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

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 1989, 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      * (c) UNIX System Laboratories, Inc.
      * All or some portions of this file are derived from material licensed
      * to the University of California by American Telephone and Telegraph
      * Co. or Unix System Laboratories, Inc. and are reproduced herein with
     * the permission of UNIX System Laboratories, Inc.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)ufs_bmap.c  8.7 (Berkeley) 3/21/95
     * $FreeBSD$
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bio.h>
    #include <sys/buf.h>
    #include <sys/endian.h>
    #include <sys/proc.h>
    #include <sys/vnode.h>
    #include <sys/mount.h>
    #include <sys/racct.h>
    #include <sys/resourcevar.h>
    #include <sys/stat.h>
    
    #include <fs/ext2fs/fs.h>
    #include <fs/ext2fs/inode.h>
    #include <fs/ext2fs/ext2fs.h>
    #include <fs/ext2fs/ext2_dinode.h>
    #include <fs/ext2fs/ext2_extern.h>
    #include <fs/ext2fs/ext2_mount.h>
    
    /*
     * Bmap converts the logical block number of a file to its physical block
     * number on the disk. The conversion is done by using the logical block
     * number to index into the array of block pointers described by the dinode.
     */
    int
    ext2_bmap(struct vop_bmap_args *ap)
    {
            daddr_t blkno;
            int error;
    
            /*
             * Check for underlying vnode requests and ensure that logical
             * to physical mapping is requested.
             */
            if (ap->a_bop != NULL)
                    *ap->a_bop = &VTOI(ap->a_vp)->i_devvp->v_bufobj;
            if (ap->a_bnp == NULL)
                    return (0);
    
            if (VTOI(ap->a_vp)->i_flag & IN_E4EXTENTS)
                    error = ext4_bmapext(ap->a_vp, ap->a_bn, &blkno,
                        ap->a_runp, ap->a_runb);
            else
                    error = ext2_bmaparray(ap->a_vp, ap->a_bn, &blkno,
                        ap->a_runp, ap->a_runb);
            *ap->a_bnp = blkno;
            return (error);
    }
    
    /*
     * Convert the logical block number of a file to its physical block number
     * on the disk within ext4 extents.
     */
    int
    ext4_bmapext(struct vnode *vp, int32_t bn, int64_t *bnp, int *runp, int *runb)
    {
            struct inode *ip;
            struct m_ext2fs *fs;
            struct mount *mp;
            struct ext2mount *ump;
           struct ext4_extent_header *ehp;
           struct ext4_extent *ep;
           struct ext4_extent_path *path = NULL;
           daddr_t lbn;
           int error, depth, maxrun = 0, bsize;
   
           ip = VTOI(vp);
           fs = ip->i_e2fs;
           mp = vp->v_mount;
           ump = VFSTOEXT2(mp);
           lbn = bn;
           ehp = (struct ext4_extent_header *)ip->i_data;
           depth = le16toh(ehp->eh_depth);
           bsize = EXT2_BLOCK_SIZE(ump->um_e2fs);
   
           *bnp = -1;
           if (runp != NULL) {
                   maxrun = mp->mnt_iosize_max / bsize - 1;
                   *runp = 0;
           }
           if (runb != NULL)
                   *runb = 0;
   
           error = ext4_ext_find_extent(ip, lbn, &path);
           if (error)
                   return (error);
   
           ep = path[depth].ep_ext;
           if(ep) {
                   if (lbn < le32toh(ep->e_blk)) {
                           if (runp != NULL) {
                                   *runp = min(maxrun, le32toh(ep->e_blk) - lbn - 1);
                           }
                   } else if (le32toh(ep->e_blk) <= lbn &&
                               lbn < le32toh(ep->e_blk) + le16toh(ep->e_len)) {
                           *bnp = fsbtodb(fs, lbn - le32toh(ep->e_blk) +
                               (le32toh(ep->e_start_lo) |
                               (daddr_t)le16toh(ep->e_start_hi) << 32));
                           if (runp != NULL) {
                                   *runp = min(maxrun,
                                       le16toh(ep->e_len) -
                                       (lbn - le32toh(ep->e_blk)) - 1);
                           }
                           if (runb != NULL)
                                   *runb = min(maxrun, lbn - le32toh(ep->e_blk));
                   } else {
                           if (runb != NULL)
                                   *runb = min(maxrun, le32toh(ep->e_blk) + lbn -
                                       le16toh(ep->e_len));
                   }
           }
   
           ext4_ext_path_free(path);
   
           return (error);
   }
   
   static int
   readindir(struct vnode *vp, e2fs_lbn_t lbn, e2fs_daddr_t daddr, struct buf **bpp)
   {
           struct buf *bp;
           struct mount *mp;
           struct ext2mount *ump;
           int error;
   
           mp = vp->v_mount;
           ump = VFSTOEXT2(mp);
   
           bp = getblk(vp, lbn, mp->mnt_stat.f_iosize, 0, 0, 0);
           if ((bp->b_flags & B_CACHE) == 0) {
                   KASSERT(daddr != 0,
                       ("readindir: indirect block not in cache"));
   
                   bp->b_blkno = blkptrtodb(ump, daddr);
                   bp->b_iocmd = BIO_READ;
                   bp->b_flags &= ~B_INVAL;
                   bp->b_ioflags &= ~BIO_ERROR;
                   vfs_busy_pages(bp, 0);
                   bp->b_iooffset = dbtob(bp->b_blkno);
                   bstrategy(bp);
   #ifdef RACCT
                   if (racct_enable) {
                           PROC_LOCK(curproc);
                           racct_add_buf(curproc, bp, 0);
                           PROC_UNLOCK(curproc);
                   }
   #endif
                   curthread->td_ru.ru_inblock++;
                   error = bufwait(bp);
                   if (error != 0) {
                           brelse(bp);
                           return (error);
                   }
           }
           *bpp = bp;
           return (0);
   }
   
   /*
    * Indirect blocks are now on the vnode for the file.  They are given negative
    * logical block numbers.  Indirect blocks are addressed by the negative
    * address of the first data block to which they point.  Double indirect blocks
    * are addressed by one less than the address of the first indirect block to
    * which they point.  Triple indirect blocks are addressed by one less than
    * the address of the first double indirect block to which they point.
    *
    * ext2_bmaparray does the bmap conversion, and if requested returns the
    * array of logical blocks which must be traversed to get to a block.
    * Each entry contains the offset into that block that gets you to the
    * next block and the disk address of the block (if it is assigned).
    */
   
   int
   ext2_bmaparray(struct vnode *vp, daddr_t bn, daddr_t *bnp, int *runp, int *runb)
   {
           struct inode *ip;
           struct buf *bp;
           struct ext2mount *ump;
           struct mount *mp;
           struct indir a[EXT2_NIADDR + 1], *ap;
           daddr_t daddr;
           e2fs_lbn_t metalbn;
           int error, num, maxrun = 0, bsize;
           int *nump;
   
           ap = NULL;
           ip = VTOI(vp);
           mp = vp->v_mount;
           ump = VFSTOEXT2(mp);
   
           bsize = EXT2_BLOCK_SIZE(ump->um_e2fs);
   
           if (runp) {
                   maxrun = mp->mnt_iosize_max / bsize - 1;
                   *runp = 0;
           }
           if (runb)
                   *runb = 0;
   
           ap = a;
           nump = &num;
           error = ext2_getlbns(vp, bn, ap, nump);
           if (error)
                   return (error);
   
           num = *nump;
           if (num == 0) {
                   *bnp = blkptrtodb(ump, ip->i_db[bn]);
                   if (*bnp == 0) {
                           *bnp = -1;
                   } else if (runp) {
                           daddr_t bnb = bn;
   
                           for (++bn; bn < EXT2_NDADDR && *runp < maxrun &&
                               is_sequential(ump, ip->i_db[bn - 1], ip->i_db[bn]);
                               ++bn, ++*runp);
                           bn = bnb;
                           if (runb && (bn > 0)) {
                                   for (--bn; (bn >= 0) && (*runb < maxrun) &&
                                           is_sequential(ump, ip->i_db[bn],
                                                   ip->i_db[bn + 1]);
                                                   --bn, ++*runb);
                           }
                   }
                   return (0);
           }
   
