From: Josef Bacik <josef@toxicpanda.com>
To: linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH] btrfs: honor path->skip_locking in backref code
Date: Wed, 16 Jan 2019 11:00:57 -0500 [thread overview]
Message-ID: <20190116160057.22040-1-josef@toxicpanda.com> (raw)
qgroups will do the old roots lookup at delayed ref time, which could be
while walking down the extent root while running a delayed ref. This
should be fine, except we specifically lock eb's in the backref walking
code irrespective of path->skip_locking, which deadlocks the system.
Fix up the backref code to honor path->skip_locking, nobody will be
modifying the commit_root when we're searching so it's completely safe
to do. Thanks,
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/backref.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 78556447e1d5..973e8251b1bf 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -712,7 +712,7 @@ static int resolve_indirect_refs(struct btrfs_fs_info *fs_info,
* read tree blocks and add keys where required.
*/
static int add_missing_keys(struct btrfs_fs_info *fs_info,
- struct preftrees *preftrees)
+ struct preftrees *preftrees, bool lock)
{
struct prelim_ref *ref;
struct extent_buffer *eb;
@@ -737,12 +737,14 @@ static int add_missing_keys(struct btrfs_fs_info *fs_info,
free_extent_buffer(eb);
return -EIO;
}
- btrfs_tree_read_lock(eb);
+ if (lock)
+ btrfs_tree_read_lock(eb);
if (btrfs_header_level(eb) == 0)
btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
else
btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
- btrfs_tree_read_unlock(eb);
+ if (lock)
+ btrfs_tree_read_unlock(eb);
free_extent_buffer(eb);
prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
cond_resched();
@@ -1227,7 +1229,7 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
btrfs_release_path(path);
- ret = add_missing_keys(fs_info, &preftrees);
+ ret = add_missing_keys(fs_info, &preftrees, path->skip_locking == 0);
if (ret)
goto out;
@@ -1288,11 +1290,13 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
ret = -EIO;
goto out;
}
- btrfs_tree_read_lock(eb);
+ if (!path->skip_locking)
+ btrfs_tree_read_lock(eb);
btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
ret = find_extent_in_eb(eb, bytenr,
*extent_item_pos, &eie, ignore_offset);
- btrfs_tree_read_unlock_blocking(eb);
+ if (!path->skip_locking)
+ btrfs_tree_read_unlock_blocking(eb);
free_extent_buffer(eb);
if (ret < 0)
goto out;
--
2.14.3
next reply other threads:[~2019-01-16 16:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 16:00 Josef Bacik [this message]
2019-01-17 1:04 ` [PATCH] btrfs: honor path->skip_locking in backref code Qu Wenruo
2019-01-17 14:30 ` David Sterba
2019-01-17 14:38 ` Qu Wenruo
2019-01-17 15:23 ` David Sterba
2019-01-18 13:39 ` David Sterba
2019-01-23 13:51 ` David Sterba
2019-02-12 5:07 ` Qu Wenruo
2019-02-12 14:19 ` David Sterba
2019-02-12 14:25 ` Qu Wenruo
2019-05-28 10:15 Qu Wenruo
2019-05-28 16:10 ` David Sterba
2019-05-28 10:18 Qu Wenruo
2019-05-28 16:10 ` David Sterba
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