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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH v5 3/3] mm: Make filemap_release_folio() better inform shrink_folio_list() From: David Howells To: Matthew Wilcox Cc: Linus Torvalds , Steve French , Shyam Prasad N , Rohith Surabattula , Dave Wysochanski , Dominique Martinet , Ilya Dryomov , linux-cachefs@redhat.com, linux-cifs@vger.kernel.org, linux-afs@lists.infradead.org, v9fs-developer@lists.sourceforge.net, ceph-devel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, dhowells@redhat.com, Linus Torvalds , Jeff Layton , linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, linux-erofs@lists.ozlabs.org, linux-ext4@lists.ozlabs.org, linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 22 Dec 2022 15:02:29 +0000 Message-ID: <167172134962.2334525.570622889806603086.stgit@warthog.procyon.org.uk> In-Reply-To: <167172131368.2334525.8569808925687731937.stgit@warthog.procyon.org.uk> References: <167172131368.2334525.8569808925687731937.stgit@warthog.procyon.org.uk> User-Agent: StGit/1.5 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 107ED140011 X-Stat-Signature: b1zr7i6rcgjksxjatognd54mitjp6bp3 X-HE-Tag: 1671721359-277108 X-HE-Meta: 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 GyGf2S9t MlVGbVlDtzzVeLnha6Mxz5sIhCw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Make filemap_release_folio() return one of three values: (0) FILEMAP_CANT_RELEASE_FOLIO Couldn't release the folio's private data, so the folio can't itself be released. (1) FILEMAP_RELEASED_FOLIO The private data on the folio was released and the folio can be released. (2) FILEMAP_FOLIO_HAD_NO_PRIVATE There was no private data on the folio and the folio can be released. The first must be zero so that existing tests of !filemap_release_folio() continue to work as expected; similarly the other two must both be non-zero so that existing tests of filemap_release_folio() continue to work as expected. Using this, make shrink_folio_list() choose which of three cases to follow based on the return from filemap_release_folio() rather than testing the folio's private bit itself. Signed-off-by: David Howells cc: Matthew Wilcox cc: Linus Torvalds cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: Dave Wysochanski cc: Dominique Martinet cc: Ilya Dryomov cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-afs@lists.infradead.org cc: v9fs-developer@lists.sourceforge.net cc: ceph-devel@vger.kernel.org cc: linux-nfs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/1459152.1669208550@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/166924373637.1772793.2622483388224911574.stgit@warthog.procyon.org.uk/ # v4 --- include/linux/pagemap.h | 7 ++++++- mm/filemap.c | 20 ++++++++++++++------ mm/vmscan.c | 29 +++++++++++++++-------------- 3 files changed, 35 insertions(+), 21 deletions(-) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index a0d433e0addd..cd00fb3b524b 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -1121,7 +1121,12 @@ void __filemap_remove_folio(struct folio *folio, void *shadow); void replace_page_cache_folio(struct folio *old, struct folio *new); void delete_from_page_cache_batch(struct address_space *mapping, struct folio_batch *fbatch); -bool filemap_release_folio(struct folio *folio, gfp_t gfp); +enum filemap_released_folio { + FILEMAP_CANT_RELEASE_FOLIO = 0, /* (This must be 0) Release failed */ + FILEMAP_RELEASED_FOLIO = 1, /* Folio's private data released */ + FILEMAP_FOLIO_HAD_NO_PRIVATE = 2, /* Folio had no private data */ +}; +enum filemap_released_folio filemap_release_folio(struct folio *folio, gfp_t gfp); loff_t mapping_seek_hole_data(struct address_space *, loff_t start, loff_t end, int whence); diff --git a/mm/filemap.c b/mm/filemap.c index 344146c170b0..217ca847773a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3953,20 +3953,28 @@ EXPORT_SYMBOL(generic_file_write_iter); * this page (__GFP_IO), and whether the call may block * (__GFP_RECLAIM & __GFP_FS). * - * Return: %true if the release was successful, otherwise %false. + * Return: %FILEMAP_RELEASED_FOLIO if the release was successful, + * %FILEMAP_CANT_RELEASE_FOLIO if the private data couldn't be released and + * %FILEMAP_FOLIO_HAD_NO_PRIVATE if there was no private data. */ -bool filemap_release_folio(struct folio *folio, gfp_t gfp) +enum filemap_released_folio filemap_release_folio(struct folio *folio, + gfp_t gfp) { struct address_space * const mapping = folio->mapping; + bool released; BUG_ON(!folio_test_locked(folio)); if (!folio_needs_release(folio)) - return true; + return FILEMAP_FOLIO_HAD_NO_PRIVATE; if (folio_test_writeback(folio)) - return false; + return FILEMAP_CANT_RELEASE_FOLIO; if (mapping && mapping->a_ops->release_folio) - return mapping->a_ops->release_folio(folio, gfp); - return try_to_free_buffers(folio); + released = mapping->a_ops->release_folio(folio, gfp); + else + released = try_to_free_buffers(folio); + + return released ? + FILEMAP_RELEASED_FOLIO : FILEMAP_CANT_RELEASE_FOLIO; } EXPORT_SYMBOL(filemap_release_folio); diff --git a/mm/vmscan.c b/mm/vmscan.c index bded71961143..b1e5ca348223 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1996,25 +1996,26 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, * (refcount == 1) it can be freed. Otherwise, leave * the folio on the LRU so it is swappable. */ - if (folio_needs_release(folio)) { - if (!filemap_release_folio(folio, sc->gfp_mask)) - goto activate_locked; + switch (filemap_release_folio(folio, sc->gfp_mask)) { + case FILEMAP_CANT_RELEASE_FOLIO: + goto activate_locked; + case FILEMAP_RELEASED_FOLIO: if (!mapping && folio_ref_count(folio) == 1) { folio_unlock(folio); if (folio_put_testzero(folio)) goto free_it; - else { - /* - * rare race with speculative reference. - * the speculative reference will free - * this folio shortly, so we may - * increment nr_reclaimed here (and - * leave it off the LRU). - */ - nr_reclaimed += nr_pages; - continue; - } + /* + * rare race with speculative reference. the + * speculative reference will free this folio + * shortly, so we may increment nr_reclaimed + * here (and leave it off the LRU). + */ + nr_reclaimed += nr_pages; + continue; } + break; + case FILEMAP_FOLIO_HAD_NO_PRIVATE: + break; } if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) {