           /* Get disk address out of indirect block array */
           daddr = ip->i_ib[ap->in_off];
   
           for (bp = NULL, ++ap; --num; ++ap) {
                   /*
                    * Exit the loop if there is no disk address assigned yet and
                    * the indirect block isn't in the cache, or if we were
                    * looking for an indirect block and we've found it.
                    */
   
                   metalbn = ap->in_lbn;
                   if ((daddr == 0 && !incore(&vp->v_bufobj, metalbn)) || metalbn == bn)
                           break;
                   /*
                    * If we get here, we've either got the block in the cache
                    * or we have a disk address for it, go fetch it.
                    */
                   if (bp)
                           bqrelse(bp);
                   error = readindir(vp, metalbn, daddr, &bp);
                   if (error != 0)
                           return (error);
   
                   daddr = le32toh(((e2fs_daddr_t *)bp->b_data)[ap->in_off]);
                   if (num == 1 && daddr && runp) {
                           for (bn = ap->in_off + 1;
                               bn < MNINDIR(ump) && *runp < maxrun &&
                               is_sequential(ump,
                               ((e2fs_daddr_t *)bp->b_data)[bn - 1],
                               ((e2fs_daddr_t *)bp->b_data)[bn]);
                               ++bn, ++*runp);
                           bn = ap->in_off;
                           if (runb && bn) {
                                   for (--bn; bn >= 0 && *runb < maxrun &&
                                           is_sequential(ump,
                                           ((e2fs_daddr_t *)bp->b_data)[bn],
                                           ((e2fs_daddr_t *)bp->b_data)[bn + 1]);
                                           --bn, ++*runb);
                           }
                   }
           }
           if (bp)
                   bqrelse(bp);
   
           /*
            * Since this is FFS independent code, we are out of scope for the
            * definitions of BLK_NOCOPY and BLK_SNAP, but we do know that they
            * will fall in the range 1..um_seqinc, so we use that test and
            * return a request for a zeroed out buffer if attempts are made
            * to read a BLK_NOCOPY or BLK_SNAP block.
            */
           if ((ip->i_flags & SF_SNAPSHOT) && daddr > 0 && daddr < ump->um_seqinc) {
                   *bnp = -1;
                   return (0);
           }
           *bnp = blkptrtodb(ump, daddr);
           if (*bnp == 0) {
                   *bnp = -1;
           }
           return (0);
   }
   
   static e2fs_lbn_t
   lbn_count(struct ext2mount *ump, int level)
   
   {
           e2fs_lbn_t blockcnt;
   
           for (blockcnt = 1; level > 0; level--)
                   blockcnt *= MNINDIR(ump);
           return (blockcnt);
   }
   
   int
   ext2_bmap_seekdata(struct vnode *vp, off_t *offp)
   {
           struct buf *bp;
           struct indir a[EXT2_NIADDR + 1], *ap;
           struct inode *ip;
           struct mount *mp;
           struct ext2mount *ump;
           e2fs_daddr_t bn, daddr, nextbn;
           uint64_t bsize;
           off_t numblks;
           int error, num, num1, off;
   
           bp = NULL;
           error = 0;
           ip = VTOI(vp);
           mp = vp->v_mount;
           ump = VFSTOEXT2(mp);
   
           if (vp->v_type != VREG || (ip->i_flags & SF_SNAPSHOT) != 0)
                   return (EINVAL);
           if (*offp < 0 || *offp >= ip->i_size)
                   return (ENXIO);
   
           bsize = mp->mnt_stat.f_iosize;
           for (bn = *offp / bsize, numblks = howmany(ip->i_size, bsize);
               bn < numblks; bn = nextbn) {
                   if (bn < EXT2_NDADDR) {
                           daddr = ip->i_db[bn];
                           if (daddr != 0)
                                   break;
                           nextbn = bn + 1;
                           continue;
                   }
   
                   ap = a;
                   error = ext2_getlbns(vp, bn, ap, &num);
                   if (error != 0)
                           break;
                   MPASS(num >= 2);
                   daddr = ip->i_ib[ap->in_off];
                   ap++, num--;
                   for (nextbn = EXT2_NDADDR, num1 = num - 1; num1 > 0; num1--)
                           nextbn += lbn_count(ump, num1);
                   if (daddr == 0) {
                           nextbn += lbn_count(ump, num);
                           continue;
                   }
   
                   for (; daddr != 0 && num > 0; ap++, num--) {
                           if (bp != NULL)
                                   bqrelse(bp);
                           error = readindir(vp, ap->in_lbn, daddr, &bp);
                           if (error != 0)
                                   return (error);
   
