Hi Andrew, Should this go through the mm tree? This fixes an optimisation in fscache whereby we don't read from the cache for a particular file until we know that there's data there that we don't have in the pagecache. The problem is that I'm no longer using PG_fscache (aka PG_private_2) to indicate that the page is cached and so I don't get a notification when a cached page is dropped from the pagecache. The first patch merges some folio_has_private() and filemap_release_folio() pairs and introduces a helper, folio_needs_release(), to indicate if a release is required. The second patch is the actual fix. Following Willy's suggestions[1], it adds an AS_RELEASE_ALWAYS flag to an address_space that will make filemap_release_folio() always call ->release_folio(), even if PG_private/PG_private_2 aren't set. folio_needs_release() is altered to add a check for this. David Changes: ======== ver #7) - Make NFS set AS_RELEASE_ALWAYS. 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@xxxxxxxxxxxxxxxxxxxx/ [1] Link: https://lore.kernel.org/r/164928630577.457102.8519251179327601178.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v1 Link: https://lore.kernel.org/r/166844174069.1124521.10890506360974169994.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v2 Link: https://lore.kernel.org/r/166869495238.3720468.4878151409085146764.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v3 Link: https://lore.kernel.org/r/1459152.1669208550@xxxxxxxxxxxxxxxxxxxxxx/ # v3 also Link: https://lore.kernel.org/r/166924370539.1772793.13730698360771821317.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v4 Link: https://lore.kernel.org/r/167172131368.2334525.8569808925687731937.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v5 Link: https://lore.kernel.org/r/20230216150701.3654894-1-dhowells@xxxxxxxxxx/ # v6 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/ext4/move_extent.c | 12 ++++-------- fs/nfs/fscache.c | 3 +++ fs/smb/client/fscache.c | 2 ++ 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 ++++---- 17 files changed, 59 insertions(+), 29 deletions(-)
