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authorChris Mason <chris.mason@oracle.com>2009-07-31 14:57:55 -0400
committerChris Mason <chris.mason@oracle.com>2009-07-31 14:57:55 -0400
commit013f1b12f4fc479f697acae2f31bad220162cd03 (patch)
treeb51225aa32f249de352840b31b49eb9799fdafe8
parent6606bb97e146a387932efee263745b7240a11193 (diff)
Btrfs: make sure the async caching thread advances the key
The async caching thread can end up looping forever if a given search puts it at the last key in a leaf. It will end up calling btrfs_next_leaf and then checking if it needs to politely drop the read semaphore. Most of the time this looping isn't noticed because it is able to make progress the next time around. But, during log replay, we wait on the async caching thread to finish, and the async thread is waiting on the commit, and no progress is really made. The fix used here is to copy the key out of the next leaf, that way our search lands there properly. Signed-off-by: Chris Mason <chris.mason@oracle.com>
-rw-r--r--fs/btrfs/extent-tree.c21
1 files changed, 17 insertions, 4 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index dc84daee6bc..72a2b9c28e9 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -265,10 +265,6 @@ static int caching_kthread(void *data)
atomic_inc(&block_group->space_info->caching_threads);
last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
-again:
- /* need to make sure the commit_root doesn't disappear */
- down_read(&fs_info->extent_commit_sem);
-
/*
* We don't want to deadlock with somebody trying to allocate a new
* extent for the extent root while also trying to search the extent
@@ -282,6 +278,10 @@ again:
key.objectid = last;
key.offset = 0;
btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
+again:
+ /* need to make sure the commit_root doesn't disappear */
+ down_read(&fs_info->extent_commit_sem);
+
ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
if (ret < 0)
goto err;
@@ -304,6 +304,19 @@ again:
if (need_resched() ||
btrfs_transaction_in_commit(fs_info)) {
+ leaf = path->nodes[0];
+
+ /* this shouldn't happen, but if the
+ * leaf is empty just move on.
+ */
+ if (btrfs_header_nritems(leaf) == 0)
+ break;
+ /*
+ * we need to copy the key out so that
+ * we are sure the next search advances
+ * us forward in the btree.
+ */
+ btrfs_item_key_to_cpu(leaf, &key, 0);
btrfs_release_path(fs_info->extent_root, path);
up_read(&fs_info->extent_commit_sem);
schedule_timeout(1);