[Linux-cachefs] [PATCH v6 0/2] mm, netfs, fscache: Stop read optimisation when folio removed from pagecache

[David Wysochanski]

On Tue, May 16, 2023 at 3:29 PM David Wysochanski <dwysocha at redhat.com> wrote:
>
> On Thu, Feb 16, 2023 at 10:07 AM David Howells <dhowells at redhat.com> wrote:
> >
> > Hi Willy,
> >
> > Is this okay by you?  You said you wanted to look at the remaining uses of
> > page_has_private(), of which there are then three after these patches, not
> > counting folio_has_private():
> >
> >         arch/s390/kernel/uv.c:          if (page_has_private(page))
> >         mm/khugepaged.c:                    1 + page_mapcount(page) + page_has_private(page)) {
> >         mm/migrate_device.c:            extra += 1 + page_has_private(page);
> >
> > --
> > I've split the folio_has_private()/filemap_release_folio() call pair
> > merging into its own patch, separate from the actual bugfix and pulled out
> > the folio_needs_release() function into mm/internal.h and made
> > filemap_release_folio() use it.  I've also got rid of the bit clearances
> > from the network filesystem evict_inode functions as they doesn't seem to
> > be necessary.
> >
> > Note that the last vestiges of try_to_release_page() got swept away, so I
> > rebased and dealt with that.  One comment remained, which is removed by the
> > first patch.
> >
> > David
> >
> > Changes:
> > ========
> > ver #6)
> >  - Drop the third patch which removes a duplicate check in vmscan().
> >
> > ver #5)
> >  - Rebased on linus/master.  try_to_release_page() has now been entirely
> >    replaced by filemap_release_folio(), barring one comment.
> >  - Cleaned up some pairs in ext4.
> >
> > ver #4)
> >  - Split has_private/release call pairs into own patch.
> >  - Moved folio_needs_release() to mm/internal.h and removed open-coded
> >    version from filemap_release_folio().
> >  - Don't need to clear AS_RELEASE_ALWAYS in ->evict_inode().
> >  - Added experimental patch to reduce shrink_folio_list().
> >
> > ver #3)
> >  - Fixed mapping_clear_release_always() to use clear_bit() not set_bit().
> >  - Moved a '&&' to the correct line.
> >
> > ver #2)
> >  - Rewrote entirely according to Willy's suggestion[1].
> >
> > Link: https://lore.kernel.org/r/Yk9V/03wgdYi65Lb@casper.infradead.org/ [1]
> > Link: https://lore.kernel.org/r/164928630577.457102.8519251179327601178.stgit@warthog.procyon.org.uk/ # v1
> > Link: https://lore.kernel.org/r/166844174069.1124521.10890506360974169994.stgit@warthog.procyon.org.uk/ # v2
> > Link: https://lore.kernel.org/r/166869495238.3720468.4878151409085146764.stgit@warthog.procyon.org.uk/ # v3
> > Link: https://lore.kernel.org/r/1459152.1669208550@warthog.procyon.org.uk/ # v3 also
> > Link: https://lore.kernel.org/r/166924370539.1772793.13730698360771821317.stgit@warthog.procyon.org.uk/ # v4
> > Link: https://lore.kernel.org/r/167172131368.2334525.8569808925687731937.stgit@warthog.procyon.org.uk/ # v5
> > ---
> > %(shortlog)s
> > %(diffstat)s
> >
> > David Howells (2):
> >   mm: Merge folio_has_private()/filemap_release_folio() call pairs
> >   mm, netfs, fscache: Stop read optimisation when folio removed from
> >     pagecache
> >
> >  fs/9p/cache.c           |  2 ++
> >  fs/afs/internal.h       |  2 ++
> >  fs/cachefiles/namei.c   |  2 ++
> >  fs/ceph/cache.c         |  2 ++
> >  fs/cifs/fscache.c       |  2 ++
> >  fs/ext4/move_extent.c   | 12 ++++--------
> >  fs/splice.c             |  3 +--
> >  include/linux/pagemap.h | 16 ++++++++++++++++
> >  mm/filemap.c            |  2 ++
> >  mm/huge_memory.c        |  3 +--
> >  mm/internal.h           | 11 +++++++++++
> >  mm/khugepaged.c         |  3 +--
> >  mm/memory-failure.c     |  8 +++-----
> >  mm/migrate.c            |  3 +--
> >  mm/truncate.c           |  6 ++----
> >  mm/vmscan.c             |  8 ++++----
> >  16 files changed, 56 insertions(+), 29 deletions(-)
> >
> > --
> > Linux-cachefs mailing list
> > Linux-cachefs at redhat.com
> > https://listman.redhat.com/mailman/listinfo/linux-cachefs
> >
>
> Willy, and David,
>
> Can this series move forward?
> This just got mentioned again [1] after Chris tested the NFS netfs
> patches that were merged in 6.4-rc1
>
> [1] https://lore.kernel.org/linux-nfs/CAAmbk-f_U8CPcTQM866L572uUHdK4p5iWKnUQs4r8fkW=6RW9g@mail.gmail.com/

Sorry about the timing on the original email as I forgot it lined up
with LSF/MM.

FYI, I tested with 6.4-rc1 plus these two patches, then I added the NFS
hunk needed (see below).  All my tests pass now[1], and it makes sense
from all the ftraces I've seen on test runs that fail (cachefiles_prep_read
trace event would show "DOWN no-data" even after data was written
previously).

This small NFS hunk needs added to patch #2 in this series:

diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index 8c35d88a84b1..d4a20748b14f 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -180,6 +180,10 @@ void nfs_fscache_init_inode(struct inode *inode)
                                               &auxdata,      /* aux_data */
                                               sizeof(auxdata),
                                               i_size_read(inode));
+
+       if (netfs_inode(inode)->cache)
+               mapping_set_release_always(inode->i_mapping);
+
 }

 /*

[1] https://lore.kernel.org/linux-nfs/CALF+zOn_qX4tcT2ucq4jD3G-1ERqZkL6Cw7hx75OnQF0ivqSeA@mail.gmail.com/