Re: [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum()

[Salvatore Mesoraca]

2018-03-14 16:42 GMT+01:00 David Sterba :
> We already have a patch for that from a few days ago, but thanks anyway.
>
> https://patchwork.kernel.org/patch/10277901/

Oh.. OK

Best regards,

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

Re: [PATCH] Btrfs: drop a VLA in btrfs_check_super_csum()

[David Sterba]

On Tue, Mar 13, 2018 at 08:50:22PM +0100, Salvatore Mesoraca wrote:
> Avoid a VLA[1] by using a real constant expression instead of a variable.
> The compiler should be able to optimize the original code and avoid using
> an actual VLA. Anyway this change is useful because it will avoid a false
> positive with -Wvla, it might also help the compiler generating better
> code.
> 
> [1] https://lkml.org/lkml/2018/3/7/621
> 
> Signed-off-by: Salvatore Mesoraca 

We already have a patch for that from a few days ago, but thanks anyway.

https://patchwork.kernel.org/patch/10277901/
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH] Btrfs: drop a VLA in btrfs_check_super_csum()

[Salvatore Mesoraca]

Avoid a VLA[1] by using a real constant expression instead of a variable.
The compiler should be able to optimize the original code and avoid using
an actual VLA. Anyway this change is useful because it will avoid a false
positive with -Wvla, it might also help the compiler generating better
code.

[1] https://lkml.org/lkml/2018/3/7/621

Signed-off-by: Salvatore Mesoraca 
---
 fs/btrfs/disk-io.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 21f34ad..88cef92 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -403,8 +403,7 @@ static int btrfs_check_super_csum(struct btrfs_fs_info 
*fs_info,
 
if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
u32 crc = ~(u32)0;
-   const int csum_size = sizeof(crc);
-   char result[csum_size];
+   char result[sizeof(crc)];
 
/*
 * The super_block structure does not span the whole
@@ -415,7 +414,7 @@ static int btrfs_check_super_csum(struct btrfs_fs_info 
*fs_info,
crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
btrfs_csum_final(crc, result);
 
-   if (memcmp(raw_disk_sb, result, csum_size))
+   if (memcmp(raw_disk_sb, result, sizeof(result)))
ret = 1;
}
 
-- 
1.9.1

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