From: Andrew Morton <akpm@linux-foundation.org>
To: Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
Cc: mhocko@suse.com, oleg@redhat.com, cmetcalf@ezchip.com,
mszeredi@suse.cz, viro@zeniv.linux.org.uk, dave@stgolabs.net,
kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com,
aarcange@redhat.com, iamjoonsoo.kim@lge.com, jack@suse.cz,
xiexiuqi@huawei.com, vbabka@suse.cz, Vineet.Gupta1@synopsys.com,
riel@redhat.com, gang.chen.5i5j@gmail.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v3] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region
Date: Mon, 23 Nov 2015 14:14:01 -0800 [thread overview]
Message-ID: <20151123141401.0ad7e291be4d62ec83de7101@linux-foundation.org> (raw)
In-Reply-To: <1448300202-5004-1-git-send-email-kwapulinski.piotr@gmail.com>
On Mon, 23 Nov 2015 18:36:42 +0100 Piotr Kwapulinski <kwapulinski.piotr@gmail.com> wrote:
> The following flag comparison in mmap_region makes no sense:
>
> if (!(vm_flags & MAP_FIXED))
> return -ENOMEM;
>
> The condition is always false and thus the above "return -ENOMEM" is never
> executed. The vm_flags must not be compared with MAP_FIXED flag.
> The vm_flags may only be compared with VM_* flags.
> MAP_FIXED has the same value as VM_MAYREAD.
> Hitting the rlimit is a slow path and find_vma_intersection should realize
> that there is no overlapping VMA for !MAP_FIXED case pretty quickly.
>
> Remove the code that makes no sense.
>
> ...
>
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1551,9 +1551,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> * MAP_FIXED may remove pages of mappings that intersects with
> * requested mapping. Account for the pages it would unmap.
> */
> - if (!(vm_flags & MAP_FIXED))
> - return -ENOMEM;
> -
> nr_pages = count_vma_pages_range(mm, addr, addr + len);
>
> if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))
Did you intend to retain the stale comment?
next prev parent reply other threads:[~2015-11-23 22:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-16 17:36 [PATCH] mm: fix incorrect behavior when process virtual address space limit is exceeded Piotr Kwapulinski
2015-11-16 20:52 ` Michal Hocko
2015-11-17 0:33 ` Michal Hocko
2015-11-18 14:32 ` Cyril Hrubis
2015-11-17 16:19 ` Oleg Nesterov
2015-11-17 16:33 ` Oleg Nesterov
2015-11-17 17:26 ` [PATCH] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region Piotr Kwapulinski
2015-11-18 0:52 ` Andrew Morton
2015-11-18 16:29 ` Piotr Kwapulinski
2015-11-20 16:38 ` [PATCH v2 1/2] mm: fix incorrect behavior when process virtual address space limit is exceeded Piotr Kwapulinski
2015-11-20 16:42 ` [PATCH v2 2/2] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region Piotr Kwapulinski
2015-11-23 8:19 ` Michal Hocko
2015-11-23 17:36 ` [PATCH v3] " Piotr Kwapulinski
2015-11-23 22:14 ` Andrew Morton [this message]
2015-11-24 16:12 ` Piotr Kwapulinski
2015-11-27 5:27 ` Naoya Horiguchi
2015-11-17 17:38 ` [PATCH] mm: fix incorrect behavior when process virtual address space limit is exceeded Chris Metcalf
2015-11-17 19:03 ` Oleg Nesterov
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