From: Oleg Nesterov <oleg@redhat.com>
To: Colin Cross <ccross@android.com>
Cc: linux-kernel@vger.kernel.org,
Kyungmin Park <kmpark@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
John Stultz <john.stultz@linaro.org>,
Rob Landley <rob@landley.net>, Arnd Bergmann <arnd@arndb.de>,
Andrew Morton <akpm@linux-foundation.org>,
Cyrill Gorcunov <gorcunov@openvz.org>,
David Rientjes <rientjes@google.com>,
Davidlohr Bueso <dave@gnu.org>, Kees Cook <keescook@chromium.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>,
Michel Lespinasse <walken@google.com>,
Rik van Riel <riel@redhat.com>,
Konstantin Khlebnikov <khlebnikov@openvz.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Rusty Russell <rusty@rustcorp.com.au>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Michal Hocko <mhocko@suse.cz>,
Anton Vorontsov <anton.vorontsov@linaro.org>,
Pekka Enberg <penberg@kernel.org>, Shaohua Li <shli@fusionio.com>,
Sasha Levin <sasha.levin@oracle.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Ingo Molnar <mingo@kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
"open list:GENERIC INCLUDE/A..." <linux-arch@vger.kernel.org>
Subject: Re: [PATCH] mm: add sys_madvise2 and MADV_NAME to name vmas
Date: Thu, 4 Jul 2013 22:22:32 +0200 [thread overview]
Message-ID: <20130704202232.GA19287@redhat.com> (raw)
In-Reply-To: <1372901537-31033-1-git-send-email-ccross@android.com>
On 07/03, Colin Cross wrote:
>
> The names of named anonymous vmas are shown in /proc/pid/maps
> as [anon:<name>]. The name of all named vmas are shown in
> /proc/pid/smaps in a new "Name" field that is only present
> for named vmas.
And this is the only purpose, yes?
> static long madvise_behavior(struct vm_area_struct * vma,
> struct vm_area_struct **prev,
> - unsigned long start, unsigned long end, int behavior)
> + unsigned long start, unsigned long end, int behavior,
> + void *arg, size_t arg_len)
> {
> struct mm_struct * mm = vma->vm_mm;
> int error = 0;
> pgoff_t pgoff;
> unsigned long new_flags = vma->vm_flags;
> + struct vma_name *new_name = vma->vm_name;
>
> switch (behavior) {
> case MADV_NORMAL:
> @@ -93,16 +97,28 @@ static long madvise_behavior(struct vm_area_struct * vma,
> if (error)
> goto out;
> break;
> + case MADV_NAME:
> + if (arg) {
> + new_name = vma_name_get_from_str(arg, arg_len);
> + if (!new_name) {
> + error = -ENOMEM;
> + goto out;
> + }
> + } else {
> + new_name = NULL;
> + }
> + break;
> }
>
> - if (new_flags == vma->vm_flags) {
> + if (new_flags == vma->vm_flags && new_name == vma->vm_name) {
> *prev = vma;
> goto out;
> }
>
> pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
> *prev = vma_merge(mm, *prev, start, end, new_flags, vma->anon_vma,
> - vma->vm_file, pgoff, vma_policy(vma));
> + vma->vm_file, pgoff, vma_policy(vma),
> + new_name);
> if (*prev) {
> vma = *prev;
> goto success;
> @@ -127,8 +143,17 @@ success:
> * vm_flags is protected by the mmap_sem held in write mode.
> */
> vma->vm_flags = new_flags;
> + if (vma->vm_name != new_name) {
> + if (vma->vm_name)
> + vma_name_put(vma->vm_name);
> + if (new_name)
> + vma_name_get(new_name);
> + vma->vm_name = new_name;
> + }
So we change vma->vm_name after vma_merge(). But given that is_mergeable_vma()
checks vma->vm_name with this patch, this means that we can have 2 vma's with
the same ->vm_name which should be merged?
