From: Qu Wenruo <w...@suse.com> commit 2e3c25136adfb293d517e17f761d3b8a43a8fc22 upstream.
This function needs some extra checks on locked pages and eb. For error handling we need to unlock locked pages and the eb. There is a rare >0 return value branch, where all pages get locked while write bio is not flushed. Thankfully it's handled by the only caller, btree_write_cache_pages(), as later write_one_eb() call will trigger submit_one_bio(). So there shouldn't be any problem. Signed-off-by: Qu Wenruo <w...@suse.com> Reviewed-by: David Sterba <dste...@suse.com> Signed-off-by: David Sterba <dste...@suse.com> Signed-off-by: Ben Hutchings <ben.hutchi...@codethink.co.uk> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- fs/btrfs/extent_io.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3554,19 +3554,27 @@ void wait_on_extent_buffer_writeback(str TASK_UNINTERRUPTIBLE); } +/* + * Lock eb pages and flush the bio if we can't the locks + * + * Return 0 if nothing went wrong + * Return >0 is same as 0, except bio is not submitted + * Return <0 if something went wrong, no page is locked + */ static noinline_for_stack int lock_extent_buffer_for_io(struct extent_buffer *eb, struct btrfs_fs_info *fs_info, struct extent_page_data *epd) { - int i, num_pages; + int i, num_pages, failed_page_nr; int flush = 0; int ret = 0; if (!btrfs_try_tree_write_lock(eb)) { - flush = 1; ret = flush_write_bio(epd); - BUG_ON(ret < 0); + if (ret < 0) + return ret; + flush = 1; btrfs_tree_lock(eb); } @@ -3576,7 +3584,8 @@ lock_extent_buffer_for_io(struct extent_ return 0; if (!flush) { ret = flush_write_bio(epd); - BUG_ON(ret < 0); + if (ret < 0) + return ret; flush = 1; } while (1) { @@ -3618,7 +3627,10 @@ lock_extent_buffer_for_io(struct extent_ if (!trylock_page(p)) { if (!flush) { ret = flush_write_bio(epd); - BUG_ON(ret < 0); + if (ret < 0) { + failed_page_nr = i; + goto err_unlock; + } flush = 1; } lock_page(p); @@ -3626,6 +3638,11 @@ lock_extent_buffer_for_io(struct extent_ } return ret; +err_unlock: + /* Unlock already locked pages */ + for (i = 0; i < failed_page_nr; i++) + unlock_page(eb->pages[i]); + return ret; } static void end_extent_buffer_writeback(struct extent_buffer *eb)