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authorChunhai Guo <guochunhai@vivo.com>2023-09-16 06:51:31 +0200
committerChristian Brauner <brauner@kernel.org>2023-09-20 14:22:01 +0200
commitbe049c3a088d512187407b7fd036cecfab46d565 (patch)
tree178f9321a2a8e9e0492a0a5a31e02c19154067ba /fs/fs-writeback.c
parentaio: Annotate struct kioctx_table with __counted_by (diff)
downloadlinux-be049c3a088d512187407b7fd036cecfab46d565.tar.xz
linux-be049c3a088d512187407b7fd036cecfab46d565.zip
fs-writeback: do not requeue a clean inode having skipped pages
When writing back an inode and performing an fsync on it concurrently, a deadlock issue may arise as shown below. In each writeback iteration, a clean inode is requeued to the wb->b_dirty queue due to non-zero pages_skipped, without anything actually being written. This causes an infinite loop and prevents the plug from being flushed, resulting in a deadlock. We now avoid requeuing the clean inode to prevent this issue. wb_writeback fsync (inode-Y) blk_start_plug(&plug) for (;;) { iter i-1: some reqs with page-X added into plug->mq_list // f2fs node page-X with PG_writeback filemap_fdatawrite __filemap_fdatawrite_range // write inode-Y with sync_mode WB_SYNC_ALL do_writepages f2fs_write_data_pages __f2fs_write_data_pages // wb_sync_req[DATA]++ for WB_SYNC_ALL f2fs_write_cache_pages f2fs_write_single_data_page f2fs_do_write_data_page f2fs_outplace_write_data f2fs_update_data_blkaddr f2fs_wait_on_page_writeback wait_on_page_writeback // wait for f2fs node page-X iter i: progress = __writeback_inodes_wb(wb, work) . writeback_sb_inodes . __writeback_single_inode // write inode-Y with sync_mode WB_SYNC_NONE . . do_writepages . . f2fs_write_data_pages . . . __f2fs_write_data_pages // skip writepages due to (wb_sync_req[DATA]>0) . . . wbc->pages_skipped += get_dirty_pages(inode) // wbc->pages_skipped = 1 . if (!(inode->i_state & I_DIRTY_ALL)) // i_state = I_SYNC | I_SYNC_QUEUED . total_wrote++; // total_wrote = 1 . requeue_inode // requeue inode-Y to wb->b_dirty queue due to non-zero pages_skipped if (progress) // progress = 1 continue; iter i+1: queue_io // similar process with iter i, infinite for-loop ! } blk_finish_plug(&plug) // flush plug won't be called Signed-off-by: Chunhai Guo <guochunhai@vivo.com> Reviewed-by: Jan Kara <jack@suse.cz> Message-Id: <20230916045131.957929-1-guochunhai@vivo.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs/fs-writeback.c')
-rw-r--r--fs/fs-writeback.c11
1 files changed, 8 insertions, 3 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 969ce991b0b0..c1af01b2c42d 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1535,10 +1535,15 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
if (wbc->pages_skipped) {
/*
- * writeback is not making progress due to locked
- * buffers. Skip this inode for now.
+ * Writeback is not making progress due to locked buffers.
+ * Skip this inode for now. Although having skipped pages
+ * is odd for clean inodes, it can happen for some
+ * filesystems so handle that gracefully.
*/
- redirty_tail_locked(inode, wb);
+ if (inode->i_state & I_DIRTY_ALL)
+ redirty_tail_locked(inode, wb);
+ else
+ inode_cgwb_move_to_attached(inode, wb);
return;
}