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0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
0004  * Copyright (c) 2013 Red Hat, Inc.
0005  * All Rights Reserved.
0006  */
0007 #include "xfs.h"
0008 #include "xfs_fs.h"
0009 #include "xfs_shared.h"
0010 #include "xfs_format.h"
0011 #include "xfs_log_format.h"
0012 #include "xfs_trans_resv.h"
0013 #include "xfs_bit.h"
0014 #include "xfs_mount.h"
0015 #include "xfs_defer.h"
0016 #include "xfs_da_format.h"
0017 #include "xfs_da_btree.h"
0018 #include "xfs_inode.h"
0019 #include "xfs_trans.h"
0020 #include "xfs_bmap.h"
0021 #include "xfs_attr.h"
0022 #include "xfs_attr_remote.h"
0023 #include "xfs_trace.h"
0024 #include "xfs_error.h"
0025 
0026 #define ATTR_RMTVALUE_MAPSIZE   1   /* # of map entries at once */
0027 
0028 /*
0029  * Remote Attribute Values
0030  * =======================
0031  *
0032  * Remote extended attribute values are conceptually simple -- they're written
0033  * to data blocks mapped by an inode's attribute fork, and they have an upper
0034  * size limit of 64k.  Setting a value does not involve the XFS log.
0035  *
0036  * However, on a v5 filesystem, maximally sized remote attr values require one
0037  * block more than 64k worth of space to hold both the remote attribute value
0038  * header (64 bytes).  On a 4k block filesystem this results in a 68k buffer;
0039  * on a 64k block filesystem, this would be a 128k buffer.  Note that the log
0040  * format can only handle a dirty buffer of XFS_MAX_BLOCKSIZE length (64k).
0041  * Therefore, we /must/ ensure that remote attribute value buffers never touch
0042  * the logging system and therefore never have a log item.
0043  */
0044 
0045 /*
0046  * Each contiguous block has a header, so it is not just a simple attribute
0047  * length to FSB conversion.
0048  */
0049 int
0050 xfs_attr3_rmt_blocks(
0051     struct xfs_mount *mp,
0052     int     attrlen)
0053 {
0054     if (xfs_has_crc(mp)) {
0055         int buflen = XFS_ATTR3_RMT_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
0056         return (attrlen + buflen - 1) / buflen;
0057     }
0058     return XFS_B_TO_FSB(mp, attrlen);
0059 }
0060 
0061 /*
0062  * Checking of the remote attribute header is split into two parts. The verifier
0063  * does CRC, location and bounds checking, the unpacking function checks the
0064  * attribute parameters and owner.
0065  */
0066 static xfs_failaddr_t
0067 xfs_attr3_rmt_hdr_ok(
0068     void            *ptr,
0069     xfs_ino_t       ino,
0070     uint32_t        offset,
0071     uint32_t        size,
0072     xfs_daddr_t     bno)
0073 {
0074     struct xfs_attr3_rmt_hdr *rmt = ptr;
0075 
0076     if (bno != be64_to_cpu(rmt->rm_blkno))
0077         return __this_address;
0078     if (offset != be32_to_cpu(rmt->rm_offset))
0079         return __this_address;
0080     if (size != be32_to_cpu(rmt->rm_bytes))
0081         return __this_address;
0082     if (ino != be64_to_cpu(rmt->rm_owner))
0083         return __this_address;
0084 
0085     /* ok */
0086     return NULL;
0087 }
0088 
0089 static xfs_failaddr_t
0090 xfs_attr3_rmt_verify(
0091     struct xfs_mount    *mp,
0092     struct xfs_buf      *bp,
0093     void            *ptr,
0094     int         fsbsize,
0095     xfs_daddr_t     bno)
0096 {
0097     struct xfs_attr3_rmt_hdr *rmt = ptr;
0098 
0099     if (!xfs_verify_magic(bp, rmt->rm_magic))
0100         return __this_address;
0101     if (!uuid_equal(&rmt->rm_uuid, &mp->m_sb.sb_meta_uuid))
0102         return __this_address;
0103     if (be64_to_cpu(rmt->rm_blkno) != bno)
0104         return __this_address;
0105     if (be32_to_cpu(rmt->rm_bytes) > fsbsize - sizeof(*rmt))
0106         return __this_address;
0107     if (be32_to_cpu(rmt->rm_offset) +
0108                 be32_to_cpu(rmt->rm_bytes) > XFS_XATTR_SIZE_MAX)
0109         return __this_address;
0110     if (rmt->rm_owner == 0)
0111         return __this_address;
0112 
0113     return NULL;
0114 }
0115 
0116 static int
0117 __xfs_attr3_rmt_read_verify(
0118     struct xfs_buf  *bp,
0119     bool        check_crc,
0120     xfs_failaddr_t  *failaddr)
0121 {
0122     struct xfs_mount *mp = bp->b_mount;
0123     char        *ptr;
0124     int     len;
0125     xfs_daddr_t bno;
0126     int     blksize = mp->m_attr_geo->blksize;
0127 
0128     /* no verification of non-crc buffers */
0129     if (!xfs_has_crc(mp))
0130         return 0;
0131 
0132     ptr = bp->b_addr;
0133     bno = xfs_buf_daddr(bp);
0134     len = BBTOB(bp->b_length);
0135     ASSERT(len >= blksize);
0136 
0137     while (len > 0) {
0138         if (check_crc &&
0139             !xfs_verify_cksum(ptr, blksize, XFS_ATTR3_RMT_CRC_OFF)) {
0140             *failaddr = __this_address;
0141             return -EFSBADCRC;
0142         }
0143         *failaddr = xfs_attr3_rmt_verify(mp, bp, ptr, blksize, bno);
0144         if (*failaddr)
0145             return -EFSCORRUPTED;
0146         len -= blksize;
0147         ptr += blksize;
0148         bno += BTOBB(blksize);
0149     }
0150 
0151     if (len != 0) {
0152         *failaddr = __this_address;
0153         return -EFSCORRUPTED;
0154     }
0155 
0156     return 0;
0157 }
0158 
0159 static void
0160 xfs_attr3_rmt_read_verify(
0161     struct xfs_buf  *bp)
0162 {
0163     xfs_failaddr_t  fa;
0164     int     error;
0165 
0166     error = __xfs_attr3_rmt_read_verify(bp, true, &fa);
0167     if (error)
0168         xfs_verifier_error(bp, error, fa);
0169 }
0170 
0171 static xfs_failaddr_t
0172 xfs_attr3_rmt_verify_struct(
0173     struct xfs_buf  *bp)
0174 {
0175     xfs_failaddr_t  fa;
0176     int     error;
0177 
0178     error = __xfs_attr3_rmt_read_verify(bp, false, &fa);
0179     return error ? fa : NULL;
0180 }
0181 
0182 static void
0183 xfs_attr3_rmt_write_verify(
0184     struct xfs_buf  *bp)
0185 {
0186     struct xfs_mount *mp = bp->b_mount;
0187     xfs_failaddr_t  fa;
0188     int     blksize = mp->m_attr_geo->blksize;
0189     char        *ptr;
0190     int     len;
0191     xfs_daddr_t bno;
0192 
0193     /* no verification of non-crc buffers */
0194     if (!xfs_has_crc(mp))
0195         return;
0196 
0197     ptr = bp->b_addr;
0198     bno = xfs_buf_daddr(bp);
0199     len = BBTOB(bp->b_length);
0200     ASSERT(len >= blksize);
0201 
0202     while (len > 0) {
0203         struct xfs_attr3_rmt_hdr *rmt = (struct xfs_attr3_rmt_hdr *)ptr;
0204 
0205         fa = xfs_attr3_rmt_verify(mp, bp, ptr, blksize, bno);
0206         if (fa) {
0207             xfs_verifier_error(bp, -EFSCORRUPTED, fa);
0208             return;
0209         }
0210 
0211         /*
0212          * Ensure we aren't writing bogus LSNs to disk. See
0213          * xfs_attr3_rmt_hdr_set() for the explanation.
