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block: shrink struct bio down to 2 cache lines again

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Commit bcf2843b3f8f added ->bi_error to cleanup the error passing
for struct bio, but that ended up adding 4 bytes and a 4 byte hole
to the size of struct bio. For a clean config, that bumped it from
128 bytes, to 136 bytes, on x86-64.

The ->bi_flags member is currently an unsigned long, but it fits
easily within an int. Change it to an unsigned int, adjust the
the pool offset code, and move ->bi_error into the new hole. Then
we end up with a 128 byte bio again.

Change the bio flag set/clear to use cmpxchg to ensure we don't
lose any flags when manipulating them.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2015-07-28 13:14:32 -06:00
parent b7c44ed9d2
commit 2c68f6dc6e
2 changed files with 6 additions and 6 deletions
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6
include/linux/bio.h
View File

@ -306,17 +306,17 @@ static inline void bio_cnt_set(struct bio *bio, unsigned int count)
static inline bool bio_flagged(struct bio *bio, unsigned int bit)
{
return (bio->bi_flags & (1UL << bit)) != 0;
return (bio->bi_flags & (1U << bit)) != 0;
}
static inline void bio_set_flag(struct bio *bio, unsigned int bit)
{
bio->bi_flags |= (1UL << bit);
bio->bi_flags |= (1U << bit);
}
static inline void bio_clear_flag(struct bio *bio, unsigned int bit)
{
bio->bi_flags &= ~(1UL << bit);
bio->bi_flags &= ~(1U << bit);
}
enum bip_flags {

6
include/linux/blk_types.h
View File

@ -46,14 +46,14 @@ struct bvec_iter {
struct bio {
struct bio *bi_next; /* request queue link */
struct block_device *bi_bdev;
unsigned long bi_flags; /* status, command, etc */
unsigned int bi_flags; /* status, command, etc */
int bi_error;
unsigned long bi_rw; /* bottom bits READ/WRITE,
* top bits priority
*/
struct bvec_iter bi_iter;
int bi_error;
/* Number of segments in this BIO after
* physical address coalescing is performed.
*/
@ -134,7 +134,7 @@ struct bio {
*/
#define BIO_POOL_BITS (4)
#define BIO_POOL_NONE ((1UL << BIO_POOL_BITS) - 1)
#define BIO_POOL_OFFSET (BITS_PER_LONG - BIO_POOL_BITS)
#define BIO_POOL_OFFSET (32 - BIO_POOL_BITS)
#define BIO_POOL_MASK (1UL << BIO_POOL_OFFSET)
#define BIO_POOL_IDX(bio) ((bio)->bi_flags >> BIO_POOL_OFFSET)