From patchwork Thu Mar 2 23:16:36 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13158039 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27FDCC7EE30 for ; Thu, 2 Mar 2023 23:18:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229596AbjCBXSW (ORCPT ); Thu, 2 Mar 2023 18:18:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229830AbjCBXSP (ORCPT ); Thu, 2 Mar 2023 18:18:15 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BD4A758B43 for ; Thu, 2 Mar 2023 15:17:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677799012; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1eE9Pafa530L5JjpUU74EsDdw6S9K1gsLvm9PBz92W8=; b=e5UibSOrWGxcxGg2l4E3lQMiSC1vlGR9bBNe4k4Xs0e4w/tEBHZWvaouNgCKh5KXj4bFMG 8Ys+EikQqRfQrcspmFb2sOoqBxSsAyqf0Poi0BA0SIjFAOdw7ZtJGPv/6kveQcpYEK8z1O vUeSrDSMlaDIn9EU6KQSSsgLkSZVI1E= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-622-zwFLchJEPOeBqPxHgNImPw-1; Thu, 02 Mar 2023 18:16:47 -0500 X-MC-Unique: zwFLchJEPOeBqPxHgNImPw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 630DB800B23; Thu, 2 Mar 2023 23:16:46 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id 54038440D9; Thu, 2 Mar 2023 23:16:44 +0000 (UTC) From: David Howells To: Linus Torvalds , Steve French Cc: David Howells , Vishal Moola , Shyam Prasad N , Rohith Surabattula , Tom Talpey , Stefan Metzmacher , Paulo Alcantara , Jeff Layton , Matthew Wilcox , Marc Dionne , linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Steve French , Andrew Morton , linux-mm@kvack.org Subject: [PATCH 1/3] mm: Add a function to get a single tagged folio from a file Date: Thu, 2 Mar 2023 23:16:36 +0000 Message-Id: <20230302231638.521280-2-dhowells@redhat.com> In-Reply-To: <20230302231638.521280-1-dhowells@redhat.com> References: <20230302231638.521280-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Add a function to get a single tagged folio from a file rather than a batch for use in afs and cifs where, in the common case, the batch is likely to be rendered irrelevant by the {afs,cifs}_extend_writeback() function. For filemap_get_folios_tag() to be of use, the batch has to be passed down, and if it contains scattered, non-contiguous folios, these are likely to end up being pinned by the batch for significant periods of time whilst I/O is undertaken on earlier pages. Further, for write_cache_pages() to be useful, it would need to wait for PG_fscache which is used to indicate that I/O is in progress from a folio to the cache - but it can't do this unconditionally as some filesystems, such as btrfs, use PG_private_2 for other purposes. Signed-off-by: David Howells cc: Steve French cc: Linus Torvalds cc: "Vishal Moola (Oracle)" cc: "Matthew Wilcox (Oracle)" cc: Andrew Morton cc: linux-afs@lists.infradead.org cc: linux-cifs@vger.kernel.org cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/2214157.1677250083@warthog.procyon.org.uk/ --- include/linux/pagemap.h | 2 ++ mm/filemap.c | 58 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 60 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 0acb8e1fb7af..577535633006 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -741,6 +741,8 @@ unsigned filemap_get_folios_contig(struct address_space *mapping, pgoff_t *start, pgoff_t end, struct folio_batch *fbatch); unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start, pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch); +struct folio *filemap_get_folio_tag(struct address_space *mapping, pgoff_t *start, + pgoff_t end, xa_mark_t tag); struct page *grab_cache_page_write_begin(struct address_space *mapping, pgoff_t index); diff --git a/mm/filemap.c b/mm/filemap.c index 2723104cc06a..1b1e9c661018 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2339,6 +2339,64 @@ unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start, } EXPORT_SYMBOL(filemap_get_folios_tag); +/** + * filemap_get_folio_tag - Get the first folio matching @tag + * @mapping: The address_space to search + * @start: The starting page index + * @end: The final page index (inclusive) + * @tag: The tag index + * + * Search for and return the first folios in the mapping starting at index + * @start and up to index @end (inclusive). The folio is returned with an + * elevated reference count. + * + * If a folio is returned, it may start before @start; if it does, it will + * contain @start. The folio may also extend beyond @end; if it does, it will + * contain @end. If folios are added to or removed from the page cache while + * this is running, they may or may not be found by this call. + * + * Return: The folio that was found or NULL. @start is also updated to index + * the next folio for the traversal or will be left pointing after @end. + */ +struct folio *filemap_get_folio_tag(struct address_space *mapping, pgoff_t *start, + pgoff_t end, xa_mark_t tag) +{ + XA_STATE(xas, &mapping->i_pages, *start); + struct folio *folio; + + rcu_read_lock(); + while ((folio = find_get_entry(&xas, end, tag)) != NULL) { + /* + * Shadow entries should never be tagged, but this iteration + * is lockless so there is a window for page reclaim to evict + * a page we saw tagged. Skip over it. + */ + if (xa_is_value(folio)) + continue; + + if (folio_test_hugetlb(folio)) + *start = folio->index + 1; + else + *start = folio_next_index(folio); + goto out; + } + + /* + * We come here when there is no page beyond @end. We take care to not + * overflow the index @start as it confuses some of the callers. This + * breaks the iteration when there is a page at index -1 but that is + * already broke anyway. + */ + if (end == (pgoff_t)-1) + *start = (pgoff_t)-1; + else + *start = end + 1; +out: + rcu_read_unlock(); + return folio; +} +EXPORT_SYMBOL(filemap_get_folio_tag); + /* * CD/DVDs are error prone. When a medium error occurs, the driver may fail * a _large_ part of the i/o request. Imagine the worst scenario: