Re: [PATCH 01/10] iomap: handle a post-direct I/O invalidate race in iomap_write_delalloc_release

Darrick J. Wong
2024-08-29T14:22:20Z

On Thu, Aug 29, 2024 at 05:46:26AM +0200, Christoph Hellwig wrote:
> On Wed, Aug 28, 2024 at 09:13:38AM -0700, Darrick J. Wong wrote:
> > Though we might have to revisit this for filesystems that don't take
> > i_rwsem exclusively when writing -- is that a problem? I guess if you
> > had two threads both writing and punching the pagecache they could get
> > into trouble, but that might be a case of "if it hurts don't do that".
>
> No i_rwsem for buffered writes? You can't really do that without hell
> breaking lose. At least not without another exclusive lock.

Well, i_rwsem in shared mode. ISTR ext4 does inode_lock_shared and
serializes on the folio lock, at least for non extending writes.

--D