0214          */
0215         if (rmt->rm_lsn != cpu_to_be64(NULLCOMMITLSN)) {
0216             xfs_verifier_error(bp, -EFSCORRUPTED, __this_address);
0217             return;
0218         }
0219         xfs_update_cksum(ptr, blksize, XFS_ATTR3_RMT_CRC_OFF);
0220 
0221         len -= blksize;
0222         ptr += blksize;
0223         bno += BTOBB(blksize);
0224     }
0225 
0226     if (len != 0)
0227         xfs_verifier_error(bp, -EFSCORRUPTED, __this_address);
0228 }
0229 
0230 const struct xfs_buf_ops xfs_attr3_rmt_buf_ops = {
0231     .name = "xfs_attr3_rmt",
0232     .magic = { 0, cpu_to_be32(XFS_ATTR3_RMT_MAGIC) },
0233     .verify_read = xfs_attr3_rmt_read_verify,
0234     .verify_write = xfs_attr3_rmt_write_verify,
0235     .verify_struct = xfs_attr3_rmt_verify_struct,
0236 };
0237 
0238 STATIC int
0239 xfs_attr3_rmt_hdr_set(
0240     struct xfs_mount    *mp,
0241     void            *ptr,
0242     xfs_ino_t       ino,
0243     uint32_t        offset,
0244     uint32_t        size,
0245     xfs_daddr_t     bno)
0246 {
0247     struct xfs_attr3_rmt_hdr *rmt = ptr;
0248 
0249     if (!xfs_has_crc(mp))
0250         return 0;
0251 
0252     rmt->rm_magic = cpu_to_be32(XFS_ATTR3_RMT_MAGIC);
0253     rmt->rm_offset = cpu_to_be32(offset);
0254     rmt->rm_bytes = cpu_to_be32(size);
0255     uuid_copy(&rmt->rm_uuid, &mp->m_sb.sb_meta_uuid);
0256     rmt->rm_owner = cpu_to_be64(ino);
0257     rmt->rm_blkno = cpu_to_be64(bno);
0258 
0259     /*
0260      * Remote attribute blocks are written synchronously, so we don't
0261      * have an LSN that we can stamp in them that makes any sense to log
0262      * recovery. To ensure that log recovery handles overwrites of these
0263      * blocks sanely (i.e. once they've been freed and reallocated as some
0264      * other type of metadata) we need to ensure that the LSN has a value
0265      * that tells log recovery to ignore the LSN and overwrite the buffer
0266      * with whatever is in it's log. To do this, we use the magic
0267      * NULLCOMMITLSN to indicate that the LSN is invalid.
0268      */
0269     rmt->rm_lsn = cpu_to_be64(NULLCOMMITLSN);
0270 
0271     return sizeof(struct xfs_attr3_rmt_hdr);
0272 }
0273 
0274 /*
0275  * Helper functions to copy attribute data in and out of the one disk extents
0276  */
0277 STATIC int
0278 xfs_attr_rmtval_copyout(
0279     struct xfs_mount *mp,
0280     struct xfs_buf  *bp,
0281     xfs_ino_t   ino,
0282     int     *offset,
0283     int     *valuelen,
0284     uint8_t     **dst)
0285 {
0286     char        *src = bp->b_addr;
0287     xfs_daddr_t bno = xfs_buf_daddr(bp);
0288     int     len = BBTOB(bp->b_length);
0289     int     blksize = mp->m_attr_geo->blksize;
0290 
0291     ASSERT(len >= blksize);
0292 
0293     while (len > 0 && *valuelen > 0) {
0294         int hdr_size = 0;
0295         int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, blksize);
0296 
0297         byte_cnt = min(*valuelen, byte_cnt);
0298 
0299         if (xfs_has_crc(mp)) {
0300             if (xfs_attr3_rmt_hdr_ok(src, ino, *offset,
0301                           byte_cnt, bno)) {
0302                 xfs_alert(mp,
0303 "remote attribute header mismatch bno/off/len/owner (0x%llx/0x%x/Ox%x/0x%llx)",
0304                     bno, *offset, byte_cnt, ino);
0305                 return -EFSCORRUPTED;
0306             }
0307             hdr_size = sizeof(struct xfs_attr3_rmt_hdr);
0308         }
0309 
0310         memcpy(*dst, src + hdr_size, byte_cnt);
0311 
0312         /* roll buffer forwards */
0313         len -= blksize;
0314         src += blksize;
0315         bno += BTOBB(blksize);
0316 
0317         /* roll attribute data forwards */
0318         *valuelen -= byte_cnt;
0319         *dst += byte_cnt;
0320         *offset += byte_cnt;
0321     }
0322     return 0;
0323 }
0324 
0325 STATIC void
0326 xfs_attr_rmtval_copyin(
0327     struct xfs_mount *mp,
0328     struct xfs_buf  *bp,
0329     xfs_ino_t   ino,
0330     int     *offset,
0331     int     *valuelen,
0332     uint8_t     **src)
0333 {
0334     char        *dst = bp->b_addr;
0335     xfs_daddr_t bno = xfs_buf_daddr(bp);
0336     int     len = BBTOB(bp->b_length);
0337     int     blksize = mp->m_attr_geo->blksize;
0338 
0339     ASSERT(len >= blksize);
0340 
0341     while (len > 0 && *valuelen > 0) {
0342         int hdr_size;
0343         int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, blksize);
0344 
0345         byte_cnt = min(*valuelen, byte_cnt);
0346         hdr_size = xfs_attr3_rmt_hdr_set(mp, dst, ino, *offset,
0347                          byte_cnt, bno);
0348 
0349         memcpy(dst + hdr_size, *src, byte_cnt);
0350 
0351         /*
0352          * If this is the last block, zero the remainder of it.
0353          * Check that we are actually the last block, too.
0354          */
0355         if (byte_cnt + hdr_size < blksize) {
0356             ASSERT(*valuelen - byte_cnt == 0);
0357             ASSERT(len == blksize);
0358             memset(dst + hdr_size + byte_cnt, 0,
0359                     blksize - hdr_size - byte_cnt);
0360         }
0361 
0362         /* roll buffer forwards */
0363         len -= blksize;
0364         dst += blksize;
0365         bno += BTOBB(blksize);
0366 
0367         /* roll attribute data forwards */
0368         *valuelen -= byte_cnt;
0369         *src += byte_cnt;
0370         *offset += byte_cnt;
0371     }
0372 }
0373 
0374 /*
0375  * Read the value associated with an attribute from the out-of-line buffer
0376  * that we stored it in.
0377  *
0378  * Returns 0 on successful retrieval, otherwise an error.
0379  */
0380 int
0381 xfs_attr_rmtval_get(
0382     struct xfs_da_args  *args)
0383 {
0384     struct xfs_bmbt_irec    map[ATTR_RMTVALUE_MAPSIZE];
0385     struct xfs_mount    *mp = args->dp->i_mount;
0386     struct xfs_buf      *bp;
0387     xfs_dablk_t     lblkno = args->rmtblkno;
0388     uint8_t         *dst = args->value;
0389     int         valuelen;
0390     int         nmap;
0391     int         error;
0392     int         blkcnt = args->rmtblkcnt;
0393     int         i;
0394     int         offset = 0;
0395 
0396     trace_xfs_attr_rmtval_get(args);
0397 
0398     ASSERT(args->valuelen != 0);
0399     ASSERT(args->rmtvaluelen == args->valuelen);
0400 
0401     valuelen = args->rmtvaluelen;
0402     while (valuelen > 0) {
0403         nmap = ATTR_RMTVALUE_MAPSIZE;
0404         error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
0405                        blkcnt, map, &nmap,
0406                        XFS_BMAPI_ATTRFORK);
0407         if (error)
0408             return error;
0409         ASSERT(nmap >= 1);
0410 
0411         for (i = 0; (i < nmap) && (valuelen > 0); i++) {
0412             xfs_daddr_t dblkno;
0413             int     dblkcnt;
0414 
0415             ASSERT((map[i].br_startblock != DELAYSTARTBLOCK) &&
0416                    (map[i].br_startblock != HOLESTARTBLOCK));
0417             dblkno = XFS_FSB_TO_DADDR(mp, map[i].br_startblock);
0418             dblkcnt = XFS_FSB_TO_BB(mp, map[i].br_blockcount);
0419             error = xfs_buf_read(mp->m_ddev_targp, dblkno, dblkcnt,
0420                     0, &bp, &xfs_attr3_rmt_buf_ops);
0421             if (error)
0422                 return error;
0423 
0424             error = xfs_attr_rmtval_copyout(mp, bp, args->dp->i_ino,
0425                             &offset, &valuelen,
0426                             &dst);
0427             xfs_buf_relse(bp);
0428             if (error)
0429                 return error;
0430 
0431             /* roll attribute extent map forwards */
0432             lblkno += map[i].br_blockcount;
0433             blkcnt -= map[i].br_blockcount;
0434         }
0435     }
0436     ASSERT(valuelen == 0);
0437     return 0;
0438 }
0439 
0440 /*
0441  * Find a "hole" in the attribute address space large enough for us to drop the
0442  * new attributes value into
0443  */
0444 int
0445 xfs_attr_rmt_find_hole(
0446     struct xfs_da_args  *args)
0447 {
0448     struct xfs_inode    *dp = args->dp;
0449     struct xfs_mount    *mp = dp->i_mount;
0450     int         error;
0451     int         blkcnt;
0452     xfs_fileoff_t       lfileoff = 0;
0453 
0454     /*
0455      * Because CRC enable attributes have headers, we can't just do a
0456      * straight byte to FSB conversion and have to take the header space
0457      * into account.
0458      */
0459     blkcnt = xfs_attr3_rmt_blocks(mp, args->rmtvaluelen);
0460     error = xfs_bmap_first_unused(args->trans, args->dp, blkcnt, &lfileoff,
0461                            XFS_ATTR_FORK);
0462     if (error)
0463         return error;
0464 
0465     args->rmtblkno = (xfs_dablk_t)lfileoff;
0466     args->rmtblkcnt = blkcnt;
0467 
0468     return 0;
0469 }
0470 
0471 int
0472 xfs_attr_rmtval_set_value(
0473     struct xfs_da_args  *args)
0474 {
0475     struct xfs_inode    *dp = args->dp;
0476     struct xfs_mount    *mp = dp->i_mount;
0477     struct xfs_bmbt_irec    map;
0478     xfs_dablk_t     lblkno;
0479     uint8_t         *src = args->value;
0480     int         blkcnt;
0481     int         valuelen;
0482     int         nmap;
0483     int         error;
0484     int         offset = 0;
0485 
0486     /*
0487      * Roll through the "value", copying the attribute value to the
0488      * already-allocated blocks.  Blocks are written synchronously
0489      * so that we can know they are all on disk before we turn off
0490      * the INCOMPLETE flag.
