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Correct bioq_disksort so that bioq_insert_tail() offers barrier semantic.

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Add the BIO_ORDERED flag for struct bio and update bio clients to use it.

The barrier semantics of bioq_insert_tail() were broken in two ways:

 o In bioq_disksort(), an added bio could be inserted at the head of
   the queue, even when a barrier was present, if the sort key for
   the new entry was less than that of the last queued barrier bio.

 o The last_offset used to generate the sort key for newly queued bios
   did not stay at the position of the barrier until either the
   barrier was de-queued, or a new barrier (which updates last_offset)
   was queued.  When a barrier is in effect, we know that the disk
   will pass through the barrier position just before the
   "blocked bios" are released, so using the barrier's offset for
   last_offset is the optimal choice.

sys/geom/sched/subr_disk.c:
sys/kern/subr_disk.c:
	o Update last_offset in bioq_insert_tail().

	o Only update last_offset in bioq_remove() if the removed bio is
	  at the head of the queue (typically due to a call via
	  bioq_takefirst()) and no barrier is active.

	o In bioq_disksort(), if we have a barrier (insert_point is non-NULL),
	  set prev to the barrier and cur to it's next element.  Now that
	  last_offset is kept at the barrier position, this change isn't
	  strictly necessary, but since we have to take a decision branch
	  anyway, it does avoid one, no-op, loop iteration in the while
	  loop that immediately follows.

	o In bioq_disksort(), bypass the normal sort for bios with the
	  BIO_ORDERED attribute and instead insert them into the queue
	  with bioq_insert_tail().  bioq_insert_tail() not only gives
	  the desired command order during insertion, but also provides
	  barrier semantics so that commands disksorted in the future
	  cannot pass the just enqueued transaction.

sys/sys/bio.h:
	Add BIO_ORDERED as bit 4 of the bio_flags field in struct bio.

sys/cam/ata/ata_da.c:
sys/cam/scsi/scsi_da.c
	Use an ordered command for SCSI/ATA-NCQ commands issued in
	response to bios with the BIO_ORDERED flag set.

sys/cam/scsi/scsi_da.c
	Use an ordered tag when issuing a synchronize cache command.

	Wrap some lines to 80 columns.

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
sys/geom/geom_io.c
	Mark bios with the BIO_FLUSH command as BIO_ORDERED.

Sponsored by:	Spectra Logic Corporation
MFC after:	1 month
This commit is contained in:
Justin T. Gibbs 2010-09-02 19:40:28 +00:00
parent f0092b8fc8
commit f03f7a0ca3
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=212160
7 changed files with 74 additions and 27 deletions
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3
sys/cam/ata/ata_da.c
View File

@ -874,7 +874,8 @@ adastart(struct cam_periph *periph, union ccb *start_ccb)
}
bioq_remove(&softc->bio_queue, bp);
if ((softc->flags & ADA_FLAG_NEED_OTAG) != 0) {
if ((bp->bio_flags & BIO_ORDERED) != 0
|| (softc->flags & ADA_FLAG_NEED_OTAG) != 0) {
softc->flags &= ~ADA_FLAG_NEED_OTAG;
softc->ordered_tag_count++;
tag_code = 0;

