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

[Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>]

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);
                congestion_wait(BLK_RW_ASYNC, HZ/50);
        } while (1);
 }
@@ -120,8 +121,9 @@ kmem_zone_alloc(kmem_zone_t *zone, 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);
                congestion_wait(BLK_RW_ASYNC, HZ/50);
        } while (1);
 }
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 8ecffb3..86785b5 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -354,7 +354,8 @@ retry:
                         */
                        if (!(++retries % 100))
                                xfs_err(NULL,
-               "possible memory allocation deadlock in %s (mode:0x%x)",
+                                       "%s(%u) possible memory allocation 
deadlock in %s (mode:0x%x)",
+                                       current->comm, current->pid,
                                        __func__, gfp_mask);
 
                        XFS_STATS_INC(xb_page_retries);
-- 
1.8.3.1