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block: Initial support for data-less (or empty) barrier support

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This implements functionality to pass down or insert a barrier
in a queue, without having data attached to it. The ->prepare_flush_fn()
infrastructure from data barriers are reused to provide this
functionality.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2007-09-27 13:01:25 +02:00
parent c07e2b4129
commit bf2de6f5a4
5 changed files with 71 additions and 21 deletions
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19
include/linux/bio.h
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@ -176,13 +176,28 @@ struct bio {
#define bio_offset(bio) bio_iovec((bio))->bv_offset
#define bio_segments(bio) ((bio)->bi_vcnt - (bio)->bi_idx)
#define bio_sectors(bio) ((bio)->bi_size >> 9)
#define bio_cur_sectors(bio) (bio_iovec(bio)->bv_len >> 9)
#define bio_data(bio) (page_address(bio_page((bio))) + bio_offset((bio)))
#define bio_barrier(bio) ((bio)->bi_rw & (1 << BIO_RW_BARRIER))
#define bio_sync(bio) ((bio)->bi_rw & (1 << BIO_RW_SYNC))
#define bio_failfast(bio) ((bio)->bi_rw & (1 << BIO_RW_FAILFAST))
#define bio_rw_ahead(bio) ((bio)->bi_rw & (1 << BIO_RW_AHEAD))
#define bio_rw_meta(bio) ((bio)->bi_rw & (1 << BIO_RW_META))
#define bio_empty_barrier(bio) (bio_barrier(bio) && !(bio)->bi_size)
static inline unsigned int bio_cur_sectors(struct bio *bio)
{
if (bio->bi_vcnt)
return bio_iovec(bio)->bv_len >> 9;
return 0;
}
static inline void *bio_data(struct bio *bio)
{
if (bio->bi_vcnt)
return page_address(bio_page(bio)) + bio_offset(bio);
return NULL;
}
/*
* will die