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From time to time people report space map corruption resulting in panic

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(ss == NULL) on pool import. I had such a panic recently. With current version
of ZFS it is still possible to import the pool in readonly mode and backup
all the data, but in case it is impossible for some reason add tunable
vfs.zfs.space_map_last_hope, which when set to '1' will tell ZFS to remove
colliding range and retry. This seems to have worked for me, but I consider
it highly risky to use.

MFC after:	1 week
This commit is contained in:
pjd 2011-12-18 12:27:45 +00:00
parent 3c1d6d1593
commit 952e2f20b5
1 changed files with 25 additions and 1 deletions
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26
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/space_map.c
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@ -29,6 +29,13 @@
#include <sys/zio.h>
#include <sys/space_map.h>
SYSCTL_DECL(_vfs_zfs);
static int space_map_last_hope;
TUNABLE_INT("vfs.zfs.space_map_last_hope", &space_map_last_hope);
SYSCTL_INT(_vfs_zfs, OID_AUTO, space_map_last_hope, CTLFLAG_RDTUN,
&space_map_last_hope, 0,
"If kernel panic in space_map code on pool import, import the pool in readonly mode and backup all your data before trying this option.");
/*
* Space map routines.
* NOTE: caller is responsible for all locking.
@ -93,7 +100,7 @@ space_map_add(space_map_t *sm, uint64_t start, uint64_t size)
VERIFY(sm->sm_space + size <= sm->sm_size);
VERIFY(P2PHASE(start, 1ULL << sm->sm_shift) == 0);
VERIFY(P2PHASE(size, 1ULL << sm->sm_shift) == 0);
again:
ssearch.ss_start = start;
ssearch.ss_end = end;
ss = avl_find(&sm->sm_root, &ssearch, &where);
@ -104,6 +111,23 @@ space_map_add(space_map_t *sm, uint64_t start, uint64_t size)
(longlong_t)start, (longlong_t)size);
return;
}
if (ss != NULL && space_map_last_hope) {
uint64_t sstart, ssize;
if (ss->ss_start > start)
sstart = ss->ss_start;
else
sstart = start;
if (ss->ss_end > end)
ssize = end - sstart;
else
ssize = ss->ss_end - sstart;
ZFS_LOG(0,
"Removing colliding space_map range (start=%ju end=%ju). Good luck!",
(uintmax_t)sstart, (uintmax_t)(sstart + ssize));
space_map_remove(sm, sstart, ssize);
goto again;
}
/* Make sure we don't overlap with either of our neighbors */
VERIFY(ss == NULL);