diff options
| author | Josef Bacik <josef@redhat.com> | 2011-06-08 14:36:54 -0400 |
|---|---|---|
| committer | Josef Bacik <josef@redhat.com> | 2011-06-09 10:12:07 -0400 |
| commit | 25b8b936ed44814a5ce6fc3b2a21401f33cd56f6 (patch) | |
| tree | 3f95ff0f54340bf63885e1d38766cf52a05d3029 | |
| parent | f6a398298d34af66ec3a2d82a44a4dbc5277357d (diff) | |
| download | lwn-25b8b936ed44814a5ce6fc3b2a21401f33cd56f6.tar.gz lwn-25b8b936ed44814a5ce6fc3b2a21401f33cd56f6.zip | |
Btrfs: don't map extent buffer if path->skip_locking is set
Arne's scrub stuff exposed a problem with mapping the extent buffer in
reada_for_search. He searches the commit root with multiple threads and with
skip_locking set, so we can race and overwrite node->map_token since node isn't
locked. So fix this so that we only map the extent buffer if we don't already
have a map_token and skip_locking isn't set. Without this patch scrub would
panic almost immediately, with the patch it doesn't panic anymore. Thanks,
Reported-by: Arne Jansen <sensille@gmx.net>
Signed-off-by: Josef Bacik <josef@redhat.com>
| -rw-r--r-- | fs/btrfs/ctree.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index d84089349c82..2e667868e0d2 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -1228,6 +1228,7 @@ static void reada_for_search(struct btrfs_root *root, u32 nr; u32 blocksize; u32 nscan = 0; + bool map = true; if (level != 1) return; @@ -1249,8 +1250,11 @@ static void reada_for_search(struct btrfs_root *root, nritems = btrfs_header_nritems(node); nr = slot; + if (node->map_token || path->skip_locking) + map = false; + while (1) { - if (!node->map_token) { + if (map && !node->map_token) { unsigned long offset = btrfs_node_key_ptr_offset(nr); map_private_extent_buffer(node, offset, sizeof(struct btrfs_key_ptr), @@ -1277,7 +1281,7 @@ static void reada_for_search(struct btrfs_root *root, if ((search <= target && target - search <= 65536) || (search > target && search - target <= 65536)) { gen = btrfs_node_ptr_generation(node, nr); - if (node->map_token) { + if (map && node->map_token) { unmap_extent_buffer(node, node->map_token, KM_USER1); node->map_token = NULL; @@ -1289,7 +1293,7 @@ static void reada_for_search(struct btrfs_root *root, if ((nread > 65536 || nscan > 32)) break; } - if (node->map_token) { + if (map && node->map_token) { unmap_extent_buffer(node, node->map_token, KM_USER1); node->map_token = NULL; } |