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| author | Kent Overstreet <kent.overstreet@linux.dev> | 2024-07-30 20:35:59 -0400 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2024-08-07 08:31:10 -0400 |
| commit | 90b211fa2da3f36939e84b6426988832a62caf4b (patch) | |
| tree | 037c261011f12a3d34af04675d7693582773edda /fs | |
| parent | 7442b5cdf259e2fb112560904b7002ce48d15578 (diff) | |
bcachefs: Add a comment for bucket helper types
We've had bugs in the past with incorrect integer conversions in disk
accounting code, which is why bucket helpers now always return s64s; add
a comment explaining this.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/bcachefs/alloc_background.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/fs/bcachefs/alloc_background.h b/fs/bcachefs/alloc_background.h index f13e619b4b21..96a0444ea78f 100644 --- a/fs/bcachefs/alloc_background.h +++ b/fs/bcachefs/alloc_background.h @@ -82,6 +82,14 @@ static inline bool bucket_data_type_mismatch(enum bch_data_type bucket, bucket_data_type(bucket) != bucket_data_type(ptr); } +/* + * It is my general preference to use unsigned types for unsigned quantities - + * however, these helpers are used in disk accounting calculations run by + * triggers where the output will be negated and added to an s64. unsigned is + * right out even though all these quantities will fit in 32 bits, since it + * won't be sign extended correctly; u64 will negate "correctly", but s64 is the + * simpler option here. + */ static inline s64 bch2_bucket_sectors_total(struct bch_alloc_v4 a) { return a.stripe_sectors + a.dirty_sectors + a.cached_sectors; |