21
sys/cam/scsi/scsi_da.c
View File

@ -1354,7 +1354,8 @@ dastart(struct cam_periph *periph, union ccb *start_ccb)
bioq_remove(&softc->bio_queue, bp);
if ((softc->flags & DA_FLAG_NEED_OTAG) != 0) {
if ((bp->bio_flags & BIO_ORDERED) != 0
|| (softc->flags & DA_FLAG_NEED_OTAG) != 0) {
softc->flags &= ~DA_FLAG_NEED_OTAG;
softc->ordered_tag_count++;
tag_code = MSG_ORDERED_Q_TAG;
@ -1368,7 +1369,8 @@ dastart(struct cam_periph *periph, union ccb *start_ccb)
/*retries*/da_retry_count,
/*cbfcnp*/dadone,
/*tag_action*/tag_code,
/*read_op*/bp->bio_cmd == BIO_READ,
/*read_op*/bp->bio_cmd
== BIO_READ,
/*byte2*/0,
softc->minimum_cmd_size,
/*lba*/bp->bio_pblkno,
@ -1377,17 +1379,24 @@ dastart(struct cam_periph *periph, union ccb *start_ccb)
/*data_ptr*/ bp->bio_data,
/*dxfer_len*/ bp->bio_bcount,
/*sense_len*/SSD_FULL_SIZE,
/*timeout*/da_default_timeout*1000);
da_default_timeout * 1000);
break;
case BIO_FLUSH:
/*
* BIO_FLUSH doesn't currently communicate
* range data, so we synchronize the cache
* over the whole disk. We also force
* ordered tag semantics the flush applies
* to all previously queued I/O.
*/
scsi_synchronize_cache(&start_ccb->csio,
/*retries*/1,
/*cbfcnp*/dadone,
MSG_SIMPLE_Q_TAG,
/*begin_lba*/0,/* Cover the whole disk */
MSG_ORDERED_Q_TAG,
/*begin_lba*/0,
/*lb_count*/0,
SSD_FULL_SIZE,
/*timeout*/da_default_timeout*1000);
da_default_timeout*1000);
break;
}
start_ccb->ccb_h.ccb_state = DA_CCB_BUFFER_IO;

1
sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
View File

@ -598,6 +598,7 @@ vdev_geom_io_start(zio_t *zio)
break;
case ZIO_TYPE_IOCTL:
bp->bio_cmd = BIO_FLUSH;
bp->bio_flags |= BIO_ORDERED;
bp->bio_data = NULL;
bp->bio_offset = cp->provider->mediasize;
bp->bio_length = 0;

1
sys/geom/geom_io.c
View File

@ -265,6 +265,7 @@ g_io_flush(struct g_consumer *cp)
g_trace(G_T_BIO, "bio_flush(%s)", cp->provider->name);
bp = g_alloc_bio();
bp->bio_cmd = BIO_FLUSH;
bp->bio_flags |= BIO_ORDERED;
bp->bio_done = NULL;
bp->bio_attribute = NULL;
bp->bio_offset = cp->provider->mediasize;

37
sys/geom/sched/subr_disk.c
View File

@ -86,7 +86,7 @@ __FBSDID("$FreeBSD$");
* bioq_remove() remove a generic element from the queue, act as
* bioq_takefirst() if invoked on the head of the queue.
*
* The semantic of these methods is the same of the operations
* The semantic of these methods is the same as the operations
* on the underlying TAILQ, but with additional guarantees on
* subsequent bioq_disksort() calls. E.g. bioq_insert_tail()
* can be useful for making sure that all previous ops are flushed
@ -115,10 +115,10 @@ void
gs_bioq_remove(struct bio_queue_head *head, struct bio *bp)
{
if (bp == TAILQ_FIRST(&head->queue))
head->last_offset = bp->bio_offset + bp->bio_length;
if (bp == head->insert_point)
if (head->insert_point == NULL) {
if (bp == TAILQ_FIRST(&head->queue))
head->last_offset = bp->bio_offset + bp->bio_length;
} else if (bp == head->insert_point)
head->insert_point = NULL;
TAILQ_REMOVE(&head->queue, bp, bio_queue);
@ -137,7 +137,8 @@ void
gs_bioq_insert_head(struct bio_queue_head *head, struct bio *bp)
{
head->last_offset = bp->bio_offset;
if (head->insert_point == NULL)
head->last_offset = bp->bio_offset;
TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue);
}
@ -147,6 +148,7 @@ gs_bioq_insert_tail(struct bio_queue_head *head, struct bio *bp)
TAILQ_INSERT_TAIL(&head->queue, bp, bio_queue);
head->insert_point = bp;
head->last_offset = bp->bio_offset;
}
struct bio *
@ -189,13 +191,28 @@ gs_bioq_bio_key(struct bio_queue_head *head, struct bio *bp)
void
gs_bioq_disksort(struct bio_queue_head *head, struct bio *bp)
{
struct bio *cur, *prev = NULL;
uoff_t key = gs_bioq_bio_key(head, bp);
struct bio *cur, *prev;
uoff_t key;
if ((bp->bio_flags & BIO_ORDERED) != 0) {
/*
* Ordered transactions can only be dispatched
* after any currently queued transactions. They
* also have barrier semantics - no transactions
* queued in the future can pass them.
*/
gs_bioq_insert_tail(head, bp);
return;
}
prev = NULL;
key = gs_bioq_bio_key(head, bp);
cur = TAILQ_FIRST(&head->queue);
if (head->insert_point)
cur = head->insert_point;
if (head->insert_point) {
prev = head->insert_point;
cur = TAILQ_NEXT(head->insert_point, bio_queue);
}
while (cur != NULL && key >= gs_bioq_bio_key(head, cur)) {
prev = cur;

