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Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH v4 3/3] mm: Make filemap_release_folio() better inform shrink_folio_list() From: David Howells To: Linus Torvalds Cc: Matthew Wilcox , 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, Matthew Wilcox , 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-cachefs@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 23 Nov 2022 22:48:56 +0000 Message-ID: <166924373637.1772793.2622483388224911574.stgit@warthog.procyon.org.uk> In-Reply-To: <166924370539.1772793.13730698360771821317.stgit@warthog.procyon.org.uk> References: <166924370539.1772793.13730698360771821317.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 10.11.54.3 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669243746; a=rsa-sha256; cv=none; b=ydcan+Ml+RXahZt6CpC5Sq8bTlkJTynlDvkEalmKbC+VOpgLbA0/e6+FORWMHk6D+LdDA5 EiaUrZ079YKvwMQRWyXFvB8wNBu6MHT9bgFu9lzQWi/dyU4ddiHk3dR/36h8HhBeVvEITV mjrBc38V872TO2250TBC2+9vWy5TQQw= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=QvlLSfsA; spf=pass (imf23.hostedemail.com: domain of dhowells@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=dhowells@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669243746; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=WHpeeqm1MJ8TYn1nRD3MVhIBofwqjS4Ni77i3McPwEA=; b=6Bnhln9xvdjjsiPuoYR1kv1dfpqUp3AR7KEoJqzY69eAxwL6pa15bkwaNKZj7hNwkQsRiS ONvlXK2fyQZsvsJCiXGzk8xKB4CBt1DLnSoKB/aKyTmzz0a2CCrPlXIC7iX5fp2WYKwmJY BbneYv/Aw1gtzaTggll414BmJVksH1Q= X-Rspam-User: X-Rspamd-Queue-Id: 55C4E140004 Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=QvlLSfsA; spf=pass (imf23.hostedemail.com: domain of dhowells@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=dhowells@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Stat-Signature: 8p7t6p3drjqxump9pgsqzzkrf9yz66aj X-Rspamd-Server: rspam10 X-HE-Tag: 1669243746-260217 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 --- 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 9a824b43c6af..b763182b6d3f 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -1124,7 +1124,12 @@ void replace_page_cache_page(struct page *old, struct page *new); void delete_from_page_cache_batch(struct address_space *mapping, struct folio_batch *fbatch); int try_to_release_page(struct page *page, gfp_t gfp); -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 93757247cd11..859831c70439 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3934,20 +3934,28 @@ 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 b9316f447238..d5c7b3be9947 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1978,25 +1978,26 @@ 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)) {