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Remove potentially_dirty counter from bottom volume

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This counter is not accurate (missing required memory barrier
to avoid unwanted behavior due to processor optimizations)
and performance gain is not clear - generally global
atomic variables are something we would like to avoid
going forward.

Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>
This commit is contained in:
Adam Rutkowski
2020-09-28 14:14:22 +02:00
parent 3ea056eb30
commit 7905ca79fa
4 changed files with 3 additions and 73 deletions
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31
modules/cas_cache/volume/vol_block_dev_bottom.c
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@@ -218,23 +218,6 @@ CAS_DECLARE_BLOCK_CALLBACK(cas_bd_io_end, struct bio *bio,
CAS_DEBUG_TRACE();
if (err)
goto out;
if (bdio->dir == OCF_WRITE) {
/* IO was a write */
if (!cas_blk_is_flush_io(io->flags)) {
/* Device cache is dirty, mark it */
atomic_inc(&bdobj->potentially_dirty);
} else {
/* IO flush finished, update potential
* dirty state
*/
atomic_sub(bdio->dirty, &bdobj->potentially_dirty);
}
}
out:
if (err == -EOPNOTSUPP && (CAS_BIO_OP_FLAGS(bio) & CAS_BIO_DISCARD))
err = 0;
@@ -253,21 +236,12 @@ static void block_dev_submit_flush(struct ocf_io *io)
struct request_queue *q = bdev_get_queue(bdev);
struct bio *bio = NULL;
blkio->dirty = atomic_read(&bdobj->potentially_dirty);
/* Prevent races of completing IO */
atomic_set(&blkio->rq_remaning, 1);
/* Increase IO reference counter for FLUSH IO */
ocf_io_get(io);
if (!blkio->dirty) {
/* Didn't write anything to underlying disk; no need to
* send req_flush
*/
goto out;
}
if (q == NULL) {
/* No queue, error */
blkio->error = -EINVAL;
@@ -276,7 +250,6 @@ static void block_dev_submit_flush(struct ocf_io *io)
if (!CAS_CHECK_QUEUE_FLUSH(q)) {
/* This block device does not support flush, call back */
atomic_sub(blkio->dirty, &bdobj->potentially_dirty);
goto out;
}
@@ -396,14 +369,10 @@ out:
static inline bool cas_bd_io_prepare(int *dir, struct ocf_io *io)
{
struct blkio *bdio = cas_io_to_blkio(io);
struct bd_object *bdobj = bd_object(ocf_io_get_volume(io));
/* Setup DIR */
bdio->dir = *dir;
/* Save dirty counter */
bdio->dirty = atomic_read(&bdobj->potentially_dirty);
/* Convert CAS direction into kernel values */
switch (bdio->dir) {
case OCF_READ: