From: Arnd Bergmann <[email protected]>
gcc complains that the ctl->max_chunk_size member might be used
uninitialized when none of the three conditions for initializing it in
init_alloc_chunk_ctl_policy_zoned() are true:
In function ‘init_alloc_chunk_ctl_policy_zoned’,
inlined from ‘init_alloc_chunk_ctl’ at fs/btrfs/volumes.c:5023:3,
inlined from ‘btrfs_alloc_chunk’ at fs/btrfs/volumes.c:5340:2:
include/linux/compiler-gcc.h:48:45: error: ‘ctl.max_chunk_size’ may be used uninitialized [-Werror=maybe-uninitialized]
4998 | ctl->max_chunk_size = min(limit, ctl->max_chunk_size);
| ^~~
fs/btrfs/volumes.c: In function ‘btrfs_alloc_chunk’:
fs/btrfs/volumes.c:5316:32: note: ‘ctl’ declared here
5316 | struct alloc_chunk_ctl ctl;
| ^~~
If we ever get into this condition, something is seriously
wrong, so the same logic as in init_alloc_chunk_ctl_policy_regular()
and a few other places should be applied. This avoids both further
data corruption, and the compile-time warning.
Fixes: 1cd6121f2a38 ("btrfs: zoned: implement zoned chunk allocator")
Link: https://lore.kernel.org/lkml/[email protected]/
Suggested-by: David Sterba <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
---
Note that the -Wmaybe-unintialized warning is globally disabled
by default. For some reason I got this warning anyway when building
this specific file with gcc-11.
---
fs/btrfs/volumes.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index bc3b33efddc5..d2994305ed77 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4989,6 +4989,8 @@ static void init_alloc_chunk_ctl_policy_zoned(
ctl->max_chunk_size = 2 * ctl->max_stripe_size;
ctl->devs_max = min_t(int, ctl->devs_max,
BTRFS_MAX_DEVS_SYS_CHUNK);
+ } else {
+ BUG();
}
/* We don't want a chunk larger than 10% of writable space */
--
2.29.2
On Tue, Mar 23, 2021 at 03:31:19PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> gcc complains that the ctl->max_chunk_size member might be used
> uninitialized when none of the three conditions for initializing it in
> init_alloc_chunk_ctl_policy_zoned() are true:
>
> In function ‘init_alloc_chunk_ctl_policy_zoned’,
> inlined from ‘init_alloc_chunk_ctl’ at fs/btrfs/volumes.c:5023:3,
> inlined from ‘btrfs_alloc_chunk’ at fs/btrfs/volumes.c:5340:2:
> include/linux/compiler-gcc.h:48:45: error: ‘ctl.max_chunk_size’ may be used uninitialized [-Werror=maybe-uninitialized]
> 4998 | ctl->max_chunk_size = min(limit, ctl->max_chunk_size);
> | ^~~
> fs/btrfs/volumes.c: In function ‘btrfs_alloc_chunk’:
> fs/btrfs/volumes.c:5316:32: note: ‘ctl’ declared here
> 5316 | struct alloc_chunk_ctl ctl;
> | ^~~
>
> If we ever get into this condition, something is seriously
> wrong, so the same logic as in init_alloc_chunk_ctl_policy_regular()
> and a few other places should be applied. This avoids both further
> data corruption, and the compile-time warning.
>
> Fixes: 1cd6121f2a38 ("btrfs: zoned: implement zoned chunk allocator")
> Link: https://lore.kernel.org/lkml/[email protected]/
> Suggested-by: David Sterba <[email protected]>
> Signed-off-by: Arnd Bergmann <[email protected]>
Added to misc-next, thanks.