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MFV 316905

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7740 fix for 6513 only works in hole punching case, not truncation

illumos/illumos-gate@7de35a3ed0
7de35a3ed0

https://www.illumos.org/issues/7740
  The problem is that dbuf_findbp will return ENOENT if the block it's
  trying to find is beyond the end of the file. If that happens, we assume
  there is no birth time, and so we lose that information when we write
  out new blkptrs. We should teach dbuf_findbp to look for things that are
  beyond the current end, but not beyond the absolute end of the file.
  To verify, create a large file, truncate it to a short length, and then
  write beyond the end. Check with zdb to make sure that there are no
  holes with birth time zero (will appear as gaps).

Reviewed by: Steve Gonczi <steve.gonczi@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Paul Dagnelie <pcd@delphix.com>
This commit is contained in:
Josh Paetzel 2017-04-28 02:11:29 +00:00
commit 285d85ab04
2 changed files with 33 additions and 9 deletions
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36
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c
View File

@ -2161,8 +2161,6 @@ static int
dbuf_findbp(dnode_t *dn, int level, uint64_t blkid, int fail_sparse,
dmu_buf_impl_t **parentp, blkptr_t **bpp)
{
int nlevels, epbs;
*parentp = NULL;
*bpp = NULL;
@ -2181,17 +2179,35 @@ dbuf_findbp(dnode_t *dn, int level, uint64_t blkid, int fail_sparse,
return (0);
}
if (dn->dn_phys->dn_nlevels == 0)
nlevels = 1;
else
nlevels = dn->dn_phys->dn_nlevels;
epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
int nlevels =
(dn->dn_phys->dn_nlevels == 0) ? 1 : dn->dn_phys->dn_nlevels;
int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
ASSERT3U(level * epbs, <, 64);
ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
/*
* This assertion shouldn't trip as long as the max indirect block size
* is less than 1M. The reason for this is that up to that point,
* the number of levels required to address an entire object with blocks
* of size SPA_MINBLOCKSIZE satisfies nlevels * epbs + 1 <= 64. In
* other words, if N * epbs + 1 > 64, then if (N-1) * epbs + 1 > 55
* (i.e. we can address the entire object), objects will all use at most
* N-1 levels and the assertion won't overflow. However, once epbs is
* 13, 4 * 13 + 1 = 53, but 5 * 13 + 1 = 66. Then, 4 levels will not be
* enough to address an entire object, so objects will have 5 levels,
* but then this assertion will overflow.
*
* All this is to say that if we ever increase DN_MAX_INDBLKSHIFT, we
* need to redo this logic to handle overflows.
*/
ASSERT(level >= nlevels ||
((nlevels - level - 1) * epbs) +
highbit64(dn->dn_phys->dn_nblkptr) <= 64);
if (level >= nlevels ||
(blkid > (dn->dn_phys->dn_maxblkid >> (level * epbs)))) {
blkid >= ((uint64_t)dn->dn_phys->dn_nblkptr <<
((nlevels - level - 1) * epbs)) ||
(fail_sparse &&
blkid > (dn->dn_phys->dn_maxblkid >> (level * epbs)))) {
/* the buffer has no parent yet */
return (SET_ERROR(ENOENT));
} else if (level < nlevels-1) {
@ -2209,6 +2225,8 @@ dbuf_findbp(dnode_t *dn, int level, uint64_t blkid, int fail_sparse,
}
*bpp = ((blkptr_t *)(*parentp)->db.db_data) +
(blkid & ((1ULL << epbs) - 1));
if (blkid > (dn->dn_phys->dn_maxblkid >> (level * epbs)))
ASSERT(BP_IS_HOLE(*bpp));
return (0);
} else {
/* the block is referenced from the dnode */

6
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dnode.h
View File

@ -58,6 +58,12 @@ extern "C" {
*/
#define DNODE_SHIFT 9 /* 512 bytes */
#define DN_MIN_INDBLKSHIFT 12 /* 4k */
/*
* If we ever increase this value beyond 20, we need to revisit all logic that
* does x << level * ebps to handle overflow. With a 1M indirect block size,
* 4 levels of indirect blocks would not be able to guarantee addressing an
* entire object, so 5 levels will be used, but 5 * (20 - 7) = 65.
*/
#define DN_MAX_INDBLKSHIFT 17 /* 128k */
#define DNODE_BLOCK_SHIFT 14 /* 16k */
#define DNODE_CORE_SIZE 64 /* 64 bytes for dnode sans blkptrs */