Commit 90b211fa authored by Kent Overstreet's avatar Kent Overstreet
Browse files

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: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent 7442b5cd

fs/bcachefs/alloc_background.h

+8 −0
Original line number Diff line number Diff line
@@ -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;