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Message-ID: <20170117172925.GA2486@quack2.suse.cz> Date: Tue, 17 Jan 2017 18:29:25 +0100 From: Jan Kara <jack@...e.cz> To: Michal Hocko <mhocko@...nel.org> Cc: Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.cz>, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Dave Chinner <david@...morbit.com>, djwong@...nel.org, Chris Mason <clm@...com>, David Sterba <dsterba@...e.cz>, ceph-devel@...r.kernel.org, cluster-devel@...hat.com, linux-nfs@...r.kernel.org, logfs@...fs.org, linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org, linux-mtd@...ts.infradead.org, reiserfs-devel@...r.kernel.org, linux-ntfs-dev@...ts.sourceforge.net, linux-f2fs-devel@...ts.sourceforge.net, linux-afs@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 8/8] Revert "ext4: fix wrong gfp type under transaction" On Tue 17-01-17 17:16:19, Michal Hocko wrote: > > > But before going to play with that I am really wondering whether we need > > > all this with no journal at all. AFAIU what Jack told me it is the > > > journal lock(s) which is the biggest problem from the reclaim recursion > > > point of view. What would cause a deadlock in no journal mode? > > > > We still have the original problem for why we need GFP_NOFS even in > > ext2. If we are in a writeback path, and we need to allocate memory, > > we don't want to recurse back into the file system's writeback path. > > But we do not enter the writeback path from the direct reclaim. Or do > you mean something other than pageout()'s mapping->a_ops->writepage? > There is only try_to_release_page where we get back to the filesystems > but I do not see any NOFS protection in ext4_releasepage. Maybe to expand a bit: These days, direct reclaim can call ->releasepage() callback, ->evict_inode() callback (and only for inodes with i_nlink > 0), shrinkers. That's it. So the recursion possibilities are rather more limited than they used to be several years ago and we likely do not need as much GFP_NOFS protection as we used to. Honza -- Jan Kara <jack@...e.com> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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