From: Josef Bacik Date: Thu, 19 Oct 2017 18:16:01 +0000 (-0400) Subject: btrfs: don't call btrfs_start_delalloc_roots in flushoncommit X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=ce8ea7cc6eb3139f4c730d647325e69354159b0f;p=openwrt%2Fstaging%2Fblogic.git 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 Signed-off-by: David Sterba --- 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; }