From 953fa5ced510c4937075002bbfc6405cd500efef Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 24 Jul 2023 07:22:38 -0700 Subject: [PATCH] btrfs: fix error handling when in a COW window in run_delalloc_nocow When run_delalloc_nocow has cow_start set to a value other than (u64)-1, it has delayed COW writeback pending behind cur_offset. When an error occurs in such a window, the range going back to cow_start and not just cur_offset needs to be unlocked, but only two error cases handle this correctly Move the code to handle unlock the COW range to the common error handling label and document the logic. To make things even more complicated, cow_file_range as called by fallback_to_cow will unlock the range it is operating on when it fails as well, so we need to reset cow_start right after caling fallback_to_cow instead of only when it succeeded. Reviewed-by: Boris Burkov Signed-off-by: Christoph Hellwig Signed-off-by: David Sterba --- fs/btrfs/inode.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index f2ab270..0d973a9 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -2029,11 +2029,8 @@ next_slot: leaf = path->nodes[0]; if (path->slots[0] >= btrfs_header_nritems(leaf)) { ret = btrfs_next_leaf(root, path); - if (ret < 0) { - if (cow_start != (u64)-1) - cur_offset = cow_start; + if (ret < 0) goto error; - } if (ret > 0) break; leaf = path->nodes[0]; @@ -2096,13 +2093,10 @@ next_slot: nocow_args.start = cur_offset; ret = can_nocow_file_extent(path, &found_key, inode, &nocow_args); - if (ret < 0) { - if (cow_start != (u64)-1) - cur_offset = cow_start; + if (ret < 0) goto error; - } else if (ret == 0) { + if (ret == 0) goto out_check; - } ret = 0; bg = btrfs_inc_nocow_writers(fs_info, nocow_args.disk_bytenr); @@ -2133,9 +2127,9 @@ out_check: if (cow_start != (u64)-1) { ret = fallback_to_cow(inode, locked_page, cow_start, found_key.offset - 1); + cow_start = (u64)-1; if (ret) goto error; - cow_start = (u64)-1; } nocow_end = cur_offset + nocow_args.num_bytes - 1; @@ -2214,6 +2208,7 @@ out_check: if (cow_start != (u64)-1) { cur_offset = end; ret = fallback_to_cow(inode, locked_page, cow_start, end); + cow_start = (u64)-1; if (ret) goto error; } @@ -2222,6 +2217,13 @@ error: if (nocow) btrfs_dec_nocow_writers(bg); + /* + * If an error happened while a COW region is outstanding, cur_offset + * needs to be reset to cow_start to ensure the COW region is unlocked + * as well. + */ + if (cow_start != (u64)-1) + cur_offset = cow_start; if (ret && cur_offset < end) extent_clear_unlock_delalloc(inode, cur_offset, end, locked_page, EXTENT_LOCKED | -- 2.7.4