ext4: remove unreachable code in ext4_can_extents_be_merged()

Submitted by Eric Sandeen on Oct. 31, 2013, 9 p.m.

Details

Message ID 5272C4E3.5040206@redhat.com
State Accepted, archived
Headers show

Commit Message

Eric Sandeen Oct. 31, 2013, 9 p.m.
commit
ec22ba8e ext4: disable merging of uninitialized extents

ensured that if either extent under consideration is uninit,
we decline to merge, and immediately return.

But right after that test, we test again for an uninit
extent; we can never hit this.  So just remove the impossible
test and associated variable.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

Disclosure: compile-tested only.


--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Comments

Zheng Liu Nov. 1, 2013, 3:05 a.m.
On Thu, Oct 31, 2013 at 04:00:19PM -0500, Eric Sandeen wrote:
> commit
> ec22ba8e ext4: disable merging of uninitialized extents
> 
> ensured that if either extent under consideration is uninit,
> we decline to merge, and immediately return.
> 
> But right after that test, we test again for an uninit
> extent; we can never hit this.  So just remove the impossible
> test and associated variable.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Looks good to me.
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>

Thanks,
                                                - Zheng

> ---
> 
> Disclosure: compile-tested only.
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 54d52af..de6d467 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1666,7 +1666,7 @@ int
>  ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
>  				struct ext4_extent *ex2)
>  {
> -	unsigned short ext1_ee_len, ext2_ee_len, max_len;
> +	unsigned short ext1_ee_len, ext2_ee_len;
>  
>  	/*
>  	 * Make sure that both extents are initialized. We don't merge
> @@ -1677,11 +1677,6 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
>  	if (ext4_ext_is_uninitialized(ex1) || ext4_ext_is_uninitialized(ex2))
>  		return 0;
>  
> -	if (ext4_ext_is_uninitialized(ex1))
> -		max_len = EXT_UNINIT_MAX_LEN;
> -	else
> -		max_len = EXT_INIT_MAX_LEN;
> -
>  	ext1_ee_len = ext4_ext_get_actual_len(ex1);
>  	ext2_ee_len = ext4_ext_get_actual_len(ex2);
>  
> @@ -1694,7 +1689,7 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
>  	 * as an RO_COMPAT feature, refuse to merge to extents if
>  	 * this can result in the top bit of ee_len being set.
>  	 */
> -	if (ext1_ee_len + ext2_ee_len > max_len)
> +	if (ext1_ee_len + ext2_ee_len > EXT_INIT_MAX_LEN)
>  		return 0;
>  #ifdef AGGRESSIVE_TEST
>  	if (ext1_ee_len >= 4)
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Theodore Ts'o Nov. 8, 2013, 3:26 a.m.
On Thu, Oct 31, 2013 at 04:00:19PM -0500, Eric Sandeen wrote:
> commit
> ec22ba8e ext4: disable merging of uninitialized extents
> 
> ensured that if either extent under consideration is uninit,
> we decline to merge, and immediately return.
> 
> But right after that test, we test again for an uninit
> extent; we can never hit this.  So just remove the impossible
> test and associated variable.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Thanks, applied

					- Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch hide | download patch | download mbox

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 54d52af..de6d467 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -1666,7 +1666,7 @@  int
 ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
 				struct ext4_extent *ex2)
 {
-	unsigned short ext1_ee_len, ext2_ee_len, max_len;
+	unsigned short ext1_ee_len, ext2_ee_len;
 
 	/*
 	 * Make sure that both extents are initialized. We don't merge
@@ -1677,11 +1677,6 @@  ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
 	if (ext4_ext_is_uninitialized(ex1) || ext4_ext_is_uninitialized(ex2))
 		return 0;
 
-	if (ext4_ext_is_uninitialized(ex1))
-		max_len = EXT_UNINIT_MAX_LEN;
-	else
-		max_len = EXT_INIT_MAX_LEN;
-
 	ext1_ee_len = ext4_ext_get_actual_len(ex1);
 	ext2_ee_len = ext4_ext_get_actual_len(ex2);
 
@@ -1694,7 +1689,7 @@  ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
 	 * as an RO_COMPAT feature, refuse to merge to extents if
 	 * this can result in the top bit of ee_len being set.
 	 */
-	if (ext1_ee_len + ext2_ee_len > max_len)
+	if (ext1_ee_len + ext2_ee_len > EXT_INIT_MAX_LEN)
 		return 0;
 #ifdef AGGRESSIVE_TEST
 	if (ext1_ee_len >= 4)