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ext4: fix oops in trace_ext4_mb_release_group_pa

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Our QA reported an oops in the ext4_mb_release_group_pa tracing,
and Josef Bacik pointed out that it was because we may have a
non-null but uninitialized ac_inode in the allocation context.

I can reproduce it when running xfstests with ext4 tracepoints on, 
on a CONFIG_SLAB_DEBUG kernel.

We call trace_ext4_mb_release_group_pa from 2 places, 
ext4_mb_discard_group_preallocations and 
ext4_mb_discard_lg_preallocations

In both cases we allocate an ac as a container just for tracing (!)
and never fill in the ac_inode.  There's no reason to be assigning,
testing, or printing it as far as I can see, so just remove it from
the tracepoint.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Josef Bacik <josef@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Eric Sandeen 2010-10-27 21:30:07 -04:00 committed by Theodore Ts'o
parent 0c9169ccad
commit 4d5476164a
1 changed files with 0 additions and 3 deletions
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3
include/trace/events/ext4.h
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@ -432,7 +432,6 @@ TRACE_EVENT(ext4_mb_release_group_pa,
TP_STRUCT__entry(
__field( dev_t, dev )
__field( ino_t, ino )
__field( __u64, pa_pstart )
__field( __u32, pa_len )
@ -440,8 +439,6 @@ TRACE_EVENT(ext4_mb_release_group_pa,
TP_fast_assign(
__entry->dev = sb->s_dev;
__entry->ino = (ac && ac->ac_inode) ?
ac->ac_inode->i_ino : 0;
__entry->pa_pstart = pa->pa_pstart;
__entry->pa_len = pa->pa_len;
),