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authorJosef Bacik <josef@redhat.com>2011-06-08 14:45:50 -0400
committerArne Jansen <sensille@gmx.net>2011-06-10 12:14:12 +0200
commitad3e34bba4b64ab8e1f5ea1a17768e1a0d9648ea (patch)
tree46f2081646866cea4f89d8f20c5f632f14e3bc2a /fs/btrfs
parentaa0467d8d2a00e75b2bb6a56a4ee6d70c5d1928f (diff)
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>
Diffstat (limited to 'fs/btrfs')
-rw-r--r--fs/btrfs/ctree.c10
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;
}