IOW. Suppose that we have vma with vm_start = START, end = START + 2 * PAGE_SIZE.
Suppose that an application does
MADV_NAME(START, PAGE_SIZE, "MY_NAME");
MADV_NAME(START + PAGE_SIZE, PAGE_SIZE, "MY_NAME");
The 1st MADV_NAME will split this vma, the 2nd won't merge. Not that I think
this is buggy, just a bit inconsistent imho.
And I guess vma_name_get(new_name) is not needed, you can simply nullify it
after changing ->vm_name to avoid vma_name_put() below.
Oleg.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-07-04 20:28 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-04 1:31 [PATCH] mm: add sys_madvise2 and MADV_NAME to name vmas Colin Cross
2013-07-04 4:54 ` Eric W. Biederman
2013-07-04 6:32 ` Colin Cross
2013-07-05 16:52 ` Oleg Nesterov
2013-07-06 6:33 ` Pekka Enberg
2013-07-06 11:53 ` Eric W. Biederman
2013-07-07 18:35 ` Colin Cross
2013-07-14 1:38 ` Simon Jeons
2013-07-04 8:56 ` Peter Zijlstra
2013-07-05 20:25 ` Colin Cross
2013-07-10 23:20 ` Dave Hansen
2013-07-04 20:22 ` Oleg Nesterov [this message]
2013-07-05 19:40 ` Colin Cross
2013-07-08 18:04 ` [PATCH 0/1] mm: mempolicy: (Was: add sys_madvise2 and MADV_NAME to name vmas) Oleg Nesterov
2013-07-08 18:05 ` [PATCH 1/1] mm: mempolicy: fix mbind_range() && vma_adjust() interaction Oleg Nesterov
2013-07-08 22:29 ` KOSAKI Motohiro
2013-07-09 15:28 ` Oleg Nesterov
2013-07-09 19:43 ` Oleg Nesterov
2013-07-10 2:49 ` KOSAKI Motohiro
2013-07-09 21:56 ` Andrew Morton
2013-07-10 15:45 ` Oleg Nesterov
2013-07-24 9:40 ` [PATCH] mm: add sys_madvise2 and MADV_NAME to name vmas Jan Glauber
2013-07-24 20:05 ` Colin Cross
2013-07-10 23:08 ` Dave Hansen
[not found] ` <CAMbhsRTio2mS=azWTxSdRdaZJRRf5FfMNoQUZmrFjkB7kv9LSQ@mail.gmail.com>
2013-07-10 23:38 ` Dave Hansen
[not found] ` <CAMbhsRTs45QE1ze6mvdiL2QYKD0dHjXoRk7o1h2Y_rYP80ckDg@mail.gmail.com>
2013-07-11 0:19 ` Dave Hansen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130704202232.GA19287@redhat.com \
--to=oleg@redhat.com \
--cc=a.p.zijlstra@chello.nl \
--cc=akpm@linux-foundation.org \
--cc=anton.vorontsov@linaro.org \
--cc=arnd@arndb.de \
--cc=ccross@android.com \
--cc=dave@gnu.org \
--cc=ebiederm@xmission.com \
--cc=gorcunov@openvz.org \
--cc=hannes@cmpxchg.org \
--cc=hch@infradead.org \
--cc=hughd@google.com \
--cc=john.stultz@linaro.org \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=keescook@chromium.org \
--cc=khlebnikov@openvz.org \
--cc=kmpark@infradead.org \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@suse.de \
--cc=mhocko@suse.cz \
--cc=mingo@kernel.org \
--cc=penberg@kernel.org \
--cc=riel@redhat.com \
--cc=rientjes@google.com \
--cc=rob@landley.net \
--cc=rusty@rustcorp.com.au \
--cc=sasha.levin@oracle.com \
--cc=shli@fusionio.com \
--cc=srikar@linux.vnet.ibm.com \
--cc=viro@zeniv.linux.org.uk \
--cc=walken@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).