xfs: only trace buffer items if they exist
authorDave Chinner <dchinner@redhat.com>
Mon, 9 Feb 2015 22:23:40 +0000 (09:23 +1100)
committerDave Chinner <david@fromorbit.com>
Mon, 9 Feb 2015 22:23:40 +0000 (09:23 +1100)
commite9892d3cc853afdda2cc69e2576d9ddb5fafad71
tree83f14e59af392ab6880990b04bdbf1892e7acc74
parent01f9882eac84b85421a469cb65ee9bb555a5985f
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>
fs/xfs/xfs_trans_buf.c