                           /*
                            * Scan the indirect block until we find a non-zero
                            * pointer.
                            */
                           off = ap->in_off;
                           do {
                                   daddr = le32toh(((e2fs_daddr_t *)bp->b_data)[off]);
                           } while (daddr == 0 && ++off < MNINDIR(ump));
                           nextbn += off * lbn_count(ump, num - 1);
   
                           /*
                            * We need to recompute the LBNs of indirect
                            * blocks, so restart with the updated block offset.
                            */
                           if (off != ap->in_off)
                                   break;
                   }
                   if (num == 0) {
                           /*
                            * We found a data block.
                            */
                           bn = nextbn;
                           break;
                   }
           }
           if (bp != NULL)
                   bqrelse(bp);
           if (bn >= numblks)
                   error = ENXIO;
           if (error == 0 && *offp < bn * bsize)
                   *offp = bn * bsize;
           return (error);
   }
   
   /*
    * Create an array of logical block number/offset pairs which represent the
    * path of indirect blocks required to access a data block.  The first "pair"
    * contains the logical block number of the appropriate single, double or
    * triple indirect block and the offset into the inode indirect block array.
    * Note, the logical block number of the inode single/double/triple indirect
    * block appears twice in the array, once with the offset into the i_ib and
    * once with the offset into the page itself.
    */
   int
   ext2_getlbns(struct vnode *vp, daddr_t bn, struct indir *ap, int *nump)
   {
           long blockcnt;
           e2fs_lbn_t metalbn, realbn;
           struct ext2mount *ump;
           int i, numlevels, off;
           int64_t qblockcnt;
   
           ump = VFSTOEXT2(vp->v_mount);
           if (nump)
                   *nump = 0;
           numlevels = 0;
           realbn = bn;
           if ((long)bn < 0)
                   bn = -(long)bn;
   
           /* The first EXT2_NDADDR blocks are direct blocks. */
           if (bn < EXT2_NDADDR)
                   return (0);
   
           /*
            * Determine the number of levels of indirection.  After this loop
            * is done, blockcnt indicates the number of data blocks possible
            * at the previous level of indirection, and EXT2_NIADDR - i is the
            * number of levels of indirection needed to locate the requested block.
            */
           for (blockcnt = 1, i = EXT2_NIADDR, bn -= EXT2_NDADDR; ;
               i--, bn -= blockcnt) {
                   if (i == 0)
                           return (EFBIG);
                   /*
                    * Use int64_t's here to avoid overflow for triple indirect
                    * blocks when longs have 32 bits and the block size is more
                    * than 4K.
                    */
                   qblockcnt = (int64_t)blockcnt * MNINDIR(ump);
                   if (bn < qblockcnt)
                           break;
                   blockcnt = qblockcnt;
           }
   
           /* Calculate the address of the first meta-block. */
           if (realbn >= 0)
                   metalbn = -(realbn - bn + EXT2_NIADDR - i);
           else
                   metalbn = -(-realbn - bn + EXT2_NIADDR - i);
   
           /*
            * At each iteration, off is the offset into the bap array which is
            * an array of disk addresses at the current level of indirection.
            * The logical block number and the offset in that block are stored
            * into the argument array.
            */
           ap->in_lbn = metalbn;
           ap->in_off = off = EXT2_NIADDR - i;
           ap++;
           for (++numlevels; i <= EXT2_NIADDR; i++) {
                   /* If searching for a meta-data block, quit when found. */
                   if (metalbn == realbn)
                           break;
   
                   off = (bn / blockcnt) % MNINDIR(ump);
   
                   ++numlevels;
                   ap->in_lbn = metalbn;
                   ap->in_off = off;
                   ++ap;
   
                   metalbn -= -1 + off * blockcnt;
                   blockcnt /= MNINDIR(ump);
           }
           if (nump)
                   *nump = numlevels;
           return (0);
   }

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