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Re: [PATCH 10/12] fs/xfs: Correct redundant test

To: Julia Lawall <julia@xxxxxxx>
Subject: Re: [PATCH 10/12] fs/xfs: Correct redundant test
From: Felix Blyakher <felixb@xxxxxxx>
Date: Mon, 27 Jul 2009 11:37:13 -0500
Cc: xfs-masters@xxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, kernel-janitors@xxxxxxxxxxxxxxx
In-reply-to: <Pine.LNX.4.64.0907271815060.2682@xxxxxxxxxxx>
References: <Pine.LNX.4.64.0907271815060.2682@xxxxxxxxxxx>

On Jul 27, 2009, at 11:15 AM, Julia Lawall wrote:

From: Julia Lawall <julia@xxxxxxx>

bp was tested for NULL a few lines before, followed by a return, and there
is no intervening modification of its value.

A simplified version of the semantic match that finds this problem is as
follows: (http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@r exists@
local idexpression x;
expression E;
position p1,p2;
@@

if (x == NULL || ...) { ... when forall
  return ...; }
... when != \(x=E\|x--\|x++\|--x\|++x\|x-=E\|x+=E\|x|=E\|x&=E\|&x\)
(
*x == NULL
|
*x != NULL
)
// </smpl>

Signed-off-by: Julia Lawall <julia@xxxxxxx>

Looks good. Thanks. I'll check it in.

Reviewed-by: Felix Blyakher <felixb@xxxxxxx>



---
fs/xfs/xfs_trans_buf.c              |    4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
index 8ee2f8c..218829e 100644
--- a/fs/xfs/xfs_trans_buf.c
+++ b/fs/xfs/xfs_trans_buf.c
@@ -307,7 +307,7 @@ xfs_trans_read_buf(
                        return (flags & XFS_BUF_TRYLOCK) ?
                                        EAGAIN : XFS_ERROR(ENOMEM);

-               if ((bp != NULL) && (XFS_BUF_GETERROR(bp) != 0)) {
+               if (XFS_BUF_GETERROR(bp) != 0) {
                        xfs_ioerror_alert("xfs_trans_read_buf", mp,
                                          bp, blkno);
                        error = XFS_BUF_GETERROR(bp);
@@ -315,7 +315,7 @@ xfs_trans_read_buf(
                        return error;
                }
#ifdef DEBUG
-               if (xfs_do_error && (bp != NULL)) {
+               if (xfs_do_error) {
                        if (xfs_error_target == target) {
                                if (((xfs_req_num++) % xfs_error_mod) == 0) {
                                        xfs_buf_relse(bp);

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