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From: Andrew Morton <akpm@linux-foundation.org>
To: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch v2] mm, thp: fix defrag setting if newline is not used
Date: Sat, 18 Jan 2020 17:04:45 -0800	[thread overview]
Message-ID: <20200118170445.370d908ce29f42068390addb@linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.2.21.2001171411020.56385@chino.kir.corp.google.com>

On Fri, 17 Jan 2020 14:11:48 -0800 (PST) David Rientjes <rientjes@google.com> wrote:

> If thp defrag setting "defer" is used and a newline is *not* used when
> writing to the sysfs file, this is interpreted as the "defer+madvise"
> option.
> 
> This is because we do prefix matching and if five characters are written
> without a newline, the current code ends up comparing to the first five
> bytes of the "defer+madvise" option and using that instead.
> 
> Use the more appropriate sysfs_streq() that handles the trailing newline
> for us.  Since this doubles as a nice cleanup, do it in enabled_store()
> as well.

I can't really I really understand this prefix-matching thing that
we're taking away.  Documentation/admin-guide/mm/transhuge.rst doesn't
appear to mention it.  Could we please add a paragraph to the changelog
to spell all this out.  Bonus points for formally describing the
behaviour which we're removing!

Thanks.


  parent reply	other threads:[~2020-01-19  1:04 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15  1:58 [patch] mm, thp: fix defrag setting if newline is not used David Rientjes
2020-01-15  1:58 ` David Rientjes
2020-01-15 12:45 ` Vlastimil Babka
2020-01-17  3:16 ` Andrew Morton
2020-01-17  8:24   ` Vlastimil Babka
2020-01-17  9:43     ` David Rientjes
2020-01-17  9:43       ` David Rientjes
2020-01-17 10:12       ` Vlastimil Babka
2020-01-17 22:11         ` [patch v2] " David Rientjes
2020-01-17 22:11           ` David Rientjes
2020-01-18 10:54           ` Vlastimil Babka
2020-01-19  1:04           ` Andrew Morton [this message]
2020-01-19 21:57             ` David Rientjes
2020-01-19 21:57               ` David Rientjes

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