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From: Andi Kleen <ak@linux.intel.com>
To: Luis Felipe Sandoval Castro <luis.felipe.sandoval.castro@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com,
	mingo@kernel.org, rientjes@google.com, n-horiguchi@ah.jp.nec.com,
	salls@cs.ucsb.edu
Subject: Re: [PATCH v1][cover-letter] mm/mempolicy.c: Fix get_nodes() off-by-one error.
Date: Fri, 06 Oct 2017 15:12:40 -0700	[thread overview]
Message-ID: <87a814ncx3.fsf@linux.intel.com> (raw)
In-Reply-To: <1507296994-175620-1-git-send-email-luis.felipe.sandoval.castro@intel.com> (Luis Felipe Sandoval Castro's message of "Fri, 6 Oct 2017 08:36:33 -0500")

Luis Felipe Sandoval Castro <luis.felipe.sandoval.castro@intel.com>
writes:

> According to mbind() and set_mempolicy()'s man pages the argument "maxnode"
> specifies the max number of bits in the "nodemask" (which is also to be passed
> to these functions) that should be considered for the memory policy. If maxnode
> = 2, only two bits are to be considered thus valid node masks are: 0b00, 0b01,
> 0b10 and 0b11.

We can't change this unfortunately, it would break old binaries (like
libnuma) which assume the old interface.

The only way to fix it would be to add a new system call and keep
the old one for compatibility, but that would seem like overkill just
for this.

You always have to add +1, sorry.

Perhaps it could be better documented.

-Andi

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WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <ak@linux.intel.com>
To: Luis Felipe Sandoval Castro  <luis.felipe.sandoval.castro@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com,
	mingo@kernel.org, rientjes@google.com, n-horiguchi@ah.jp.nec.com,
	salls@cs.ucsb.edu
Subject: Re: [PATCH v1][cover-letter] mm/mempolicy.c: Fix get_nodes() off-by-one error.
Date: Fri, 06 Oct 2017 15:12:40 -0700	[thread overview]
Message-ID: <87a814ncx3.fsf@linux.intel.com> (raw)
In-Reply-To: <1507296994-175620-1-git-send-email-luis.felipe.sandoval.castro@intel.com> (Luis Felipe Sandoval Castro's message of "Fri, 6 Oct 2017 08:36:33 -0500")

Luis Felipe Sandoval Castro <luis.felipe.sandoval.castro@intel.com>
writes:

> According to mbind() and set_mempolicy()'s man pages the argument "maxnode"
> specifies the max number of bits in the "nodemask" (which is also to be passed
> to these functions) that should be considered for the memory policy. If maxnode
> = 2, only two bits are to be considered thus valid node masks are: 0b00, 0b01,
> 0b10 and 0b11.

We can't change this unfortunately, it would break old binaries (like
libnuma) which assume the old interface.

The only way to fix it would be to add a new system call and keep
the old one for compatibility, but that would seem like overkill just
for this.

You always have to add +1, sorry.

Perhaps it could be better documented.

-Andi

  parent reply	other threads:[~2017-10-06 22:12 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-06 13:36 [PATCH v1][cover-letter] mm/mempolicy.c: Fix get_nodes() off-by-one error Luis Felipe Sandoval Castro
2017-10-06 13:36 ` Luis Felipe Sandoval Castro
2017-10-06 13:36 ` [PATCH v1] " Luis Felipe Sandoval Castro
2017-10-06 13:36   ` Luis Felipe Sandoval Castro
2017-10-12  8:46   ` Michal Hocko
2017-10-12  8:46     ` Michal Hocko
2017-10-12  9:14     ` Vlastimil Babka
2017-10-12  9:14       ` Vlastimil Babka
2017-10-12  9:29       ` Michal Hocko
2017-10-12  9:29         ` Michal Hocko
2017-10-12 15:28     ` Andi Kleen
2017-10-12 15:28       ` Andi Kleen
2017-10-13  8:04       ` Michal Hocko
2017-10-13  8:04         ` Michal Hocko
2017-10-19  3:48         ` Sandoval Castro, Luis Felipe
2017-10-19  3:48           ` Sandoval Castro, Luis Felipe
2017-10-19  4:28           ` Andi Kleen
2017-10-19  4:28             ` Andi Kleen
2017-10-06 22:12 ` Andi Kleen [this message]
2017-10-06 22:12   ` [PATCH v1][cover-letter] " Andi Kleen

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