0491      */
0492     lblkno = args->rmtblkno;
0493     blkcnt = args->rmtblkcnt;
0494     valuelen = args->rmtvaluelen;
0495     while (valuelen > 0) {
0496         struct xfs_buf  *bp;
0497         xfs_daddr_t dblkno;
0498         int     dblkcnt;
0499 
0500         ASSERT(blkcnt > 0);
0501 
0502         nmap = 1;
0503         error = xfs_bmapi_read(dp, (xfs_fileoff_t)lblkno,
0504                        blkcnt, &map, &nmap,
0505                        XFS_BMAPI_ATTRFORK);
0506         if (error)
0507             return error;
0508         ASSERT(nmap == 1);
0509         ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
0510                (map.br_startblock != HOLESTARTBLOCK));
0511 
0512         dblkno = XFS_FSB_TO_DADDR(mp, map.br_startblock),
0513         dblkcnt = XFS_FSB_TO_BB(mp, map.br_blockcount);
0514 
0515         error = xfs_buf_get(mp->m_ddev_targp, dblkno, dblkcnt, &bp);
0516         if (error)
0517             return error;
0518         bp->b_ops = &xfs_attr3_rmt_buf_ops;
0519 
0520         xfs_attr_rmtval_copyin(mp, bp, args->dp->i_ino, &offset,
0521                        &valuelen, &src);
0522 
0523         error = xfs_bwrite(bp); /* GROT: NOTE: synchronous write */
0524         xfs_buf_relse(bp);
0525         if (error)
0526             return error;
0527 
0528 
0529         /* roll attribute extent map forwards */
0530         lblkno += map.br_blockcount;
0531         blkcnt -= map.br_blockcount;
0532     }
0533     ASSERT(valuelen == 0);
0534     return 0;
0535 }
0536 
0537 /* Mark stale any incore buffers for the remote value. */
0538 int
0539 xfs_attr_rmtval_stale(
0540     struct xfs_inode    *ip,
0541     struct xfs_bmbt_irec    *map,
0542     xfs_buf_flags_t     incore_flags)
0543 {
0544     struct xfs_mount    *mp = ip->i_mount;
0545     struct xfs_buf      *bp;
0546     int         error;
0547 
0548     ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
0549 
0550     if (XFS_IS_CORRUPT(mp, map->br_startblock == DELAYSTARTBLOCK) ||
0551         XFS_IS_CORRUPT(mp, map->br_startblock == HOLESTARTBLOCK))
0552         return -EFSCORRUPTED;
0553 
0554     error = xfs_buf_incore(mp->m_ddev_targp,
0555             XFS_FSB_TO_DADDR(mp, map->br_startblock),
0556             XFS_FSB_TO_BB(mp, map->br_blockcount),
0557             incore_flags, &bp);
0558     if (error) {
0559         if (error == -ENOENT)
0560             return 0;
0561         return error;
0562     }
0563 
0564     xfs_buf_stale(bp);
0565     xfs_buf_relse(bp);
0566     return 0;
0567 }
0568 
0569 /*
0570  * Find a hole for the attr and store it in the delayed attr context.  This
0571  * initializes the context to roll through allocating an attr extent for a
0572  * delayed attr operation
0573  */
0574 int
0575 xfs_attr_rmtval_find_space(
0576     struct xfs_attr_intent      *attr)
0577 {
0578     struct xfs_da_args      *args = attr->xattri_da_args;
0579     struct xfs_bmbt_irec        *map = &attr->xattri_map;
0580     int             error;
0581 
0582     attr->xattri_lblkno = 0;
0583     attr->xattri_blkcnt = 0;
0584     args->rmtblkcnt = 0;
0585     args->rmtblkno = 0;
0586     memset(map, 0, sizeof(struct xfs_bmbt_irec));
0587 
0588     error = xfs_attr_rmt_find_hole(args);
0589     if (error)
0590         return error;
0591 
0592     attr->xattri_blkcnt = args->rmtblkcnt;
0593     attr->xattri_lblkno = args->rmtblkno;
0594 
0595     return 0;
0596 }
0597 
0598 /*
0599  * Write one block of the value associated with an attribute into the
0600  * out-of-line buffer that we have defined for it. This is similar to a subset
0601  * of xfs_attr_rmtval_set, but records the current block to the delayed attr
0602  * context, and leaves transaction handling to the caller.
0603  */
0604 int
0605 xfs_attr_rmtval_set_blk(
0606     struct xfs_attr_intent      *attr)
0607 {
0608     struct xfs_da_args      *args = attr->xattri_da_args;
0609     struct xfs_inode        *dp = args->dp;
0610     struct xfs_bmbt_irec        *map = &attr->xattri_map;
0611     int nmap;
0612     int error;
0613 
0614     nmap = 1;
0615     error = xfs_bmapi_write(args->trans, dp,
0616             (xfs_fileoff_t)attr->xattri_lblkno,
0617             attr->xattri_blkcnt, XFS_BMAPI_ATTRFORK, args->total,
0618             map, &nmap);
0619     if (error)
0620         return error;
0621 
0622     ASSERT(nmap == 1);
0623     ASSERT((map->br_startblock != DELAYSTARTBLOCK) &&
0624            (map->br_startblock != HOLESTARTBLOCK));
0625 
0626     /* roll attribute extent map forwards */
0627     attr->xattri_lblkno += map->br_blockcount;
0628     attr->xattri_blkcnt -= map->br_blockcount;
0629 
0630     return 0;
0631 }
0632 
0633 /*
0634  * Remove the value associated with an attribute by deleting the
0635  * out-of-line buffer that it is stored on.
0636  */
0637 int
0638 xfs_attr_rmtval_invalidate(
0639     struct xfs_da_args  *args)
0640 {
0641     xfs_dablk_t     lblkno;
0642     int         blkcnt;
0643     int         error;
0644 
0645     /*
0646      * Roll through the "value", invalidating the attribute value's blocks.
0647      */
0648     lblkno = args->rmtblkno;
0649     blkcnt = args->rmtblkcnt;
0650     while (blkcnt > 0) {
0651         struct xfs_bmbt_irec    map;
0652         int         nmap;
0653 
0654         /*
0655          * Try to remember where we decided to put the value.
0656          */
0657         nmap = 1;
0658         error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
0659                        blkcnt, &map, &nmap, XFS_BMAPI_ATTRFORK);
0660         if (error)
0661             return error;
0662         if (XFS_IS_CORRUPT(args->dp->i_mount, nmap != 1))
0663             return -EFSCORRUPTED;
0664         error = xfs_attr_rmtval_stale(args->dp, &map, XBF_TRYLOCK);
0665         if (error)
0666             return error;
0667 
0668         lblkno += map.br_blockcount;
0669         blkcnt -= map.br_blockcount;
0670     }
0671     return 0;
0672 }
0673 
0674 /*
0675  * Remove the value associated with an attribute by deleting the out-of-line
0676  * buffer that it is stored on. Returns -EAGAIN for the caller to refresh the
0677  * transaction and re-call the function.  Callers should keep calling this
0678  * routine until it returns something other than -EAGAIN.
0679  */
0680 int
0681 xfs_attr_rmtval_remove(
0682     struct xfs_attr_intent      *attr)
0683 {
0684     struct xfs_da_args      *args = attr->xattri_da_args;
0685     int             error, done;
0686 
0687     /*
0688      * Unmap value blocks for this attr.
0689      */
0690     error = xfs_bunmapi(args->trans, args->dp, args->rmtblkno,
0691                 args->rmtblkcnt, XFS_BMAPI_ATTRFORK, 1, &done);
0692     if (error)
0693         return error;
0694 
0695     /*
0696      * We don't need an explicit state here to pick up where we left off. We
0697      * can figure it out using the !done return code. The actual value of
0698      * attr->xattri_dela_state may be some value reminiscent of the calling
0699      * function, but it's value is irrelevant with in the context of this
0700      * function. Once we are done here, the next state is set as needed by
0701      * the parent
0702      */
0703     if (!done) {
0704         trace_xfs_attr_rmtval_remove_return(attr->xattri_dela_state,
0705                             args->dp);
0706         return -EAGAIN;
0707     }
0708 
0709     args->rmtblkno = 0;
0710     args->rmtblkcnt = 0;
0711     return 0;
0712 }
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