37
sys/kern/subr_disk.c
View File

@ -127,7 +127,7 @@ disk_err(struct bio *bp, const char *what, int blkdone, int nl)
* bioq_remove() remove a generic element from the queue, act as
* bioq_takefirst() if invoked on the head of the queue.
*
* The semantic of these methods is the same of the operations
* The semantic of these methods is the same as the operations
* on the underlying TAILQ, but with additional guarantees on
* subsequent bioq_disksort() calls. E.g. bioq_insert_tail()
* can be useful for making sure that all previous ops are flushed
@ -156,10 +156,10 @@ void
bioq_remove(struct bio_queue_head *head, struct bio *bp)
{
if (bp == TAILQ_FIRST(&head->queue))
head->last_offset = bp->bio_offset + bp->bio_length;
if (bp == head->insert_point)
if (head->insert_point == NULL) {
if (bp == TAILQ_FIRST(&head->queue))
head->last_offset = bp->bio_offset + bp->bio_length;
} else if (bp == head->insert_point)
head->insert_point = NULL;
TAILQ_REMOVE(&head->queue, bp, bio_queue);
@ -178,7 +178,8 @@ void
bioq_insert_head(struct bio_queue_head *head, struct bio *bp)
{
head->last_offset = bp->bio_offset;
if (head->insert_point == NULL)
head->last_offset = bp->bio_offset;
TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue);
}
@ -188,6 +189,7 @@ bioq_insert_tail(struct bio_queue_head *head, struct bio *bp)
TAILQ_INSERT_TAIL(&head->queue, bp, bio_queue);
head->insert_point = bp;
head->last_offset = bp->bio_offset;
}
struct bio *
@ -230,13 +232,28 @@ bioq_bio_key(struct bio_queue_head *head, struct bio *bp)
void
bioq_disksort(struct bio_queue_head *head, struct bio *bp)
{
struct bio *cur, *prev = NULL;
uoff_t key = bioq_bio_key(head, bp);
struct bio *cur, *prev;
uoff_t key;
if ((bp->bio_flags & BIO_ORDERED) != 0) {
/*
* Ordered transactions can only be dispatched
* after any currently queued transactions. They
* also have barrier semantics - no transactions
* queued in the future can pass them.
*/
bioq_insert_tail(head, bp);
return;
}
prev = NULL;
key = bioq_bio_key(head, bp);
cur = TAILQ_FIRST(&head->queue);
if (head->insert_point)
cur = head->insert_point;
if (head->insert_point) {
prev = head->insert_point;
cur = TAILQ_NEXT(head->insert_point, bio_queue);
}
while (cur != NULL && key >= bioq_bio_key(head, cur)) {
prev = cur;

1
sys/sys/bio.h
View File

@ -54,6 +54,7 @@
#define BIO_ERROR 0x01
#define BIO_DONE 0x02
#define BIO_ONQUEUE 0x04
#define BIO_ORDERED 0x08
#ifdef _KERNEL
struct disk;