From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:37997 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751509AbdAKSr7 (ORCPT ); Wed, 11 Jan 2017 13:47:59 -0500 Date: Wed, 11 Jan 2017 10:47:46 -0800 From: "Darrick J. Wong" Subject: Re: [PATCH v2] xfs: Timely free truncated dirty pages Message-ID: <20170111184746.GV14038@birch.djwong.org> References: <20170111090019.16837-1-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170111090019.16837-1-jack@suse.cz> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Jan Kara Cc: linux-xfs@vger.kernel.org, Petr Tuma , stable@vger.kernel.org, Brian Foster , Vlastimil Babka On Wed, Jan 11, 2017 at 10:00:19AM +0100, Jan Kara wrote: > Commit 99579ccec4e2 "xfs: skip dirty pages in ->releasepage()" started > to skip dirty pages in xfs_vm_releasepage() which also has the effect > that if a dirty page is truncated, it does not get freed by > block_invalidatepage() and is lingering in LRU list waiting for reclaim. > So a simple loop like: > > while true; do > dd if=/dev/zero of=file bs=1M count=100 > rm file > done > > will keep using more and more memory until we hit low watermarks and > start pagecache reclaim which will eventually reclaim also the truncate > pages. Keeping these truncated (and thus never usable) pages in memory > is just a waste of memory, is unnecessarily stressing page cache > reclaim, and reportedly also leads to anonymous mmap(2) returning ENOMEM > prematurely. > > So instead of just skipping dirty pages in xfs_vm_releasepage(), return > to old behavior of skipping them only if they have delalloc or unwritten > buffers and fix the spurious warnings by warning only if the page is > clean. > > CC: stable@vger.kernel.org > CC: Brian Foster > CC: Vlastimil Babka > Reported-by: Petr Tůma > Fixes: 99579ccec4e271c3d4d4e7c946058766812afdab > Signed-off-by: Jan Kara Applied, thanks. --D > --- > fs/xfs/xfs_aops.c | 19 +++++++++++-------- > 1 file changed, 11 insertions(+), 8 deletions(-) > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 0f56fcd3a5d5..631e7c0e0a29 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -1152,19 +1152,22 @@ xfs_vm_releasepage( > * block_invalidatepage() can send pages that are still marked dirty > * but otherwise have invalidated buffers. > * > - * We've historically freed buffers on the latter. Instead, quietly > - * filter out all dirty pages to avoid spurious buffer state warnings. > - * This can likely be removed once shrink_active_list() is fixed. > + * We want to release the latter to avoid unnecessary buildup of the > + * LRU, skip the former and warn if we've left any lingering > + * delalloc/unwritten buffers on clean pages. Skip pages with delalloc > + * or unwritten buffers and warn if the page is not dirty. Otherwise > + * try to release the buffers. > */ > - if (PageDirty(page)) > - return 0; > - > xfs_count_page_state(page, &delalloc, &unwritten); > > - if (WARN_ON_ONCE(delalloc)) > + if (delalloc) { > + WARN_ON_ONCE(!PageDirty(page)); > return 0; > - if (WARN_ON_ONCE(unwritten)) > + } > + if (unwritten) { > + WARN_ON_ONCE(!PageDirty(page)); > return 0; > + } > > return try_to_free_buffers(page); > } > -- > 2.10.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html