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authorJosef Bacik <josef@toxicpanda.com>2017-10-19 14:16:01 -0400
committerDavid Sterba <dsterba@suse.com>2017-11-01 20:45:35 +0100
commitce8ea7cc6eb3139f4c730d647325e69354159b0f (patch)
tree22c6c34e55ce1dabf8ca7d5d81205828f387ea51 /fs/btrfs
parent0e0adbcfdc908684317c99a9bf5e13383f03b7ec (diff)
downloadlinux-ce8ea7cc6eb3139f4c730d647325e69354159b0f.tar.bz2
btrfs: don't call btrfs_start_delalloc_roots in flushoncommit
We're holding the sb_start_intwrite lock at this point, and doing async filemap_flush of the inodes will result in a deadlock if we freeze the fs during this operation. This is because we could do a btrfs_join_transaction() in the thread we are waiting on which would block at sb_start_intwrite, and thus deadlock. Using writeback_inodes_sb() side steps the problem by not introducing all of these extra locking dependencies. Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
-rw-r--r--fs/btrfs/transaction.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 68c3e1c04bca..5a8c2649af2f 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1916,8 +1916,17 @@ static void cleanup_transaction(struct btrfs_trans_handle *trans,
static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
{
+ /*
+ * We use writeback_inodes_sb here because if we used
+ * btrfs_start_delalloc_roots we would deadlock with fs freeze.
+ * Currently are holding the fs freeze lock, if we do an async flush
+ * we'll do btrfs_join_transaction() and deadlock because we need to
+ * wait for the fs freeze lock. Using the direct flushing we benefit
+ * from already being in a transaction and our join_transaction doesn't
+ * have to re-take the fs freeze lock.
+ */
if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
- return btrfs_start_delalloc_roots(fs_info, 1, -1);
+ writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
return 0;
}