  454                 return (0);
  455 
  456         /*
  457          * Determine the number of levels of indirection.  After this loop
  458          * is done, blockcnt indicates the number of data blocks possible
  459          * at the previous level of indirection, and EXT2_NIADDR - i is the
  460          * number of levels of indirection needed to locate the requested block.
  461          */
  462         for (blockcnt = 1, i = EXT2_NIADDR, bn -= EXT2_NDADDR; ;
  463             i--, bn -= blockcnt) {
  464                 if (i == 0)
  465                         return (EFBIG);
  466                 /*
  467                  * Use int64_t's here to avoid overflow for triple indirect
  468                  * blocks when longs have 32 bits and the block size is more
  469                  * than 4K.
  470                  */
  471                 qblockcnt = (int64_t)blockcnt * MNINDIR(ump);
  472                 if (bn < qblockcnt)
  473                         break;
  474                 blockcnt = qblockcnt;
  475         }
  476 
  477         /* Calculate the address of the first meta-block. */
  478         if (realbn >= 0)
  479                 metalbn = -(realbn - bn + EXT2_NIADDR - i);
  480         else
  481                 metalbn = -(-realbn - bn + EXT2_NIADDR - i);
  482 
  483         /*
  484          * At each iteration, off is the offset into the bap array which is
  485          * an array of disk addresses at the current level of indirection.
  486          * The logical block number and the offset in that block are stored
  487          * into the argument array.
  488          */
  489         ap->in_lbn = metalbn;
  490         ap->in_off = off = EXT2_NIADDR - i;
  491         ap++;
  492         for (++numlevels; i <= EXT2_NIADDR; i++) {
  493                 /* If searching for a meta-data block, quit when found. */
  494                 if (metalbn == realbn)
  495                         break;
  496 
  497                 off = (bn / blockcnt) % MNINDIR(ump);
  498 
  499                 ++numlevels;
  500                 ap->in_lbn = metalbn;
  501                 ap->in_off = off;
  502                 ++ap;
  503 
  504                 metalbn -= -1 + off * blockcnt;
  505                 blockcnt /= MNINDIR(ump);
  506         }
  507         if (nump)
  508                 *nump = numlevels;
  509         return (0);
  510 }

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