svn commit: r228686 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Pawel Jakub Dawidek]

Author: pjd
Date: Sun Dec 18 12:27:45 2011
New Revision: 228686
URL: http://svn.freebsd.org/changeset/base/228686

Log:
  From time to time people report space map corruption resulting in panic
  (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

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/space_map.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/space_map.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/space_map.c	Sun Dec 18 12:19:03 2011	(r228685)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/space_map.c	Sun Dec 18 12:27:45 2011	(r228686)
@@ -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 
 	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 
 		    (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);