Josef Bacik
2011-Jun-08 18:45 UTC
[PATCH] 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>
---
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 d840893..2e66786 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;
}
--
1.7.5.2
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Arne Jansen
2011-Jun-09 06:55 UTC
Re: [PATCH] Btrfs: don''t map extent buffer if path->skip_locking is set
On 08.06.2011 20:45, Josef Bacik wrote:> 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>This fixes the BUGs I saw, so you can add a Tested-by: Arne Jansen <sensille@gmx.net> if you like. -Arne> --- > 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 d840893..2e66786 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; > }-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html