Re: [PATCH v2] ext2: Make sbi an proper alias for EXT2_SB(sb) in ext2_fill_super()

[sashiko-bot@kernel.org]

> A recent LLVM change to fix parsing and validating __guarded_by on
> structure members [1] reveals a couple of warnings in ext2_fill_super()
> from the annotations added by commit 023051c2d0f1 ("ext2: mark
> s_mount_state as guarded by s_lock") and commit c23746524faf ("ext2:
> annotate s_rsv_window_root as requiring s_rsv_window_lock"):
> 
>   fs/ext2/super.c:1040:7: error: writing variable 's_mount_state' requires holding spinlock '_res->s_lock' exclusively [-Werror,-Wthread-safety-precise]
>    1040 |         sbi->s_mount_state = le16_to_cpu(es->s_state);
>         |              ^
>   fs/ext2/super.c:1040:7: note: found near match 'EXT2_SB(sb).s_lock'
>   fs/ext2/super.c:1138:8: error: writing variable 's_rsv_window_root' requires holding spinlock '_res->s_rsv_window_lock' exclusively [-Werror,-Wthread-safety-precise]
>    1138 |                 sbi->s_rsv_window_root = RB_ROOT;
>         |                      ^
>   fs/ext2/super.c:1138:8: note: found near match 'EXT2_SB(sb).s_rsv_window_lock'
> 
> Context analysis does very minimal alias detection [2], so it is not
> able to figure out that sbi == sb->s_fs_info == EXT2_SB(sb). The only
> reason there were no warnings before the above LLVM change is because
> the annotation was not parsed and verified correctly.
> 
> Rework the allocation and assignment of sbi to have a direct assignment
> of EXT2_SB(sb) to sbi so that the analysis knows that sbi and
> EXT2_SB(sb) refer to the same object, clearing up the warnings.
> 
> Fixes: 9708538ba204 ("ext2: enable context analysis support for ext2 filesystem")
> Link: https://github.com/llvm/llvm-project/commit/217e229a1f32785fccdd3b3f51429f0d309dea45 [1]
> Link: https://clang.llvm.org/docs/ThreadSafetyAnalysis.html#no-alias-analysis [2]
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261023-ext2-fix-context-analysis-clang-24-v2-1-a33961453899@kernel.org?part=1