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authorOmar Sandoval <osandov@fb.com>2016-05-20 13:50:33 -0700
committerChris Mason <clm@fb.com>2016-06-25 06:20:10 -0700
commit02dbfc99b424dde3cf0a492ed3bec4f222441754 (patch)
treed08f267bac15ea5939185424bbe73306b7f11cb6 /fs/btrfs/delayed-inode.c
parent33688abb2802ff3a230bd2441f765477b94cc89e (diff)
Btrfs: fix ->iterate_shared() by upgrading i_rwsem for delayed nodes
Commit fe742fd4f90f ("Revert "btrfs: switch to ->iterate_shared()"") backed out the conversion to ->iterate_shared() for Btrfs because the delayed inode handling in btrfs_real_readdir() is racy. However, we can still do readdir in parallel if there are no delayed nodes. This is a temporary fix which upgrades the shared inode lock to an exclusive lock only when we have delayed items until we come up with a more complete solution. While we're here, rename the btrfs_{get,put}_delayed_items functions to make it very clear that they're just for readdir. Tested with xfstests and by doing a parallel kernel build: while make tinyconfig && make -j4 && git clean dqfx; do : done along with a bunch of parallel finds in another shell: while true; do for ((i=0; i<4; i++)); do find . >/dev/null & done wait done Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: David Sterba <dsterba@suse.com> Signed-off-by: Chris Mason <clm@fb.com>
Diffstat (limited to 'fs/btrfs/delayed-inode.c')
-rw-r--r--fs/btrfs/delayed-inode.c27
1 files changed, 22 insertions, 5 deletions
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 61561c2a3f96..d3aaabbfada0 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1606,15 +1606,23 @@ int btrfs_inode_delayed_dir_index_count(struct inode *inode)
return 0;
}
-void btrfs_get_delayed_items(struct inode *inode, struct list_head *ins_list,
- struct list_head *del_list)
+bool btrfs_readdir_get_delayed_items(struct inode *inode,
+ struct list_head *ins_list,
+ struct list_head *del_list)
{
struct btrfs_delayed_node *delayed_node;
struct btrfs_delayed_item *item;
delayed_node = btrfs_get_delayed_node(inode);
if (!delayed_node)
- return;
+ return false;
+
+ /*
+ * We can only do one readdir with delayed items at a time because of
+ * item->readdir_list.
+ */
+ inode_unlock_shared(inode);
+ inode_lock(inode);
mutex_lock(&delayed_node->mutex);
item = __btrfs_first_delayed_insertion_item(delayed_node);
@@ -1641,10 +1649,13 @@ void btrfs_get_delayed_items(struct inode *inode, struct list_head *ins_list,
* requeue or dequeue this delayed node.
*/
atomic_dec(&delayed_node->refs);
+
+ return true;
}
-void btrfs_put_delayed_items(struct list_head *ins_list,
- struct list_head *del_list)
+void btrfs_readdir_put_delayed_items(struct inode *inode,
+ struct list_head *ins_list,
+ struct list_head *del_list)
{
struct btrfs_delayed_item *curr, *next;
@@ -1659,6 +1670,12 @@ void btrfs_put_delayed_items(struct list_head *ins_list,
if (atomic_dec_and_test(&curr->refs))
kfree(curr);
}
+
+ /*
+ * The VFS is going to do up_read(), so we need to downgrade back to a
+ * read lock.
+ */
+ downgrade_write(&inode->i_rwsem);
}
int btrfs_should_delete_dir_index(struct list_head *del_list,