2009-07-27 16:18:52

by Julia Lawall

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

From: Julia Lawall <[email protected]>

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 <[email protected]>

---
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);

2009-07-27 16:37:14

by Felix Blyakher

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

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

> From: Julia Lawall <[email protected]>
>
> 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 <[email protected]>

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

Reviewed-by: Felix Blyakher <[email protected]>

>
>
> ---
> 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);