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 --- fs/fs-writeback.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 591fe9cf1659..1fae0196292a 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1712,6 +1712,10 @@ static int writeback_single_inode(struct inode *inode, */ 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: