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From: NeilBrown <neilb@suse.com>
To: Vlastimil Babka <vbabka@suse.cz>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>
Cc: Linux-Next Mailing List <linux-next@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Michal Hocko <mhocko@kernel.org>
Subject: Re: linux-next: manual merge of the akpm-current tree with the tip tree
Date: Thu, 20 Apr 2017 12:17:19 +1000
Message-ID: <87pog7stzk.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <bd7abc05-da24-8c65-c93e-ec30fe582233@suse.cz>

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On Wed, Apr 12 2017, Vlastimil Babka wrote:

> On 12.4.2017 8:46, Stephen Rothwell wrote:
>> Hi Andrew,
>> 
>> Today's linux-next merge of the akpm-current tree got conflicts in:
>> 
>>   drivers/block/nbd.c
>>   drivers/scsi/iscsi_tcp.c
>>   net/core/dev.c
>>   net/core/sock.c
>> 
>> between commit:
>> 
>>   717a94b5fc70 ("sched/core: Remove 'task' parameter and rename tsk_restore_flags() to current_restore_flags()")
>> 
>> from the tip tree and commit:
>> 
>>   61d5ad5b2e8a ("treewide: convert PF_MEMALLOC manipulations to new helpers")
>> 
>> from the akpm-current tree.
>
> Yeah, the first patch from Neil renames a function (as its subject says) and the
> second patch from me converts most of its users to new helpers specific to the
> PF_MEMALLOC flags.
>
>> I fixed it up (the latter is just a superset of the former, so I used
>
> It's not a complete superset though, more on that below.
>
>> that) and can carry the fix as necessary. This is now fixed as far as
>> linux-next is concerned, but any non trivial conflicts should be mentioned
>> to your upstream maintainer when your tree is submitted for merging.
>> You may also want to consider cooperating with the maintainer of the
>> conflicting tree to minimise any particularly complex conflicts.
>
> Hmm I could redo my patch on top of Neil's patch, but then Andrew would have to
> carry Neil's patch as well just to have a working mmotm? And then make sure to
> send my patch (but not Neil's) only after the tip tree is pulled? Would that
> work for the maintainers involved?
>
>> It looks like there may be more instances that the latter patch should
>> update.
>
> I see two remaining instances of current_restore_flags(). One in __do_softirq()
> is even for PF_MEMALLOC, but there the flag is cleared first and then set back,
> which is opposite of the common case that my helpers provide. The other in nfsd
> is for PF_LESS_THROTTLE which is not common enough to earn own helpers yet. IIRC
> Neil originally wanted to add a new one?

[Sorry - I thought I had sent this last week, but just noticed that I didn't]

In general, I'm not a fan of overly-specific helpers.

As a general rule, tsk_restore_flags() is probably better than
current_restore_flags() as it is more general.
However in this specific case, using any task other than 'current' would
almost certainly be incorrect code as locking is impossible.  So I
prefer the 'current' to be implicit, but the actual flag to be explicit.

If you are going to add helpers for setting/clearing PF flags, I would
much rather that you take

#define current_test_flags(f)   (current->flags & (f))
#define current_set_flags_nested(sp, f)         \
                (*(sp) = current->flags, current->flags |= (f))
#define current_clear_flags_nested(sp, f)       \
                (*(sp) = current->flags, current->flags &= ~(f))
#define current_restore_flags_nested(sp, f)     \
                (current->flags = ((current->flags & ~(f)) | (*(sp) & (f))))

out of fs/xfs/xfs_linux.h and use them globally.

Your
  noreclaim_flag = memalloc_reclaim_save()
becomes
  current_set_flags_nested&noreclaim_flag, PF_MEMALLOC)
which is more typing, but arguably easier to read.

If you then changed all uses of tsk_restore_flags() to use
current_restore_flags_nested(), my patch could be discarded as
irrelevant.

Thanks,
NeilBrown

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  reply index

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-12  6:46 Stephen Rothwell
2017-04-12 20:53 ` Vlastimil Babka
2017-04-20  2:17   ` NeilBrown [this message]
  -- strict thread matches above, loose matches on Subject: below --
2019-10-31  5:43 Stephen Rothwell
2019-06-24 10:24 Stephen Rothwell
2019-05-01 11:10 Stephen Rothwell
2019-01-31  4:31 Stephen Rothwell
2018-08-20  4:32 Stephen Rothwell
2018-08-20 19:52 ` Andrew Morton
2018-03-23  5:59 Stephen Rothwell
2017-12-18  5:04 Stephen Rothwell
2017-11-10  4:33 Stephen Rothwell
2017-11-02  7:19 Stephen Rothwell
2017-08-22  6:57 Stephen Rothwell
2017-08-23  6:39 ` Vlastimil Babka
2017-08-11  7:53 Stephen Rothwell
2017-08-11  9:34 ` Peter Zijlstra
2017-08-11 10:48   ` Peter Zijlstra
2017-08-11 11:45   ` Stephen Rothwell
2017-08-11 11:56     ` Ingo Molnar
2017-08-11 12:17       ` Peter Zijlstra
2017-08-11 12:44         ` Ingo Molnar
2017-08-11 13:49           ` Stephen Rothwell
2017-08-11 14:04       ` Peter Zijlstra
2017-08-13  6:06         ` Nadav Amit
2017-08-13 12:50           ` Peter Zijlstra
2017-08-14  3:16             ` Minchan Kim
2017-08-14  5:07               ` Nadav Amit
2017-08-14  5:23                 ` Minchan Kim
2017-08-14  8:38                 ` Minchan Kim
2017-08-14 19:57                   ` Peter Zijlstra
2017-08-16  4:14                     ` Minchan Kim
2017-08-14 19:38                 ` Peter Zijlstra
2017-08-15  7:51                   ` Nadav Amit
2017-08-14  3:09         ` Minchan Kim
2017-08-14 18:54           ` Peter Zijlstra
2017-03-24  5:25 Stephen Rothwell
2017-02-17  4:40 Stephen Rothwell
2016-11-14  6:08 Stephen Rothwell
2016-07-29  4:14 Stephen Rothwell
2016-06-15  5:23 Stephen Rothwell
2016-06-18 19:39 ` Manfred Spraul
2016-04-29  6:12 Stephen Rothwell
2016-04-29  6:26 ` Ingo Molnar
2016-03-02  5:40 Stephen Rothwell
2016-02-26  5:07 Stephen Rothwell
2016-02-26 21:35 ` Andrew Morton
2016-02-19  4:09 Stephen Rothwell
2016-02-19 15:26 ` Ard Biesheuvel
2015-12-07  8:06 Stephen Rothwell
2015-10-02  4:21 Stephen Rothwell
2015-07-28  6:00 Stephen Rothwell
2015-07-29 17:12 ` Andrea Arcangeli
2015-07-29 17:47   ` Andy Lutomirski
2015-07-29 18:46     ` Thomas Gleixner
2015-07-30 15:38       ` Andrea Arcangeli
2015-07-29 23:06   ` Stephen Rothwell
2015-07-29 23:07     ` Thomas Gleixner
2015-09-07 23:35   ` Stephen Rothwell
2015-09-08 18:11     ` Linus Torvalds
2015-09-08 22:56       ` Stephen Rothwell
2015-09-08 23:03         ` Linus Torvalds
2015-09-08 23:21           ` Andrew Morton
2015-09-16  6:58             ` Geert Uytterhoeven
2015-06-04 12:07 Stephen Rothwell
2015-04-08  8:28 Stephen Rothwell
2015-04-08  8:25 Stephen Rothwell
2014-03-17  9:31 Stephen Rothwell
2014-03-17  9:36 ` Peter Zijlstra
2014-03-19 23:27   ` Andrew Morton
2014-01-14  4:53 Stephen Rothwell
2014-01-14  5:04 ` Davidlohr Bueso
2014-01-14 12:51 ` Peter Zijlstra
2014-01-14 13:17   ` Geert Uytterhoeven
2014-01-14 13:33     ` Peter Zijlstra
2014-01-14 16:19     ` H. Peter Anvin
2014-01-14 15:15   ` H. Peter Anvin
2014-01-14 15:20     ` Geert Uytterhoeven
2014-01-14 15:41       ` Peter Zijlstra
2014-01-14 15:48         ` H. Peter Anvin
2014-01-07  6:00 Stephen Rothwell
2014-01-07  6:34 ` Tang Chen
2013-11-08  7:48 Stephen Rothwell
2013-11-08 18:58 ` Josh Triplett
2013-11-08 23:20   ` Stephen Rothwell
2013-11-09  0:19     ` Josh Triplett
2013-10-30  6:40 Stephen Rothwell

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