| From 846a3351ddfe4a86eede4bb26a205c3f38ef84d3 Mon Sep 17 00:00:00 2001 |
| From: Jing Xia <jing.xia@unisoc.com> |
| Date: Tue, 10 May 2022 10:35:14 +0800 |
| Subject: writeback: Avoid skipping inode writeback |
| |
| From: Jing Xia <jing.xia@unisoc.com> |
| |
| commit 846a3351ddfe4a86eede4bb26a205c3f38ef84d3 upstream. |
| |
| We have run into an issue that a task gets stuck in |
| balance_dirty_pages_ratelimited() when perform I/O stress testing. |
| The reason we observed is that an I_DIRTY_PAGES inode with lots |
| of dirty pages is in b_dirty_time list and standard background |
| writeback cannot writeback the inode. |
| After studing the relevant code, the following scenario may lead |
| to the issue: |
| |
| task1 task2 |
| ----- ----- |
| fuse_flush |
| write_inode_now //in b_dirty_time |
| writeback_single_inode |
| __writeback_single_inode |
| fuse_write_end |
| filemap_dirty_folio |
| __xa_set_mark:PAGECACHE_TAG_DIRTY |
| lock inode->i_lock |
| if mapping tagged PAGECACHE_TAG_DIRTY |
| inode->i_state |= I_DIRTY_PAGES |
| unlock inode->i_lock |
| __mark_inode_dirty:I_DIRTY_PAGES |
| lock inode->i_lock |
| -was dirty,inode stays in |
| -b_dirty_time |
| unlock inode->i_lock |
| |
| if(!(inode->i_state & I_DIRTY_All)) |
| -not true,so nothing done |
| |
| This patch moves the dirty inode to b_dirty list when the inode |
| currently is not queued in b_io or b_more_io list at the end of |
| writeback_single_inode. |
| |
| Reviewed-by: Jan Kara <jack@suse.cz> |
| Reviewed-by: Christoph Hellwig <hch@lst.de> |
| CC: stable@vger.kernel.org |
| Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option") |
| Signed-off-by: Jing Xia <jing.xia@unisoc.com> |
| Signed-off-by: Jan Kara <jack@suse.cz> |
| Link: https://lore.kernel.org/r/20220510023514.27399-1-jing.xia@unisoc.com |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| fs/fs-writeback.c | 4 ++++ |
| 1 file changed, 4 insertions(+) |
| |
| --- a/fs/fs-writeback.c |
| +++ b/fs/fs-writeback.c |
| @@ -1739,6 +1739,10 @@ static int writeback_single_inode(struct |
| */ |
| if (!(inode->i_state & I_DIRTY_ALL)) |
| inode_cgwb_move_to_attached(inode, wb); |
| + else if (!(inode->i_state & I_SYNC_QUEUED) && |
| + (inode->i_state & I_DIRTY)) |
| + redirty_tail_locked(inode, wb); |
| + |
| spin_unlock(&wb->list_lock); |
| inode_sync_complete(inode); |
| out: |
