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 <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
CC: [email protected]
Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option")
Signed-off-by: Jing Xia <[email protected]>
---
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:
--
2.17.1
On Tue 10-05-22 10:35:14, Jing Xia wrote:
> 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 <[email protected]>
> Reviewed-by: Christoph Hellwig <[email protected]>
> CC: [email protected]
> Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option")
> Signed-off-by: Jing Xia <[email protected]>
Thanks. I've queued the patch to my tree and will push it to Linus tomorrow
or so.
Honza
> ---
> 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:
> --
> 2.17.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR