From: Chao Yu chao@kernel.org
[ Upstream commit 344150999b7fc88502a65bbb147a47503eca2033 ]
Quoted from Jing Xia's report, there is a potential deadlock may happen between kworker and checkpoint as below:
[T:writeback] [T:checkpoint] - wb_writeback - blk_start_plug bio contains NodeA was plugged in writeback threads - do_writepages -- sync write inodeB, inc wb_sync_req[DATA] - f2fs_write_data_pages - f2fs_write_single_data_page -- write last dirty page - f2fs_do_write_data_page - set_page_writeback -- clear page dirty flag and PAGECACHE_TAG_DIRTY tag in radix tree - f2fs_outplace_write_data - f2fs_update_data_blkaddr - f2fs_wait_on_page_writeback -- wait NodeA to writeback here - inode_dec_dirty_pages - writeback_sb_inodes - writeback_single_inode - do_writepages - f2fs_write_data_pages -- skip writepages due to wb_sync_req[DATA] - wbc->pages_skipped += get_dirty_pages() -- PAGECACHE_TAG_DIRTY is not set but get_dirty_pages() returns one - requeue_inode -- requeue inode to wb->b_dirty queue due to non-zero.pages_skipped - blk_finish_plug
Let's try to avoid deadlock condition by forcing unplugging previous bio via blk_finish_plug(current->plug) once we'v skipped writeback in writepages() due to valid sbi->wb_sync_req[DATA/NODE].
Fixes: 687de7f1010c ("f2fs: avoid IO split due to mixed WB_SYNC_ALL and WB_SYNC_NONE") Signed-off-by: Zhiguo Niu zhiguo.niu@unisoc.com Signed-off-by: Jing Xia jing.xia@unisoc.com Signed-off-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/f2fs/data.c | 6 +++++- fs/f2fs/node.c | 6 +++++- 2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 8c417864c66a..e1ef925be60c 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -3163,8 +3163,12 @@ static int __f2fs_write_data_pages(struct address_space *mapping, /* to avoid spliting IOs due to mixed WB_SYNC_ALL and WB_SYNC_NONE */ if (wbc->sync_mode == WB_SYNC_ALL) atomic_inc(&sbi->wb_sync_req[DATA]); - else if (atomic_read(&sbi->wb_sync_req[DATA])) + else if (atomic_read(&sbi->wb_sync_req[DATA])) { + /* to avoid potential deadlock */ + if (current->plug) + blk_finish_plug(current->plug); goto skip_write; + }
if (__should_serialize_io(inode, wbc)) { mutex_lock(&sbi->writepages); diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index 50b2874e758c..4ff7dfb54250 100644 --- a/fs/f2fs/node.c +++ b/fs/f2fs/node.c @@ -2111,8 +2111,12 @@ static int f2fs_write_node_pages(struct address_space *mapping,
if (wbc->sync_mode == WB_SYNC_ALL) atomic_inc(&sbi->wb_sync_req[NODE]); - else if (atomic_read(&sbi->wb_sync_req[NODE])) + else if (atomic_read(&sbi->wb_sync_req[NODE])) { + /* to avoid potential deadlock */ + if (current->plug) + blk_finish_plug(current->plug); goto skip_write; + }
trace_f2fs_writepages(mapping->host, wbc, NODE);