Re: [Cluster-devel] [PATCH v11 16/25] fs: Convert mpage_readpages to mpage_readahead

[Andreas GrÃnbacher]

Am Mi., 17. Juni 2020 um 02:33 Uhr schrieb Matthew Wilcox <willy@xxxxxxxxxxxxx>:
>
> On Wed, Jun 17, 2020 at 12:36:13AM +0200, Andreas Gruenbacher wrote:
> > Am Mi., 15. Apr. 2020 um 23:39 Uhr schrieb Matthew Wilcox <willy@xxxxxxxxxxxxx>:
> > > From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> > >
> > > Implement the new readahead aop and convert all callers (block_dev,
> > > exfat, ext2, fat, gfs2, hpfs, isofs, jfs, nilfs2, ocfs2, omfs, qnx6,
> > > reiserfs & udf).  The callers are all trivial except for GFS2 & OCFS2.
> >
> > This patch leads to an ABBA deadlock in xfstest generic/095 on gfs2.
> >
> > Our lock hierarchy is such that the inode cluster lock ("inode glock")
> > for an inode needs to be taken before any page locks in that inode's
> > address space.
>
> How does that work for ...
>
> writepage:              yes, unlocks (see below)
> readpage:               yes, unlocks
> invalidatepage:         yes
> releasepage:            yes
> freepage:               yes
> isolate_page:           yes
> migratepage:            yes (both)
> putback_page:           yes
> launder_page:           yes
> is_partially_uptodate:  yes
> error_remove_page:      yes
>
> Is there a reason that you don't take the glock in the higher level
> ops which are called before readhead gets called?  I'm looking at XFS,
> and it takes the xfs_ilock SHARED in xfs_file_buffered_aio_read()
> (called from xfs_file_read_iter).

Right, the approach from the following thread might fix this:

https://lore.kernel.org/linux-fsdevel/20191122235324.17245-1-agruenba@xxxxxxxxxx/T/#t

Andreas