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btrfs: make sure to initialize start and len in find_free_dev_extent

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Jens reported a compiler error when using CONFIG_CC_OPTIMIZE_FOR_SIZE=y
that looks like this

  In function ‘gather_device_info’,
      inlined from ‘btrfs_create_chunk’ at fs/btrfs/volumes.c:5507:8:
  fs/btrfs/volumes.c:5245:48: warning: ‘dev_offset’ may be used uninitialized [-Wmaybe-uninitialized]
   5245 |                 devices_info[ndevs].dev_offset = dev_offset;
	|                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
  fs/btrfs/volumes.c: In function ‘btrfs_create_chunk’:
  fs/btrfs/volumes.c:5196:13: note: ‘dev_offset’ was declared here
   5196 |         u64 dev_offset;

This occurs because find_free_dev_extent is responsible for setting
dev_offset, however if we get an -ENOMEM at the top of the function
we'll return without setting the value.

This isn't actually a problem because we will see the -ENOMEM in
gather_device_info() and return and not use the uninitialized value,
however we also just don't want the compiler warning so rework the code
slightly in find_free_dev_extent() to make sure it's always setting
*start and *len to avoid the compiler warning.

Reported-by: Jens Axboe <axboe@kernel.dk>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2023-09-05 12:15:23 -04:00 • committed by David Sterba
parent 74ee79142c
commit 20218dfbaa
1 changed files with 6 additions and 7 deletions
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13
fs/btrfs/volumes.c
View file

@ -1594,7 +1594,7 @@ static int find_free_dev_extent(struct btrfs_device *device, u64 num_bytes,
u64 search_start;
u64 hole_size;
u64 max_hole_start;
u64 max_hole_size;
u64 max_hole_size = 0;
u64 extent_end;
u64 search_end = device->total_bytes;
int ret;
@ -1602,17 +1602,16 @@ static int find_free_dev_extent(struct btrfs_device *device, u64 num_bytes,
struct extent_buffer *l;
search_start = dev_extent_search_start(device);
max_hole_start = search_start;
WARN_ON(device->zone_info &&
!IS_ALIGNED(num_bytes, device->zone_info->zone_size));
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
max_hole_start = search_start;
max_hole_size = 0;
if (!path) {
ret = -ENOMEM;
goto out;
}
again:
if (search_start >= search_end ||
test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {