Re: [PATCH v2] xfs: Print comm name and pid when open-coded __GFP_NOFAIL allocation stucks

[Dave Chinner <david@xxxxxxxxxxxxx>]

On Mon, Sep 21, 2015 at 10:23:57AM +0900, Tetsuo Handa wrote:
> This patch adds comm name and pid to warning messages printed by
> kmem_alloc(), kmem_zone_alloc() and xfs_buf_allocate_memory().
> This will help telling which memory allocations (e.g. kernel worker
> threads, OOM victim tasks, neither) are stalling because these functions
> are passing __GFP_NOWARN which suppresses not only backtrace but comm name
> and pid.
> 
>   [  135.568662] Out of memory: Kill process 9593 (a.out) score 998 or 
> sacrifice child
>   [  135.570195] Killed process 9593 (a.out) total-vm:4700kB, anon-rss:488kB, 
> file-rss:0kB
>   [  137.473691] XFS: kworker/u16:29(383) possible memory allocation deadlock 
> in xfs_buf_allocate_memory (mode:0x1250)
>   [  137.497662] XFS: a.out(8944) possible memory allocation deadlock in 
> xfs_buf_allocate_memory (mode:0x1250)
>   [  137.598219] XFS: a.out(9658) possible memory allocation deadlock in 
> xfs_buf_allocate_memory (mode:0x1250)
>   [  139.494529] XFS: kworker/u16:29(383) possible memory allocation deadlock 
> in xfs_buf_allocate_memory (mode:0x1250)
>   [  139.517196] XFS: a.out(8944) possible memory allocation deadlock in 
> xfs_buf_allocate_memory (mode:0x1250)
>   [  139.616396] XFS: a.out(9658) possible memory allocation deadlock in 
> xfs_buf_allocate_memory (mode:0x1250)
>   [  141.512753] XFS: kworker/u16:29(383) possible memory allocation deadlock 
> in xfs_buf_allocate_memory (mode:0x1250)
>   [  141.531421] XFS: a.out(8944) possible memory allocation deadlock in 
> xfs_buf_allocate_memory (mode:0x1250)
>   [  141.633574] XFS: a.out(9658) possible memory allocation deadlock in 
> xfs_buf_allocate_memory (mode:0x1250)
> 
> (Strictly speaking, we want task_lock()/task_unlock() when reading comm name.)
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> ---
>  fs/xfs/kmem.c    | 10 ++++++----
>  fs/xfs/xfs_buf.c |  3 ++-
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/xfs/kmem.c b/fs/xfs/kmem.c
> index a7a3a63..735095a 100644
> --- a/fs/xfs/kmem.c
> +++ b/fs/xfs/kmem.c
> @@ -55,8 +55,9 @@ kmem_alloc(size_t size, xfs_km_flags_t flags)
>                       return ptr;
>               if (!(++retries % 100))
>                       xfs_err(NULL,
> -             "possible memory allocation deadlock in %s (mode:0x%x)",
> -                                     __func__, lflags);
> +                             "%s(%u) possible memory allocation deadlock in 
> %s (mode:0x%x)",
> +                             current->comm, current->pid,
> +                             __func__, lflags);

<=80 columns, please.

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx