xfs: only trace buffer items if they exist

The commit 2d3d0c5 ("xfs: lobotomise xfs_trans_read_buf_map()") left
a landmine in the tracing code: trace_xfs_trans_buf_read() is now
call on all buffers that are read through this interface rather than
just buffers in transactions. For buffers outside transaction
context, bp->b_fspriv is null, and so the buf log item tracing
functions cannot be called. This causes a NULL pointer dereference
in the trace_xfs_trans_buf_read() function when tracing is turned
on.

cc: <stable@vger.kernel.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Dave Chinner 2015-02-10 09:23:40 +11:00 committed by Dave Chinner
parent 01f9882eac
commit e9892d3cc8

View file

@ -327,9 +327,10 @@ xfs_trans_read_buf_map(
return -EIO;
}
if (tp)
if (tp) {
_xfs_trans_bjoin(tp, bp, 1);
trace_xfs_trans_read_buf(bp->b_fspriv);
trace_xfs_trans_read_buf(bp->b_fspriv);
}
*bpp = bp;
return 0;