On 2018/9/25 下午11:34, David Sterba wrote:
> On Tue, Sep 25, 2018 at 08:06:26AM +0800, Qu Wenruo wrote:
>> Although BTRFS_NAME_LEN and XATTR_NAME_MAX is the same value (255),
>> max(BTRFS_NAME_LEN, XATTR_NAME_MAX) should be optimized as const at
>> runtime.
>>
>> However S390x' arch dependent option "-mwarn-dynamicstack" could still
>> report it as dyanamic stack allocation.
>>
>> Just use BTRFS_NAME_LEN directly to avoid such false alert.
>
> Same reasoning as for the NAME_MAX, these are different things.
>
>> Signed-off-by: Qu Wenruo <w...@suse.com>
>> ---
>> fs/btrfs/tree-checker.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
>> index db835635372f..4c045609909b 100644
>> --- a/fs/btrfs/tree-checker.c
>> +++ b/fs/btrfs/tree-checker.c
>> @@ -336,7 +336,7 @@ static int check_dir_item(struct btrfs_fs_info *fs_info,
>> */
>> if (key->type == BTRFS_DIR_ITEM_KEY ||
>> key->type == BTRFS_XATTR_ITEM_KEY) {
>> - char namebuf[max(BTRFS_NAME_LEN, XATTR_NAME_MAX)];
>> + char namebuf[BTRFS_NAME_LEN];
>
> The updated implementation of max() can now handle the expression
> without a warning, with sufficiently new compiler so I don't think we
> need to fix that.Yes, it's mostly a workaround to make S390 happy. And if it can be fixed by kernel config/compiler, it doesn't make much sense to fix it here. So please discard these 2 patches. Thanks, Qu > > Alternatively, you could use BTRFS_NAME_LEN and add a > BUILD_BUG_ON(BTRFS_NAME_LEN < XATTR_NAME_MAX) with a comment why. > >> >> read_extent_buffer(leaf, namebuf, >> (unsigned long)(di + 1), name_len); >> -- >> 2.19.0
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