On Fri 13-08-21 11:18:01, Theodore Ts'o wrote: > On Wed, Aug 04, 2021 at 03:35:29PM +0200, Jan Kara wrote: > > On Wed 04-08-21 20:50:44, yangerkun wrote: > > > Our testcase(briefly described as fsstress on dm thin-provisioning which > > > ext4 see volume size with 100G but actual size 10G) trigger a hungtask > > > bug since ext4_writepages fall into a infinite loop: > > > > > > Got ENOSPC with follow stack: > > > ... > > > ext4_ext_map_blocks > > > ext4_ext_convert_to_initialized > > > ext4_ext_zeroout > > > ext4_issue_zeroout > > > ... > > > submit_bio_wait <-- bio to thinpool will return ENOSPC > > > > > > > Thanks for the patch. As a quick fix for the problem this is probably fine. > > But longer term we might need to implement a configurable behavior for this > > because just dropping data on the floor (which is what would happen here) > > need not be what sysadmin wants and blocking until space is provisioned may be > > actually a preferable behavior. Anyway for now feel free to add: > > > > Reviewed-by: Jan Kara <jack@xxxxxxx> > > Hmm, I wonder if this would be a better fix. (Not yet tested, may fry > your file system, etc....) What do folks think? Yes, that looks indeed better. I'd note that even splitting extent may fail due to ENOSPC on thin-provisioned storage but the chances are *much* lower. Honza > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index 92ad64b89d9b..501516cadc1b 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -3569,7 +3569,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, > split_map.m_len - ee_block); > err = ext4_ext_zeroout(inode, &zero_ex1); > if (err) > - goto out; > + goto fallback; > split_map.m_len = allocated; > } > if (split_map.m_lblk - ee_block + split_map.m_len < > @@ -3583,7 +3583,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, > ext4_ext_pblock(ex)); > err = ext4_ext_zeroout(inode, &zero_ex2); > if (err) > - goto out; > + goto fallback; > } > > split_map.m_len += split_map.m_lblk - ee_block; > @@ -3592,6 +3592,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, > } > } > > +fallback: > err = ext4_split_extent(handle, inode, ppath, &split_map, split_flag, > flags); > if (err > 0) -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
