linux-kernel - Re: [GIT PULL] Please pull NFS client fixes for 4.12

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Date:   Thu, 11 May 2017 15:54:43 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Trond Myklebust <trondmy@...marydata.com>
Cc:     "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "n.borisov.lkml@...il.com" <n.borisov.lkml@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>
Subject: Re: [GIT PULL] Please pull NFS client fixes for 4.12

On Thu 11-05-17 13:41:12, Trond Myklebust wrote:
> On Thu, 2017-05-11 at 10:53 +0300, Nikolay Borisov wrote:
> > 
> > On 10.05.2017 19:47, Trond Myklebust wrote:
> > > Hi Linus,
> > > 
> > > The following changes since commit
> > > 4f7d029b9bf009fbee76bb10c0c4351a1870d2f3:
> > > 
> > >   Linux 4.11-rc7 (2017-04-16 13:00:18 -0700)
> > > 
> > > are available in the git repository at:
> > > 
> > >   git://git.linux-nfs.org/projects/trondmy/linux-nfs.git tags/nfs-
> > > for-4.12-1
> > > 
> > > for you to fetch changes up to
> > > 76b2a303384e1d6299c3a0249f0f0ce2f8f96017:
> > > 
> > >   pNFS/flexfiles: Always attempt to call layoutstats when flexfiles
> > > is enabled (2017-05-09 16:02:57 -0400)
> > > 
> > > ----------------------------------------------------------------
> > > NFS client updates for Linux 4.12
> > > 
> > > Highlights include:
> > > 
> > > Stable bugfixes:
> > > - Fix use after free in write error path
> > > - Use GFP_NOIO for two allocations in writeback
> > > - Fix a hang in OPEN related to server reboot
> > > - Check the result of nfs4_pnfs_ds_connect
> > > - Fix an rcu lock leak
> > > 
> > > Features:
> > > - Removal of the unmaintained and unused OSD pNFS layout
> > > - Cleanup and removal of lots of unnecessary dprintk()s
> > > - Cleanup and removal of some memory failure paths now that
> > >   GFP_NOFS is guaranteed to never fail.
> > 
> > What guarantees that? Since if this is the case then this can result
> > in
> > a lot of opportunities for cleanup across the whole kernel tree.
> > After
> > discussing with mhocko (cc'ed) it seems that in practice everything
> > below COSTLY_ORDER which are not GFP_NORETRY will never fail. But
> > this
> > semantic is not the same as GFP_NOFAIL. E.g. nothing guarantees that
> > this will stay like that in the future?
> > 
> 
> Actually, going back to the code with coffee: it's the fact we have
> mempools, with direct reclaim that guarantee this.

Mempools are a different story, of course. They do the their own loop on
top of the underlying allocator.
-- 
Michal Hocko
SUSE Labs