From mboxrd@z Thu Jan 1 00:00:00 1970 From: Darrick J. Wong Date: Tue, 30 Apr 2019 08:47:07 -0700 Subject: [Cluster-devel] [PATCH v7 5/5] gfs2: Fix iomap write page reclaim deadlock In-Reply-To: References: <20190429220934.10415-1-agruenba@redhat.com> <20190429220934.10415-6-agruenba@redhat.com> <20190430153256.GF5200@magnolia> Message-ID: <20190430154707.GG5200@magnolia> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Tue, Apr 30, 2019 at 05:39:28PM +0200, Andreas Gruenbacher wrote: > On Tue, 30 Apr 2019 at 17:33, Darrick J. Wong wrote: > > On Tue, Apr 30, 2019 at 12:09:34AM +0200, Andreas Gruenbacher wrote: > > > Since commit 64bc06bb32ee ("gfs2: iomap buffered write support"), gfs2 is doing > > > buffered writes by starting a transaction in iomap_begin, writing a range of > > > pages, and ending that transaction in iomap_end. This approach suffers from > > > two problems: > > > > > > (1) Any allocations necessary for the write are done in iomap_begin, so when > > > the data aren't journaled, there is no need for keeping the transaction open > > > until iomap_end. > > > > > > (2) Transactions keep the gfs2 log flush lock held. When > > > iomap_file_buffered_write calls balance_dirty_pages, this can end up calling > > > gfs2_write_inode, which will try to flush the log. This requires taking the > > > log flush lock which is already held, resulting in a deadlock. > > > > /me wonders how holding the log flush lock doesn't seriously limit > > performance, but gfs2 isn't my fight so I'll set that aside and assume > > that a patch S-o-B'd by both maintainers is ok. :) > > This only affects inline and journaled data, not standard writes, so > it's not quite as bad as it looks. Ah, ok. > > How should we merge this patch #5? It doesn't touch fs/iomap.c itself, > > so do you want me to pull it into the iomap branch along with the > > previous four patches? That would be fine with me (and easier than a > > multi-tree merge mess)... > > I'd prefer to get this merged via the gfs2 tree once the iomap fixes > have been pulled. Ok, I'll take the first four patches through the iomap branch and cc you on the pull request. --D > > Thanks, > Andreas