Remove potentially_dirty counter from bottom volume

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>

modules/cas_cache/volume/obj_blk.h

@@ -14,18 +14,8 @@ struct casdsk_disk;
 
 struct bd_object {
 	struct casdsk_disk *dsk;
+
 	struct block_device *btm_bd;
-	/**
-	 * This denotes state of volatile write cache of the device.
-	 * This is set to true when:
-	 *  - opening the device
-	 *  - when writing to a device without FUA/FLUSH flags
-	 * This is set to false when:
-	 *  - FLUSH request is completed on device.
-	 * When it is false
-	 *  - FLUSH requests from upper layer are NOT passed to the device.
-	 */
-	atomic_t potentially_dirty;
 
 	uint32_t expobj_valid : 1;
 		/*!< Bit indicates that exported object was created */

modules/cas_cache/volume/vol_atomic_dev_bottom.c

@@ -35,7 +35,6 @@ struct cas_atomic_io {
 
 	struct cas_atomic_io *master;
 	atomic_t req_remaining;
-	atomic_t potential_dirty;
 	uint32_t count;
 
 	uint64_t addr;
@@ -463,23 +462,8 @@ static CAS_DECLARE_BLOCK_CALLBACK(cas_atomic_fire_atom, struct bio *bio,
 		goto out;
 	}
 
-	switch (atom->dir) {
+	if (atom->dir == OCF_READ && cas_atomic_rd_complete(atom))
-	case OCF_READ:
+		atom->master->error = -EIO;
-		if (cas_atomic_rd_complete(atom))
-			atom->master->error = -EIO;
-		break;
-	case OCF_WRITE:
-		if (!cas_blk_is_flush_io(atom->flags)) {
-			atomic_inc(&bdobj->potentially_dirty);
-		} else {
-			/* IO flush finished, update potential
-			 * dirty state
-			 */
-			atomic_sub(atomic_read(&atom->potential_dirty),
-				&bdobj->potentially_dirty);
-		}
-		break;
-	}
 
 out:
 	/* Free BIO, no needed any more */
@@ -858,16 +842,6 @@ void cas_atomic_submit_flush(struct ocf_io *io)
 
 	CAS_DEBUG_TRACE();
 
-	blkio->dirty = atomic_read(&bdobj->potentially_dirty);
-
-	if (!blkio->dirty) {
-		/* Didn't write anything to underlying disk;
-		 * no need to send req_flush
-		 */
-		io->end(io, 0);
-		return;
-	}
-
 	if (!q) {
 		io->end(io, -EINVAL);
 		return;
@@ -875,7 +849,6 @@ void cas_atomic_submit_flush(struct ocf_io *io)
 
 	if (!CAS_CHECK_QUEUE_FLUSH(q)) {
 		/* This block device does not support flush */
-		atomic_sub(blkio->dirty, &bdobj->potentially_dirty);
 		io->end(io, 0);
 		return;
 	}
@@ -900,7 +873,6 @@ void cas_atomic_submit_flush(struct ocf_io *io)
 
 	/* Set up specific field */
 	atom->dir = OCF_WRITE;
-	atomic_set(&atom->potential_dirty, blkio->dirty);
 
 	atom->request = cas_blk_make_request(q, atom->bio, GFP_NOIO);
 	if (IS_ERR(atom->request)) {

modules/cas_cache/volume/vol_blk_utils.h

@@ -24,7 +24,6 @@ struct blkio {
 	int error;
 	atomic_t rq_remaning;
 	atomic_t ref_counter;
-	int32_t dirty;
 	int32_t dir;
 
 	struct blk_data *data; /* IO data buffer */

modules/cas_cache/volume/vol_block_dev_bottom.c

@@ -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: