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authorChris Mason <clm@fb.com>2015-09-19 11:28:25 -0700
committerChris Mason <clm@fb.com>2016-06-03 12:32:34 -0700
commit8dff9c85341032767d7b519217a79ea04cd676b0 (patch)
treefb6fada259a38e9eb68660b4f0e3376714b890d4
parentf881dd29bf31fb9e8072a3a47c834fa804f7d249 (diff)
downloadlinux-8dff9c85341032767d7b519217a79ea04cd676b0.tar.gz
Btrfs: deal with duplciates during extent_map insertion in btrfs_get_extent
When dealing with inline extents, btrfs_get_extent will incorrectly try to insert a duplicate extent_map. The dup hits -EEXIST from add_extent_map, but then we try to merge with the existing one and end up trying to insert a zero length extent_map. This actually works most of the time, except when there are extent maps past the end of the inline extent. rocksdb will trigger this sometimes because it preallocates an extent and then truncates down. Josef made a script to trigger with xfs_io: #!/bin/bash xfs_io -f -c "pwrite 0 1000" inline xfs_io -c "falloc -k 4k 1M" inline xfs_io -c "pread 0 1000" -c "fadvise -d 0 1000" -c "pread 0 1000" inline xfs_io -c "fadvise -d 0 1000" inline cat inline You'll get EIOs trying to read inline after this because add_extent_map is returning EEXIST Signed-off-by: Chris Mason <clm@fb.com>
-rw-r--r--fs/btrfs/inode.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 2debd42c4660..e5558d9e396e 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6979,7 +6979,18 @@ insert:
* existing will always be non-NULL, since there must be
* extent causing the -EEXIST.
*/
- if (start >= extent_map_end(existing) ||
+ if (existing->start == em->start &&
+ extent_map_end(existing) == extent_map_end(em) &&
+ em->block_start == existing->block_start) {
+ /*
+ * these two extents are the same, it happens
+ * with inlines especially
+ */
+ free_extent_map(em);
+ em = existing;
+ err = 0;
+
+ } else if (start >= extent_map_end(existing) ||
start <= existing->start) {
/*
* The existing extent map is the one nearest to