[PATCH] btrfs: zoned: fix uninitialized max_chunk_size

From: Arnd Bergmann
Date: Tue Mar 23 2021 - 08:47:08 EST

From: Arnd Bergmann <arnd@xxxxxxxx>

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;
| ^~~

Initialize it to UINT_MAX and rely on the min() expression to limit

Fixes: 1cd6121f2a38 ("btrfs: zoned: implement zoned chunk allocator")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
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 | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index bc3b33efddc5..b42b423b6a10 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4980,6 +4980,7 @@ static void init_alloc_chunk_ctl_policy_zoned(
u64 type = ctl->type;

ctl->max_stripe_size = zone_size;
+ ctl->max_chunk_size = UINT_MAX;
ctl->max_chunk_size = round_down(BTRFS_MAX_DATA_CHUNK_SIZE,