* [PATCH] btrfs: Use sizeof directly instead of a constant variable
@ 2018-03-12 16:52 Nikolay Borisov
2018-03-12 16:58 ` David Sterba
2018-03-13 8:26 ` [PATCH v2] " Nikolay Borisov
0 siblings, 2 replies; 4+ messages in thread
From: Nikolay Borisov @ 2018-03-12 16:52 UTC (permalink / raw)
To: linux-btrfs; +Cc: Nikolay Borisov
The kernel would like to have all stack VLA usage removed[1].
Unfortunately using an integer constant variable as the size of an
array is still considered a VLA. Instead let's use directly sizeof(var)
which removes the VLA usage. Use the occasion to remove csum_size
altogether and use sizeof() also for the size passed to memcmp
[1]: https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
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 3809d6d66f6a..6247162e334a 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(crc)))
ret = 1;
}
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] btrfs: Use sizeof directly instead of a constant variable
2018-03-12 16:52 [PATCH] btrfs: Use sizeof directly instead of a constant variable Nikolay Borisov
@ 2018-03-12 16:58 ` David Sterba
2018-03-13 8:26 ` [PATCH v2] " Nikolay Borisov
1 sibling, 0 replies; 4+ messages in thread
From: David Sterba @ 2018-03-12 16:58 UTC (permalink / raw)
To: Nikolay Borisov; +Cc: linux-btrfs
On Mon, Mar 12, 2018 at 06:52:28PM +0200, Nikolay Borisov wrote:
> The kernel would like to have all stack VLA usage removed[1].
> Unfortunately using an integer constant variable as the size of an
> array is still considered a VLA. Instead let's use directly sizeof(var)
> which removes the VLA usage. Use the occasion to remove csum_size
> altogether and use sizeof() also for the size passed to memcmp
The point of csum_size here is to define once, use everywhere, so we
don't have to opencode sizeof. To avoid the 'not really a VLA', we can
rewrite that.
>
> [1]: https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
> 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 3809d6d66f6a..6247162e334a 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(crc)))
sizeof(result) would be better here as it's clear what we're going to
memcpy, while 'crc' is define somewhere above.
> ret = 1;
> }
>
> --
> 2.7.4
>
> --
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> the body of a message to majordomo@vger.kernel.org
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^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] btrfs: Use sizeof directly instead of a constant variable
2018-03-12 16:52 [PATCH] btrfs: Use sizeof directly instead of a constant variable Nikolay Borisov
2018-03-12 16:58 ` David Sterba
@ 2018-03-13 8:26 ` Nikolay Borisov
2018-03-14 18:20 ` David Sterba
1 sibling, 1 reply; 4+ messages in thread
From: Nikolay Borisov @ 2018-03-13 8:26 UTC (permalink / raw)
To: linux-btrfs; +Cc: Nikolay Borisov
The kernel would like to have all stack VLA usage removed[1].
Unfortunately using an integer constant variable as the size of an
array is still considered a VLA. Instead let's use directly sizeof(var)
which removes the VLA usage. Use the occasion to remove csum_size
altogether and use sizeof() also for the size passed to memcmp
[1]: https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
V2:
* Use sizeof(result) in memcmp to make it more clear what we are comparing.
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 3809d6d66f6a..04834cb65272 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;
}
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] btrfs: Use sizeof directly instead of a constant variable
2018-03-13 8:26 ` [PATCH v2] " Nikolay Borisov
@ 2018-03-14 18:20 ` David Sterba
0 siblings, 0 replies; 4+ messages in thread
From: David Sterba @ 2018-03-14 18:20 UTC (permalink / raw)
To: Nikolay Borisov; +Cc: linux-btrfs
On Tue, Mar 13, 2018 at 10:26:06AM +0200, Nikolay Borisov wrote:
> The kernel would like to have all stack VLA usage removed[1].
> Unfortunately using an integer constant variable as the size of an
> array is still considered a VLA. Instead let's use directly sizeof(var)
> which removes the VLA usage. Use the occasion to remove csum_size
> altogether and use sizeof() also for the size passed to memcmp
>
> [1]: https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
>
> V2:
> * Use sizeof(result) in memcmp to make it more clear what we are comparing.
Reviewed-by: David Sterba <dsterba@suse.com>
Added to next, thanks.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2018-03-12 16:52 [PATCH] btrfs: Use sizeof directly instead of a constant variable Nikolay Borisov
2018-03-12 16:58 ` David Sterba
2018-03-13 8:26 ` [PATCH v2] " Nikolay Borisov
2018-03-14 18:20 ` David Sterba
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