From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E456C07E85 for ; Tue, 11 Dec 2018 17:38:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F10932086D for ; Tue, 11 Dec 2018 17:38:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=toxicpanda-com.20150623.gappssmtp.com header.i=@toxicpanda-com.20150623.gappssmtp.com header.b="dElFjUL6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F10932086D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=toxicpanda.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726929AbeLKRiL (ORCPT ); Tue, 11 Dec 2018 12:38:11 -0500 Received: from mail-yw1-f65.google.com ([209.85.161.65]:37383 "EHLO mail-yw1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726620AbeLKRiJ (ORCPT ); Tue, 11 Dec 2018 12:38:09 -0500 Received: by mail-yw1-f65.google.com with SMTP id h193so5774719ywc.4 for ; Tue, 11 Dec 2018 09:38:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toxicpanda-com.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id:in-reply-to:references; bh=im1lOdR1gtAkoa5Y+U3jnYHZp+MThsPseW0SoznaozY=; b=dElFjUL6mOWqvfIN7pdHq7KvdZA/TSnmClfaII8u1KnK8lIDouqSSwhJtv6wLAYSOd psu68HLy6vx5qGKAD+FNvOYuyesDwSpolLB537QXJbQKwvHpmTSfPxGxd0ie62LyOsCC bPhbIN2J9w1tFmkIljNhcJjwG/uftGhyT+LsISUVoDJigICYVwZH01j2GhAcX3rRW/Fm BIPFOk7G8nUUpHBATObKMzuKipM1jsmXCHQ5TF0C9pJEvQx2gIY3Gqdswaq0leQD6qA0 8s28SZADVdA4PAF0Vhn5vnPOdVA1ssWBoS8ZuKiY4rCAGueaUKtckTaNkxe0Zf1QiBXO /hCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references; bh=im1lOdR1gtAkoa5Y+U3jnYHZp+MThsPseW0SoznaozY=; b=RZYDDcGk79TxfXgbmiGmAFLmCOqatsa4ABDlZVlpk4yHpG3RWjeDwjrRvhGAnp/+tC HBSa3Pgx56hLHTDr2TWYvCq9H3OyJSDkRfB36KoZbqy2NJNlh+e0EUPVs1T8Udw+nSSt utm5l8/MrEXAtyOXLHCu0oPLzv2VJ2OJ2hVQHKK7AEBtrHX6SBB9rI5PvjBjtBKuIvrN k5QfUjlzGiV20ReL758/Yi1/FoAYXayXS+HHOhmpV9KgTFtk8T9zAddjWHHfC3R2AZGq zkAY9slKd8mGprov3wMRsO33o5AFbrWPm9Y0/EyVW9Q3M2dL6GEmBSIDzAQXo8uoN2Hb 7lYA== X-Gm-Message-State: AA+aEWa2j9jeyGGQk6QqsHrOy4OKdsHcreaRanlVquchsBPVwWV9H9WZ 9M0GsuNrCmPlLTwc7kDKB7xG7Q== X-Google-Smtp-Source: AFSGD/UWgQfH/IFA1ziDeQtpo/Az3ijAiizbIBHDC5CCjFtCTgcbOB9TMHT4hPOe6zI/ZWoFy+YT2g== X-Received: by 2002:a81:56d7:: with SMTP id k206mr17467616ywb.167.1544549887505; Tue, 11 Dec 2018 09:38:07 -0800 (PST) Received: from localhost ([107.15.81.208]) by smtp.gmail.com with ESMTPSA id v9sm9126070ywh.2.2018.12.11.09.38.06 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 11 Dec 2018 09:38:06 -0800 (PST) From: Josef Bacik To: kernel-team@fb.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, tj@kernel.org, david@fromorbit.com, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, riel@redhat.com, jack@suse.cz Subject: [PATCH 1/3] filemap: kill page_cache_read usage in filemap_fault Date: Tue, 11 Dec 2018 12:37:59 -0500 Message-Id: <20181211173801.29535-2-josef@toxicpanda.com> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20181211173801.29535-1-josef@toxicpanda.com> References: <20181211173801.29535-1-josef@toxicpanda.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If we do not have a page at filemap_fault time we'll do this weird forced page_cache_read thing to populate the page, and then drop it again and loop around and find it. This makes for 2 ways we can read a page in filemap_fault, and it's not really needed. Instead add a FGP_FOR_MMAP flag so that pagecache_get_page() will return a unlocked page that's in pagecache. Then use the normal page locking and readpage logic already in filemap_fault. This simplifies the no page in page cache case significantly. Acked-by: Johannes Weiner Reviewed-by: Jan Kara Signed-off-by: Josef Bacik --- include/linux/pagemap.h | 1 + mm/filemap.c | 73 ++++++++++--------------------------------------- 2 files changed, 16 insertions(+), 58 deletions(-) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 