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authorJosef Bacik <josef@redhat.com>2012-05-31 11:06:33 -0400
committerChris Mason <chris.mason@oracle.com>2012-06-14 21:29:11 -0400
commitb939d1ab76b4aa816343cdbd8b44ce9929a3b9ef (patch)
tree231ff204d260f0d50b8789029937750d7d4f8952
parentbeb42dd793193a3d4e72970bfa73cd8810f63cea (diff)
downloadlinux-b939d1ab76b4aa816343cdbd8b44ce9929a3b9ef.tar.bz2
Btrfs: fix locking in btrfs_destroy_delayed_refs
The transaction abort stuff was throwing warnings from the list debugging code because we do a list_del_init outside of the delayed_refs spin lock. The delayed refs locking makes baby Jesus cry so it's not hard to get wrong, but we need to take the ref head mutex to make sure it's not being processed currently, and so if it is we need to drop the spin lock and then take and drop the mutex and do the search again. If we can take the mutex then we can safely remove the head from the list and carry on. Now when the transaction aborts I don't get the list debugging warnings. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com>
-rw-r--r--fs/btrfs/disk-io.c30
1 files changed, 17 insertions, 13 deletions
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b99d5127ba18..c79ddc756081 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3400,7 +3400,6 @@ int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
delayed_refs = &trans->delayed_refs;
-again:
spin_lock(&delayed_refs->lock);
if (delayed_refs->num_entries == 0) {
spin_unlock(&delayed_refs->lock);
@@ -3408,31 +3407,36 @@ again:
return ret;
}
- node = rb_first(&delayed_refs->root);
- while (node) {
+ while ((node = rb_first(&delayed_refs->root)) != NULL) {
ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
- node = rb_next(node);
-
- ref->in_tree = 0;
- rb_erase(&ref->rb_node, &delayed_refs->root);
- delayed_refs->num_entries--;
atomic_set(&ref->refs, 1);
if (btrfs_delayed_ref_is_head(ref)) {
struct btrfs_delayed_ref_head *head;
head = btrfs_delayed_node_to_head(ref);
- spin_unlock(&delayed_refs->lock);
- mutex_lock(&head->mutex);
+ if (!mutex_trylock(&head->mutex)) {
+ atomic_inc(&ref->refs);
+ spin_unlock(&delayed_refs->lock);
+
+ /* Need to wait for the delayed ref to run */
+ mutex_lock(&head->mutex);
+ mutex_unlock(&head->mutex);
+ btrfs_put_delayed_ref(ref);
+
+ continue;
+ }
+
kfree(head->extent_op);
delayed_refs->num_heads--;
if (list_empty(&head->cluster))
delayed_refs->num_heads_ready--;
list_del_init(&head->cluster);
- mutex_unlock(&head->mutex);
- btrfs_put_delayed_ref(ref);
- goto again;
}
+ ref->in_tree = 0;
+ rb_erase(&ref->rb_node, &delayed_refs->root);
+ delayed_refs->num_entries--;
+
spin_unlock(&delayed_refs->lock);
btrfs_put_delayed_ref(ref);