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Re: XFS memory allocation deadlock in 2.6.38

To: "'Christoph Hellwig'" <hch@xxxxxxxxxxxxx>
Subject: Re: XFS memory allocation deadlock in 2.6.38
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 30 Mar 2011 09:42:30 +1100
Cc: Sean Noonan <Sean.Noonan@xxxxxxxxxxxx>, Trammell Hudson <Trammell.Hudson@xxxxxxxxxxxx>, Christos Zoulas <Christos.Zoulas@xxxxxxxxxxxx>, Martin Bligh <Martin.Bligh@xxxxxxxxxxxx>, "'linux-kernel@xxxxxxxxxxxxxxx'" <linux-kernel@xxxxxxxxxxxxxxx>, Stephen Degler <Stephen.Degler@xxxxxxxxxxxx>, "'linux-mm@xxxxxxxxx'" <linux-mm@xxxxxxxxx>, "'linux-xfs@xxxxxxxxxxx'" <linux-xfs@xxxxxxxxxxx>, "'Michel Lespinasse'" <walken@xxxxxxxxxx>
In-reply-to: <20110329200256.GA6019@xxxxxxxxxxxxx>
References: <081DDE43F61F3D43929A181B477DCA95639B5327@xxxxxxxxxxxxxxxxxxxx> <20110324174311.GA31576@xxxxxxxxxxxxx> <AANLkTikwwRm6FHFtEdUg54NvmKdswQw-NPH5dtq1mXBK@xxxxxxxxxxxxxx> <081DDE43F61F3D43929A181B477DCA95639B5349@xxxxxxxxxxxxxxxxxxxx> <BANLkTin0jJevStg5P2hqsLbqMzo3o30sYg@xxxxxxxxxxxxxx> <081DDE43F61F3D43929A181B477DCA95639B534E@xxxxxxxxxxxxxxxxxxxx> <081DDE43F61F3D43929A181B477DCA95639B5359@xxxxxxxxxxxxxxxxxxxx> <20110329192434.GA10536@xxxxxxxxxxxxx> <081DDE43F61F3D43929A181B477DCA95639B535C@xxxxxxxxxxxxxxxxxxxx> <20110329200256.GA6019@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
On Tue, Mar 29, 2011 at 04:02:56PM -0400, 'Christoph Hellwig' wrote:
> On Tue, Mar 29, 2011 at 03:46:21PM -0400, Sean Noonan wrote:
> > > Can you check if the brute force patch below helps?
> > 
> > No such luck.
> 
> Actually thinking about it - we never do the vmalloc under any fs lock,
> so this can't be the reason.  But nothing else in the patch spring to
> mind either, so to narrow this down does reverting the patch on
> 2.6.38 also fix it?  The revert isn't quite trivial due to changes
> since then, so here's the patch I came up with:
> 
> 
> Index: xfs/fs/xfs/linux-2.6/kmem.c
> ===================================================================
> --- xfs.orig/fs/xfs/linux-2.6/kmem.c  2011-03-29 21:55:12.871726512 +0200
> +++ xfs/fs/xfs/linux-2.6/kmem.c       2011-03-29 21:55:31.648723706 +0200
> @@ -16,6 +16,7 @@
>   * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
>   */
>  #include <linux/mm.h>
> +#include <linux/vmalloc.h>
>  #include <linux/highmem.h>
>  #include <linux/slab.h>
>  #include <linux/swap.h>
> @@ -25,25 +26,8 @@
>  #include "kmem.h"
>  #include "xfs_message.h"
>  
> -/*
> - * Greedy allocation.  May fail and may return vmalloced memory.
> - *
> - * Must be freed using kmem_free_large.
> - */
> -void *
> -kmem_zalloc_greedy(size_t *size, size_t minsize, size_t maxsize)
> -{
> -     void            *ptr;
> -     size_t          kmsize = maxsize;
> -
> -     while (!(ptr = kmem_zalloc_large(kmsize))) {
> -             if ((kmsize >>= 1) <= minsize)
> -                     kmsize = minsize;
> -     }
> -     if (ptr)
> -             *size = kmsize;
> -     return ptr;
> -}
> +#define MAX_VMALLOCS 6
> +#define MAX_SLAB_SIZE        0x20000

Why those values for the magic numbers?

....

> Index: xfs/fs/xfs/quota/xfs_qm.c
> ===================================================================
> --- xfs.orig/fs/xfs/quota/xfs_qm.c    2011-03-29 21:55:12.859726589 +0200
> +++ xfs/fs/xfs/quota/xfs_qm.c 2011-03-29 21:55:41.387278609 +0200
> @@ -110,11 +110,12 @@ xfs_Gqm_init(void)
>        */
>       udqhash = kmem_zalloc_greedy(&hsize,
>                                    XFS_QM_HASHSIZE_LOW * sizeof(xfs_dqhash_t),
> -                                  XFS_QM_HASHSIZE_HIGH * 
> sizeof(xfs_dqhash_t));
> +                                  XFS_QM_HASHSIZE_HIGH * 
> sizeof(xfs_dqhash_t),
> +                                  KM_SLEEP | KM_MAYFAIL | KM_LARGE);
>       if (!udqhash)
>               goto out;
>  
> -     gdqhash = kmem_zalloc_large(hsize);
> +     gdqhash = kmem_zalloc(hsize, KM_SLEEP | KM_LARGE);

Needs a KM_MAYFAIL as well?

>       if (!gdqhash)
>               goto out_free_udqhash;
>  
....
> Index: xfs/fs/xfs/xfs_itable.c
> ===================================================================
> --- xfs.orig/fs/xfs/xfs_itable.c      2011-03-29 21:55:12.851725366 +0200
> +++ xfs/fs/xfs/xfs_itable.c   2011-03-29 21:55:31.660724287 +0200
> @@ -259,10 +259,8 @@ xfs_bulkstat(
>               (XFS_INODE_CLUSTER_SIZE(mp) >> mp->m_sb.sb_inodelog);
>       nimask = ~(nicluster - 1);
>       nbcluster = nicluster >> mp->m_sb.sb_inopblog;
> -     irbuf = kmem_zalloc_greedy(&irbsize, PAGE_SIZE, PAGE_SIZE * 4);
> -     if (!irbuf)
> -             return ENOMEM;
> -
> +     irbuf = kmem_zalloc_greedy(&irbsize, PAGE_SIZE, PAGE_SIZE * 4,
> +                                KM_SLEEP | KM_MAYFAIL | KM_LARGE);
>       nirbuf = irbsize / sizeof(*irbuf);

Need to keep the if (!irbuf) check as KM_MAYFAIL is passed.

Cheers,

Dave
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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