From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Date: Tue, 16 Jun 2020 19:21:57 -0700 Subject: [Cluster-devel] [PATCH v11 16/25] fs: Convert mpage_readpages to mpage_readahead In-Reply-To: References: <20200414150233.24495-1-willy@infradead.org> <20200414150233.24495-17-willy@infradead.org> <20200617003216.GC8681@bombadil.infradead.org> Message-ID: <20200617022157.GF8681@bombadil.infradead.org> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Wed, Jun 17, 2020 at 02:57:14AM +0200, Andreas Gr??nbacher wrote: > Am Mi., 17. Juni 2020 um 02:33 Uhr schrieb Matthew Wilcox : > > > > On Wed, Jun 17, 2020 at 12:36:13AM +0200, Andreas Gruenbacher wrote: > > > Am Mi., 15. Apr. 2020 um 23:39 Uhr schrieb Matthew Wilcox : > > > > From: "Matthew Wilcox (Oracle)" > > > > > > > > Implement the new readahead aop and convert all callers (block_dev, > > > > exfat, ext2, fat, gfs2, hpfs, isofs, jfs, nilfs2, ocfs2, omfs, qnx6, > > > > reiserfs & udf). The callers are all trivial except for GFS2 & OCFS2. > > > > > > This patch leads to an ABBA deadlock in xfstest generic/095 on gfs2. > > > > > > Our lock hierarchy is such that the inode cluster lock ("inode glock") > > > for an inode needs to be taken before any page locks in that inode's > > > address space. > > > > How does that work for ... > > > > writepage: yes, unlocks (see below) > > readpage: yes, unlocks > > invalidatepage: yes > > releasepage: yes > > freepage: yes > > isolate_page: yes > > migratepage: yes (both) > > putback_page: yes > > launder_page: yes > > is_partially_uptodate: yes > > error_remove_page: yes > > > > Is there a reason that you don't take the glock in the higher level > > ops which are called before readhead gets called? I'm looking at XFS, > > and it takes the xfs_ilock SHARED in xfs_file_buffered_aio_read() > > (called from xfs_file_read_iter). > > Right, the approach from the following thread might fix this: > > https://lore.kernel.org/linux-fsdevel/20191122235324.17245-1-agruenba at redhat.com/T/#t In general, I think this is a sound approach. Specifically, I think FAULT_FLAG_CACHED can go away. map_pages() will bring in the pages which are in the page cache, so when we get to gfs2_fault(), we know there's a reason to acquire the glock.