Le 02/05/2021 à 00:50, Khaled ROMDHANI a écrit :

quoted

Fix the warning: variable 'zone' is used
uninitialized whenever '?:' condition is true.

Fix that by preventing the code to reach
the last assertion. If the variable 'mirror'
is invalid, the assertion fails and we return
immediately.

Reported-by: kernel test robot <redacted>
Signed-off-by: Khaled ROMDHANI <redacted>
---
  fs/btrfs/zoned.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 8250ab3f0868..23da9d8dc184 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c

@@ -145,7 +145,7 @@ static inline u32 sb_zone_number(int shift, int mirror)
  	case 2: zone = 1ULL << (BTRFS_SB_LOG_SECOND_SHIFT - shift); break;
  	default:
  		ASSERT((u32)mirror < 3);
-		break;
+		return 0;
  	}
  	ASSERT(zone <= U32_MAX);

base-commit: b5c294aac8a6164ddf38bfbdd1776091b4a1eeba

Hi,

just a few comments.

If I understand correctly, what you try to do is to silence a compiler
warning if no case branch is taken.

First, all your proposals are based on the previous one.
I find it hard to follow because we don't easily see what are the
differences since the beginning.

The "base-commit" at the bottom of your mail, is related to your own local
tree, I guess. It can't be used by any-one.

My understanding it that a patch, should it be v2, v3..., must apply to the
current tree. (In my case, it is the latest linux-next)
This is not the case here and you have to apply each step to see the final
result.

Should this version be fine, a maintainer wouldn't be able to apply it
as-is.

You also try to take into account previous comments to check for incorrect
negative values for minor and catch (the can't happen today) cases, should
BTRFS_SUPER_MIRROR_MAX change and this function remain the same.

So, why hard-coding '3'?
The reason of magic numbers are hard to remember. You should avoid them or
add a comment about it.

My own personal variation would be something like the code below (untested).

Hope this helps.

CJ

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 70b23a0d03b1..75fe5f001d8b 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c

@@ -138,11 +138,14 @@ static inline u32 sb_zone_number(int shift, int

mirror)
 {
 	u64 zone;

-	ASSERT(mirror < BTRFS_SUPER_MIRROR_MAX);
+	ASSERT(mirror >= 0 && mirror < BTRFS_SUPER_MIRROR_MAX);
 	switch (mirror) {
 	case 0: zone = 0; break;
 	case 1: zone = 1ULL << (BTRFS_SB_LOG_FIRST_SHIFT - shift); break;
 	case 2: zone = 1ULL << (BTRFS_SB_LOG_SECOND_SHIFT - shift); break;
+	default:
+		ASSERT(! "mirror < BTRFS_SUPER_MIRROR_MAX but not handled above.");
+		return 0;
 	}

 	ASSERT(zone <= U32_MAX);