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=-9.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9F160C433E2 for ; Sat, 12 Sep 2020 03:20:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9D06B2083E for ; Sat, 12 Sep 2020 03:20:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="POSXWmPe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D06B2083E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AD8596B0055; Fri, 11 Sep 2020 23:20:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A88CD6B005A; Fri, 11 Sep 2020 23:20:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 99ED56B005C; Fri, 11 Sep 2020 23:20:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0204.hostedemail.com [216.40.44.204]) by kanga.kvack.org (Postfix) with ESMTP id 804006B0055 for ; Fri, 11 Sep 2020 23:20:54 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 38DD93630 for ; Sat, 12 Sep 2020 03:20:54 +0000 (UTC) X-FDA: 77252957628.10.cause24_3309144270f4 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin10.hostedemail.com (Postfix) with ESMTP id 0DF1A16A0DE for ; Sat, 12 Sep 2020 03:20:54 +0000 (UTC) X-HE-Tag: cause24_3309144270f4 X-Filterd-Recvd-Size: 6985 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf43.hostedemail.com (Postfix) with ESMTP for ; Sat, 12 Sep 2020 03:20:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3XyNqMnXE3dOK2LZAXqfj7lb32o+C6Csf8Brn5Bb450=; b=POSXWmPe4sISzgZQH+wc1kFuN3 zmQW6gC6mLwro2U2FtHW7Sq93S+VHIBsct6sWrOaNPkyAQFzzqNf8xvDFwDMjm9G5OBLpip/L2MCw 2hgEDnwZb400PZWOBSnVpoQJXOd33tlbN5YkfZGu7uS9j2nvE7pEH4Zr6Eg0MhTouPNg+RPUrpqXd rPj6X2GCPbfbcGJ7tF3ijPy4hbLotRMAy/KayY7tFS0lna10TRTjm1hPkjAVjVF4clTnF+G0+t5Ua DN0oTTARMku5+xwm3lRWb1U1vQmFiBoUDSzwq1nbBeRykblqL6AYaT3brtZD134pn2pzNW7IjXeDe RAIxAAgQ==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kGw5i-0006YH-Ck; Sat, 12 Sep 2020 03:20:42 +0000 Date: Sat, 12 Sep 2020 04:20:42 +0100 From: Matthew Wilcox To: linux-mm@kvack.org Cc: Andrew Morton , Hugh Dickins , William Kucharski , Jani Nikula , Alexey Dobriyan , Johannes Weiner , Chris Wilson , Matthew Auld , Huang Ying , intel-gfx@lists.freedesktop.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 7/8] mm/shmem: Return head page from find_lock_entry Message-ID: <20200912032042.GA6583@casper.infradead.org> References: <20200910183318.20139-1-willy@infradead.org> <20200910183318.20139-8-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200910183318.20139-8-willy@infradead.org> X-Rspamd-Queue-Id: 0DF1A16A0DE X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: On Thu, Sep 10, 2020 at 07:33:17PM +0100, Matthew Wilcox (Oracle) wrote: > Convert shmem_getpage_gfp() (the only remaining caller of > find_lock_entry()) to cope with a head page being returned instead of > the subpage for the index. This version was buggy. Apparently I was too focused on running the test suite against XFS and neglected to run it against tmpfs, which crashed instantly. Here's the patch I should have sent. commit 7bfa655881da76f3386e6d4c07e38a165b4a6ca8 Author: Matthew Wilcox (Oracle) Date: Sun Aug 2 07:22:34 2020 -0400 mm/shmem: Return head page from find_lock_entry Convert shmem_getpage_gfp() (the only remaining caller of find_lock_entry()) to cope with a head page being returned instead of the subpage for the index. Signed-off-by: Matthew Wilcox (Oracle) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 905a64030647..f374618b2c93 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -371,6 +371,15 @@ static inline struct page *grab_cache_page_nowait(struct address_space *mapping, mapping_gfp_mask(mapping)); } +/* Does this page contain this index? */ +static inline bool thp_contains(struct page *head, pgoff_t index) +{ + /* HugeTLBfs indexes the page cache in units of hpage_size */ + if (PageHuge(head)) + return head->index == index; + return page_index(head) == (index & ~(thp_nr_pages(head) - 1UL)); +} + /* * Given the page we found in the page cache, return the page corresponding * to this index in the file diff --git a/mm/filemap.c b/mm/filemap.c index 2f134383b0ae..453535170b8d 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1614,37 +1614,34 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t index) } /** - * find_lock_entry - locate, pin and lock a page cache entry - * @mapping: the address_space to search - * @offset: the page cache index + * find_lock_entry - Locate and lock a page cache entry. + * @mapping: The address_space to search. + * @index: The page cache index. * - * Looks up the page cache slot at @mapping & @offset. If there is a - * page cache page, it is returned locked and with an increased - * refcount. + * Looks up the page at @mapping & @index. If there is a page in the + * cache, the head page is returned locked and with an increased refcount. * * If the slot holds a shadow entry of a previously evicted page, or a * swap entry from shmem/tmpfs, it is returned. * - * find_lock_entry() may sleep. - * - * Return: the found page or shadow entry, %NULL if nothing is found. + * Context: May sleep. + * Return: The head page or shadow entry, %NULL if nothing is found. */ -struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset) +struct page *find_lock_entry(struct address_space *mapping, pgoff_t index) { struct page *page; repeat: - page = find_get_entry(mapping, offset); + page = find_get_entry(mapping, index); if (page && !xa_is_value(page)) { lock_page(page); /* Has the page been truncated? */ - if (unlikely(page_mapping(page) != mapping)) { + if (unlikely(page->mapping != mapping)) { unlock_page(page); put_page(page); goto repeat; } - page = find_subpage(page, offset); - VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page); + VM_BUG_ON_PAGE(!thp_contains(page, index), page); } return page; } diff --git a/mm/shmem.c b/mm/shmem.c index 271548ca20f3..58bc9e326d0d 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1822,6 +1822,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, return error; } + if (page) + hindex = page->index; if (page && sgp == SGP_WRITE) mark_page_accessed(page); @@ -1832,11 +1834,10 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, unlock_page(page); put_page(page); page = NULL; + hindex = index; } - if (page || sgp == SGP_READ) { - *pagep = page; - return 0; - } + if (page || sgp == SGP_READ) + goto out; /* * Fast cache lookup did not find it: @@ -1961,14 +1962,13 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, * it now, lest undo on failure cancel our earlier guarantee. */ if (sgp != SGP_WRITE && !PageUptodate(page)) { - struct page *head = compound_head(page); int i; - for (i = 0; i < compound_nr(head); i++) { - clear_highpage(head + i); - flush_dcache_page(head + i); + for (i = 0; i < compound_nr(page); i++) { + clear_highpage(page + i); + flush_dcache_page(page + i); } - SetPageUptodate(head); + SetPageUptodate(page); } /* Perhaps the file has been truncated since we checked */ @@ -1984,6 +1984,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, error = -EINVAL; goto unlock; } +out: *pagep = page + index - hindex; return 0;