226f96f0dee0..b13c2442281f 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -252,6 +252,7 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping, #define FGP_WRITE 0x00000008 #define FGP_NOFS 0x00000010 #define FGP_NOWAIT 0x00000020 +#define FGP_FOR_MMAP 0x00000040 struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, int fgp_flags, gfp_t cache_gfp_mask); diff --git a/mm/filemap.c b/mm/filemap.c index 81adec8ee02c..03bce38d8f2b 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1503,6 +1503,9 @@ EXPORT_SYMBOL(find_lock_entry); * @gfp_mask and added to the page cache and the VM's LRU * list. The page is returned locked and with an increased * refcount. Otherwise, NULL is returned. + * - FGP_FOR_MMAP: Similar to FGP_CREAT, only we want to allow the caller to do + * its own locking dance if the page is already in cache, or unlock the page + * before returning if we had to add the page to pagecache. * * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even * if the GFP flags specified for FGP_CREAT are atomic. @@ -1555,7 +1558,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, if (!page) return NULL; - if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK))) + if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP)))) fgp_flags |= FGP_LOCK; /* Init accessed so avoid atomic mark_page_accessed later */ @@ -1569,6 +1572,13 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, if (err == -EEXIST) goto repeat; } + + /* + * add_to_page_cache_lru lock's the page, and for mmap we expect + * a unlocked page. + */ + if (fgp_flags & FGP_FOR_MMAP) + unlock_page(page); } return page; @@ -2293,39 +2303,6 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) EXPORT_SYMBOL(generic_file_read_iter); #ifdef CONFIG_MMU -/** - * page_cache_read - adds requested page to the page cache if not already there - * @file: file to read - * @offset: page index - * @gfp_mask: memory allocation flags - * - * This adds the requested page to the page cache if it isn't already there, - * and schedules an I/O to read in its contents from disk. - */ -static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask) -{ - struct address_space *mapping = file->f_mapping; - struct page *page; - int ret; - - do { - page = __page_cache_alloc(gfp_mask); - if (!page) - return -ENOMEM; - - ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask); - if (ret == 0) - ret = mapping->a_ops->readpage(file, page); - else if (ret == -EEXIST) - ret = 0; /* losing race to add is OK */ - - put_page(page); - - } while (ret == AOP_TRUNCATED_PAGE); - - return ret; -} - #define MMAP_LOTSAMISS (100) /* @@ -2449,9 +2426,11 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); ret = VM_FAULT_MAJOR; retry_find: - page = find_get_page(mapping, offset); + page = pagecache_get_page(mapping, offset, + FGP_CREAT|FGP_FOR_MMAP, + vmf->gfp_mask); if (!page) - goto no_cached_page; + return vmf_error(-ENOMEM); } if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) { @@ -2488,28 +2467,6 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) vmf->page = page; return ret | VM_FAULT_LOCKED; -no_cached_page: - /* - * We're only likely to ever get here if MADV_RANDOM is in - * effect. - */ - error = page_cache_read(file, offset, vmf->gfp_mask); - - /* - * The page we want has now been added to the page cache. - * In the unlikely event that someone removed it in the - * meantime, we'll just come back here and read it again. - */ - if (error >= 0) - goto retry_find; - - /* - * An error return from page_cache_read can result if the - * system is low on memory, or a problem occurs while trying - * to schedule I/O. - */ - return vmf_error(error); - page_not_uptodate: /* * Umm, take care of errors if the page isn't up-to-date. -- 2.14.3