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

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

View File

@ -712,6 +712,14 @@ struct request *elv_next_request(struct request_queue *q)
int ret;
while ((rq = __elv_next_request(q)) != NULL) {
/*
* Kill the empty barrier place holder, the driver must
* not ever see it.
*/
if (blk_empty_barrier(rq)) {
end_queued_request(rq, 1);
continue;
}
if (!(rq->cmd_flags & REQ_STARTED)) {
/*
* This is the first time the device driver

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@ -458,9 +458,12 @@ static inline struct request *start_ordered(struct request_queue *q,
* Queue ordered sequence. As we stack them at the head, we
* need to queue in reverse order. Note that we rely on that
* no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
* request gets inbetween ordered sequence.
* request gets inbetween ordered sequence. If this request is
* an empty barrier, we don't need to do a postflush ever since
* there will be no data written between the pre and post flush.
* Hence a single flush will suffice.
*/
if (q->ordered & QUEUE_ORDERED_POSTFLUSH)
if ((q->ordered & QUEUE_ORDERED_POSTFLUSH) && !blk_empty_barrier(rq))
queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
else
q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
@ -484,7 +487,7 @@ static inline struct request *start_ordered(struct request_queue *q,
int blk_do_ordered(struct request_queue *q, struct request **rqp)
{
struct request *rq = *rqp;
int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
if (!q->ordseq) {
if (!is_barrier)
@ -3054,7 +3057,7 @@ static inline void blk_partition_remap(struct bio *bio)
{
struct block_device *bdev = bio->bi_bdev;
if (bdev != bdev->bd_contains) {
if (bio_sectors(bio) && bdev != bdev->bd_contains) {
struct hd_struct *p = bdev->bd_part;
const int rw = bio_data_dir(bio);
@ -3313,23 +3316,32 @@ void submit_bio(int rw, struct bio *bio)
{
int count = bio_sectors(bio);
BIO_BUG_ON(!bio->bi_size);
BIO_BUG_ON(!bio->bi_io_vec);
bio->bi_rw |= rw;
if (rw & WRITE) {
count_vm_events(PGPGOUT, count);
} else {
task_io_account_read(bio->bi_size);
count_vm_events(PGPGIN, count);
}
if (unlikely(block_dump)) {
char b[BDEVNAME_SIZE];
printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
current->comm, current->pid,
(rw & WRITE) ? "WRITE" : "READ",
(unsigned long long)bio->bi_sector,
bdevname(bio->bi_bdev,b));
/*
* If it's a regular read/write or a barrier with data attached,
* go through the normal accounting stuff before submission.
*/
if (!bio_empty_barrier(bio)) {
BIO_BUG_ON(!bio->bi_size);
BIO_BUG_ON(!bio->bi_io_vec);
if (rw & WRITE) {
count_vm_events(PGPGOUT, count);
} else {
task_io_account_read(bio->bi_size);
count_vm_events(PGPGIN, count);
}
if (unlikely(block_dump)) {
char b[BDEVNAME_SIZE];
printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
current->comm, current->pid,
(rw & WRITE) ? "WRITE" : "READ",
(unsigned long long)bio->bi_sector,
bdevname(bio->bi_bdev,b));
}
}
generic_make_request(bio);
@ -3405,6 +3417,14 @@ static int __end_that_request_first(struct request *req, int uptodate,
while ((bio = req->bio) != NULL) {
int nbytes;
/*
* For an empty barrier request, the low level driver must
* store a potential error location in ->sector. We pass
* that back up in ->bi_sector.
*/
if (blk_empty_barrier(req))
bio->bi_sector = req->sector;
if (nr_bytes >= bio->bi_size) {
req->bio = bio->bi_next;
nbytes = bio->bi_size;

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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

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@ -540,6 +540,7 @@ enum {
#define blk_barrier_rq(rq) ((rq)->cmd_flags & REQ_HARDBARRIER)
#define blk_fua_rq(rq) ((rq)->cmd_flags & REQ_FUA)
#define blk_bidi_rq(rq) ((rq)->next_rq != NULL)
#define blk_empty_barrier(rq) (blk_barrier_rq(rq) && blk_fs_request(rq) && !(rq)->hard_nr_sectors)
#define list_entry_rq(ptr) list_entry((ptr), struct request, queuelist)

View File

@ -264,6 +264,12 @@ void blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
{
mempool_t *pool;
/*
* Data-less bio, nothing to bounce
*/
if (bio_empty_barrier(*bio_orig))
return;
/*
* for non-isa bounce case, just check if the bounce pfn is equal
* to or bigger than the highest pfn in the system -- in that case,