Re: [PATCH 8/8] btrfs: turn on -Wmaybe-uninitialized

[Guenter Roeck <linux@roeck-us.net>]

On Fri, Dec 16, 2022 at 03:15:58PM -0500, Josef Bacik wrote:
> We had a recent bug that would have been caught by a newer compiler with
> -Wmaybe-uninitialized and would have saved us a month of failing tests
> that I didn't have time to investigate.
> 

Thanks to this patch, sparc64:allmodconfig and parisc:allmodconfig now
fail to commpile with the following error when trying to build images
with gcc 11.3.

Building sparc64:allmodconfig ... failed
--------------
Error log:
<stdin>:1517:2: warning: #warning syscall clone3 not implemented [-Wcpp]
fs/btrfs/inode.c: In function 'btrfs_lookup_dentry':
fs/btrfs/inode.c:5730:21: error: 'location.type' may be used uninitialized [-Werror=maybe-uninitialized]
 5730 |         if (location.type == BTRFS_INODE_ITEM_KEY) {
      |             ~~~~~~~~^~~~~
fs/btrfs/inode.c:5719:26: note: 'location' declared here
 5719 |         struct btrfs_key location;

Bisect log attached.

Guenter

---
# bad: [8bf1a529cd664c8e5268381f1e24fe67aa611dd3] Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
# good: [c9c3395d5e3dcc6daee66c6908354d47bf98cb0c] Linux 6.2
git bisect start 'HEAD' 'v6.2'
# good: [e43efb6d713bca3855909a2f9caec280a2b0a503] dt-bindings: riscv: correct starfive visionfive 2 compatibles
git bisect good e43efb6d713bca3855909a2f9caec280a2b0a503
# bad: [1f2d9ffc7a5f916935749ffc6e93fb33bfe94d2f] Merge tag 'sched-core-2023-02-20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect bad 1f2d9ffc7a5f916935749ffc6e93fb33bfe94d2f
# bad: [553637f73c314c742243b8dc5ef072e9dadbe581] Merge tag 'for-6.3/dio-2023-02-16' of git://git.kernel.dk/linux
git bisect bad 553637f73c314c742243b8dc5ef072e9dadbe581
# good: [274978f173276c5720a3cd8d0b6047d2c0d3a684] Merge tag 'fixes_for_v6.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
git bisect good 274978f173276c5720a3cd8d0b6047d2c0d3a684
# bad: [801fcfc5d790f4a9be2897713bd6dd08bed253f1] btrfs: raid56: add a bio_list_put helper
git bisect bad 801fcfc5d790f4a9be2897713bd6dd08bed253f1
# bad: [e2fd83064a9bae368ce1c88a0cb9aee64ad4e124] btrfs: skip backref walking during fiemap if we know the leaf is shared
git bisect bad e2fd83064a9bae368ce1c88a0cb9aee64ad4e124
# bad: [cb0922f264643f03b04352f7a04abb913c609369] btrfs: don't use size classes for zoned file systems
git bisect bad cb0922f264643f03b04352f7a04abb913c609369
# good: [cd30d3bc78d9acbd505d0d6a4cff3b87e40a8187] btrfs: zoned: fix uninitialized variable warning in btrfs_get_dev_zones
git bisect good cd30d3bc78d9acbd505d0d6a4cff3b87e40a8187
# bad: [235e1c7b872f9cf16e8a3e6050a05774b8763c58] btrfs: use a single variable to track return value for log_dir_items()
git bisect bad 235e1c7b872f9cf16e8a3e6050a05774b8763c58
# bad: [d31de3785047a24959eda835b0bafb1f8629f8a9] btrfs: go to matching label when cleaning em in btrfs_submit_direct
git bisect bad d31de3785047a24959eda835b0bafb1f8629f8a9
# bad: [1ec49744ba83f0429c5c706708610f7821a7b6f4] btrfs: turn on -Wmaybe-uninitialized
git bisect bad 1ec49744ba83f0429c5c706708610f7821a7b6f4
# good: [a6ca692ec22bdac5ae700e82ff575a1b5141fa40] btrfs: fix uninitialized variable warning in run_one_async_start
git bisect good a6ca692ec22bdac5ae700e82ff575a1b5141fa40
# first bad commit: [1ec49744ba83f0429c5c706708610f7821a7b6f4] btrfs: turn on -Wmaybe-uninitialized