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From: Michal Hocko <mhocko@kernel.org>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	David Miller <davem@davemloft.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, eric.dumazet@gmail.com, edumazet@google.com,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	mst@redhat.com, jasowang@redhat.com,
	virtualization@lists.linux-foundation.org, dm-devel@redhat.com,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM
Date: Tue, 24 Apr 2018 07:31:46 -0600	[thread overview]
Message-ID: <20180424133146.GG17484@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.LRH.2.02.1804232006540.2299@file01.intranet.prod.int.rdu2.redhat.com>

On Mon 23-04-18 20:25:15, Mikulas Patocka wrote:
> 
> 
> On Mon, 23 Apr 2018, Michal Hocko wrote:
> 
> > On Mon 23-04-18 10:06:08, Mikulas Patocka wrote:
> > 
> > > > > He didn't want to fix vmalloc(GFP_NOIO)
> > > > 
> > > > I don't remember that conversation, so I don't know whether I agree with
> > > > his reasoning or not.  But we are supposed to be moving away from GFP_NOIO
> > > > towards marking regions with memalloc_noio_save() / restore.  If you do
> > > > that, you won't need vmalloc(GFP_NOIO).
> > > 
> > > He said the same thing a year ago. And there was small progress. 6 out of 
> > > 27 __vmalloc calls were converted to memalloc_noio_save in a year - 5 in 
> > > infiniband and 1 in btrfs. (the whole discussion is here 
> > > http://lkml.iu.edu/hypermail/linux/kernel/1706.3/04681.html )
> > 
> > Well this is not that easy. It requires a cooperation from maintainers.
> > I can only do as much. I've posted patches in the past and actively
> > bringing up this topic at LSFMM last two years...
> 
> You're right - but you have chosen the uneasy path.

Yes.

> Fixing __vmalloc code 
> is easy and it doesn't require cooperation with maintainers.

But it is a hack against the intention of the scope api. It also alows
maintainers to not care about their broken code.

> > > He refuses 15-line patch to fix GFP_NOIO bug because he believes that in 4 
> > > years, the kernel will be refactored and GFP_NOIO will be eliminated. Why 
> > > does he have veto over this part of the code? I'd much rather argue with 
> > > people who have constructive comments about fixing bugs than with him.
> > 
> > I didn't NACK the patch AFAIR. I've said it is not a good idea longterm.
> > I would be much more willing to change my mind if you would back your
> > patch by a real bug report. Hacks are acceptable when we have a real
> > issue in hands. But if we want to fix potential issue then better make
> > it properly.
> 
> Developers should fix bugs in advance, not to wait until a crash hapens, 
> is analyzed and reported.

I agree. But are those existing users broken in the first place? I have
seen so many GFP_NOFS abuses that I would dare to guess that most of
those vmalloc NOFS abusers can be simply turned into GFP_KERNEL. Maybe
that is the reason we haven't heard any complains in years.

-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2018-04-24 13:31 UTC|newest]

Thread overview: 110+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-18 14:34 [PATCH] net: don't use kvzalloc for DMA memory Mikulas Patocka
2018-04-18 16:05 ` Eric Dumazet
2018-04-18 16:44   ` Mikulas Patocka
2018-04-18 16:51     ` Eric Dumazet
2018-04-18 17:47       ` David Miller
2018-04-18 17:55         ` Mikulas Patocka
2018-04-18 18:00         ` Michael S. Tsirkin
2018-04-18 17:49       ` Mikulas Patocka
2018-04-18 17:46     ` David Miller
2018-04-18 17:53       ` Mikulas Patocka
2018-04-19 16:12         ` [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM Mikulas Patocka
2018-04-19 16:25           ` Eric Dumazet
2018-04-19 16:28             ` Mikulas Patocka
2018-04-19 16:43           ` Michael S. Tsirkin
2018-04-19 21:27             ` [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG Mikulas Patocka
2018-04-19 18:28           ` [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM Vlastimil Babka
2018-04-19 19:47           ` Andrew Morton
2018-04-19 21:19             ` Mikulas Patocka
2018-04-19 23:22               ` Andrew Morton
2018-04-20 12:16                 ` Mikulas Patocka
2018-04-20 11:47           ` Matthew Wilcox
2018-04-20 12:20             ` Mikulas Patocka
2018-04-23 15:25               ` Michael S. Tsirkin
2018-04-20 13:08           ` Michal Hocko
2018-04-20 13:41             ` Matthew Wilcox
2018-04-20 13:49               ` Michal Hocko
2018-04-20 20:56                 ` Mikulas Patocka
2018-04-20 20:54             ` Mikulas Patocka
2018-04-20 21:02               ` Matthew Wilcox
2018-04-20 21:21                 ` Mikulas Patocka
2018-04-21 14:47                   ` Matthew Wilcox
2018-04-22 13:03                     ` Michal Hocko
2018-04-23 14:24                       ` Mikulas Patocka
2018-04-23 15:10                         ` Michal Hocko
2018-04-23 23:20                           ` Mikulas Patocka
2018-04-23 14:06                     ` Mikulas Patocka
2018-04-23 15:15                       ` Michal Hocko
2018-04-24  0:06                         ` [PATCH v3] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG Mikulas Patocka
2018-04-24  2:47                           ` David Rientjes
2018-04-24 11:04                             ` Mikulas Patocka
2018-04-24  3:46                           ` Matthew Wilcox
2018-04-24 12:29                             ` Mikulas Patocka
2018-04-24 17:16                               ` Matthew Wilcox
2018-04-24 18:41                                 ` Mikulas Patocka
2018-05-15  1:13                                   ` Joonsoo Kim
2018-04-24 12:51                           ` Michal Hocko
2018-04-24 15:50                             ` Mikulas Patocka
2018-04-24 16:29                               ` Michal Hocko
2018-04-24 17:00                                 ` Mikulas Patocka
2018-04-24 17:03                                   ` Michal Hocko
2018-04-24 17:28                                     ` Mikulas Patocka
2018-04-24 17:38                                       ` Michal Hocko
2018-04-25 20:02                                         ` [PATCH] fault-injection: reorder config entries Mikulas Patocka
2018-04-26  3:21                                           ` Randy Dunlap
2018-04-25 20:02                                         ` [PATCH v4] fault-injection: introduce kvmalloc fallback options Mikulas Patocka
2018-04-25 20:20                                           ` Randy Dunlap
2018-04-25 20:57                                             ` [PATCH v5] " Mikulas Patocka
2018-04-25 21:11                                               ` Randy Dunlap
2018-04-25 21:18                                               ` David Rientjes
2018-04-25 21:22                                                 ` Mikulas Patocka
2018-04-25 22:17                                                   ` [dm-devel] " James Bottomley
2018-04-25 22:42                                                     ` Mikulas Patocka
2018-04-25 22:49                                                       ` David Rientjes
2018-04-25 22:56                                                         ` Mikulas Patocka
2018-04-26 12:58                                                       ` Michal Hocko
2018-04-26 14:28                                                         ` Mikulas Patocka
2018-04-26 14:45                                                           ` James Bottomley
2018-04-26 15:05                                                             ` Mikulas Patocka
2018-04-26 15:24                                                               ` James Bottomley
2018-04-26 15:44                                                                 ` Mikulas Patocka
2018-04-26 15:59                                                                   ` Michael S. Tsirkin
2018-04-26 16:07                                                                     ` Mikulas Patocka
2018-04-26 18:49                                                                       ` Michael S. Tsirkin
2018-04-26 18:54                                                                         ` Mikulas Patocka
2018-04-26 19:14                                                                           ` Michael S. Tsirkin
2018-04-26 19:36                                                                             ` Mikulas Patocka
2018-04-26 19:45                                                                               ` Michael S. Tsirkin
2018-04-26 20:05                                                                                 ` Mikulas Patocka
2018-04-26 18:58                                                                     ` Mikulas Patocka
2018-04-26 19:05                                                                       ` Michael S. Tsirkin
2018-04-26 15:55                                                                 ` Mikulas Patocka
2018-04-25 23:00                                                     ` Mikulas Patocka
2018-04-25 23:08                                                       ` James Bottomley
2018-04-26 14:55                                                         ` Mikulas Patocka
2018-04-26 15:22                                                           ` Mikulas Patocka
2018-04-26 18:58                                                         ` John Stoffel
2018-04-26 21:50                                                           ` Mikulas Patocka
2018-04-26 22:21                                                             ` Michael S. Tsirkin
2018-04-26 22:52                                                               ` Mikulas Patocka
2018-04-27  8:25                                                                 ` Michal Hocko
2018-04-27 10:20                                                                   ` Mikulas Patocka
2018-04-27 23:20                                                               ` Mikulas Patocka
2018-04-30 18:27                                                             ` John Stoffel
2018-04-30 21:07                                                               ` Mikulas Patocka
2018-05-02 13:38                                                                 ` John Stoffel
2018-05-03 17:40                                                                   ` Mikulas Patocka
2018-04-24  0:25                         ` [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM Mikulas Patocka
2018-04-24 13:31                           ` Michal Hocko [this message]
2018-04-24 15:30                             ` Mikulas Patocka
2018-04-24 16:12                               ` Michal Hocko
2018-04-24 16:29                                 ` Michal Hocko
2018-04-24 16:33                                 ` Mikulas Patocka
2018-05-02  0:36                                   ` Andrew Morton
2018-05-02 13:33                                     ` Mike Snitzer
2018-05-02 13:40                                       ` [dm-devel] " John Stoffel
2018-05-03 17:32                                     ` [PATCH] " Mikulas Patocka
2018-04-18 17:45   ` [PATCH] net: don't use kvzalloc for DMA memory David Miller
2018-04-18 17:55   ` Michael S. Tsirkin
2018-04-18 20:38     ` Eric Dumazet
2018-04-19  4:00       ` Michael S. Tsirkin

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