linux-kernel - Re: [NFS BUG] Resoruces leak caused by commit - NFS: Don't use vm_map_ram() in readdir (55ea499d60aefa3d03a77fc8590c26b5881faa92)

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Date:	Mon, 21 Mar 2011 13:05:19 -0400
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Jacek Luczak <difrost.kernel@...il.com>
Cc:	mkl@...gutronix.de, gregkh@...e.de,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [NFS BUG] Resoruces leak caused by commit - NFS: Don't use
 vm_map_ram() in readdir (55ea499d60aefa3d03a77fc8590c26b5881faa92)

On Mon, 2011-03-21 at 17:53 +0100, Jacek Luczak wrote:
> Hi,
> 
> *BRIEF*: Reading lot of files from nfs mounted on directory lead to a
> resources leak. Affected Kernels: 2.6.37.1-2.6.37.4, did not tested on
> 2.6.38 (assume that issue is also there).
> 
> Steps to reproduce:
>  1) cd /some/nfs/mounted/dir
>  2) find . –type f | wc –l
> On healthy system this will give a number of files below the dir - in
> my test env. this gives 692 files. On broken system after a while when
> whole memory will be consumed this will throw:
> find: memory exhausted
> 
> Reproduced same with rsync to local storage:
> sending incremental file list
> [sender] expand file_list pointer array to 524288 bytes, did move
> [sender] expand file_list pointer array to 1048576 bytes, did move
> [sender] expand file_list pointer array to 2097152 bytes, did move
> [sender] expand file_list pointer array to 4194304 bytes, did move
> [sender] expand file_list pointer array to 8388608 bytes, did move
> [sender] expand file_list pointer array to 16777216 bytes, did move
> [sender] expand file_list pointer array to 33554432 bytes, did move
> [sender] expand file_list pointer array to 67108864 bytes, did move
> [sender] expand file_list pointer array to 134217728 bytes, did move
> [sender] expand file_list pointer array to 268435456 bytes, did move
> [sender] expand file_list pointer array to 402653184 bytes, did move
> [sender] expand file_list pointer array to 536870912 bytes, did move
> [sender] expand file_list pointer array to 671088640 bytes, did move
> [sender] expand file_list pointer array to 805306368 bytes, did move
> [sender] expand file_list pointer array to 939524096 bytes, did move
> [sender] expand file_list pointer array to 1073741824 bytes, did move
> Same results as with find – memory consumption bumps to all available space.
> 
> Bisected this down to commit:
> 55ea499d60aefa3d03a77fc8590c26b5881faa92 is the first bad commit
> commit 55ea499d60aefa3d03a77fc8590c26b5881faa92
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Sat Jan 8 17:45:38 2011 -0500
> 
>     NFS: Don't use vm_map_ram() in readdir
> 
>     commit 6650239a4b01077e80d5a4468562756d77afaa59 upstream.
> 
>     vm_map_ram() is not available on NOMMU platforms, and causes trouble
>     on incoherrent architectures such as ARM when we access the page data
>     through both the direct and the virtual mapping.
> 
>     The alternative is to use the direct mapping to access page data
>     for the case when we are not crossing a page boundary, but to copy
>     the data into a linear scratch buffer when we are accessing data
>     that spans page boundaries.
> 
>     Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
>     Tested-by: Marc Kleine-Budde <mkl@...gutronix.de>
>     Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> 
> :040000 040000 b8416029d026cd8e43d6517bcce32ea86180d31a
> 49dd8041519101ab68075b502ad18127f6ab86d4 M      fs
> :040000 040000 9332a8f43f88b80dd11d76da0e35bfdfe345798f
> 71b519dd4ce6fe70a9ecaa1e068bc56ea7c0cd4e M      include
> :040000 040000 d4f45b70708f5d238eacececb9459c7a88d8ec77
> f70bedd7247a37e14972448f5f1803edc1440fc4 M      net
> 
> Reverting this commit fixes this issue.

Does the attached patch help? It fixes an old readdir decoding bug that
the above commit happened to expose.

Trond
-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com


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