[01/20] block: add ability to flag write back caching on a device

Commit Message

Jens Axboe April 13, 2016, 3:32 p.m. UTC

On Wed, Apr 13 2016, Ming Lei wrote:
> > +static ssize_t queue_wc_store(struct request_queue *q, const char *page,
> > +                             size_t count)
> > +{
> > +       int set = -1;
> > +
> > +       if (!strncmp(page, "write back", 10))
> > +               set = 1;
> > +       else if (!strncmp(page, "write through", 13) ||
> > +                !strncmp(page, "none", 4))
> > +               set = 0;
> > +
> > +       if (set == -1)
> > +               return -EINVAL;
> > +
> > +       spin_lock_irq(q->queue_lock);
> > +       if (set)
> > +               queue_flag_set(QUEUE_FLAG_WC, q);
> > +       else
> > +               queue_flag_clear(QUEUE_FLAG_WC, q);
> > +       spin_unlock_irq(q->queue_lock);
> 
> When the write cache (queue)flag is changed, I guess we need to change
> q->flush_flags via blk_queue_write_cache() too? Otherwise, the change
> on write cache flag can't affect block flush behaviour.
> 
> BTW, looks the flush_flags has been redundant after this patch, can
> we just kill it in the future?

How about we fold both those concerns into one? Kill off ->flush_flags,
and that then fixes the other part as well. Like the below, untested.

Patch

diff --git a/block/blk-core.c b/block/blk-core.c
index c50227796a26..2475b1c72773 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1964,7 +1964,8 @@  generic_make_request_checks(struct bio *bio)
 	 * drivers without flush support don't have to worry
 	 * about them.
 	 */
-	if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
+	if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) &&
+	    !test_bit(QUEUE_FLAG_WC, &q->queue_flags)) {
 		bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
 		if (!nr_sectors) {
 			err = 0;
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 9c423e53324a..b1c91d229e5e 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -95,17 +95,18 @@  enum {
 static bool blk_kick_flush(struct request_queue *q,
 			   struct blk_flush_queue *fq);
 
-static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq)
+static unsigned int blk_flush_policy(unsigned long fflags, struct request *rq)
 {
 	unsigned int policy = 0;
 
 	if (blk_rq_sectors(rq))
 		policy |= REQ_FSEQ_DATA;
 
-	if (fflags & REQ_FLUSH) {
+	if (fflags & (1UL << QUEUE_FLAG_WC)) {
 		if (rq->cmd_flags & REQ_FLUSH)
 			policy |= REQ_FSEQ_PREFLUSH;
-		if (!(fflags & REQ_FUA) && (rq->cmd_flags & REQ_FUA))
+		if (!(fflags & (1UL << QUEUE_FLAG_FUA)) &&
+		    (rq->cmd_flags & REQ_FUA))
 			policy |= REQ_FSEQ_POSTFLUSH;
 	}
 	return policy;
@@ -384,7 +385,7 @@  static void mq_flush_data_end_io(struct request *rq, int error)
 void blk_insert_flush(struct request *rq)
 {
 	struct request_queue *q = rq->q;
-	unsigned int fflags = q->flush_flags;	/* may change, cache */
+	unsigned long fflags = q->queue_flags;	/* may change, cache */
 	unsigned int policy = blk_flush_policy(fflags, rq);
 	struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx);
 
@@ -393,7 +394,7 @@  void blk_insert_flush(struct request *rq)
 	 * REQ_FLUSH and FUA for the driver.
 	 */
 	rq->cmd_flags &= ~REQ_FLUSH;
-	if (!(fflags & REQ_FUA))
+	if (!(fflags & (1UL << QUEUE_FLAG_FUA)))
 		rq->cmd_flags &= ~REQ_FUA;
 
 	/*
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 80d9327a214b..f679ae122843 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -822,7 +822,12 @@  EXPORT_SYMBOL(blk_queue_update_dma_alignment);
 
 void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
 {
-	q->flush_not_queueable = !queueable;
+	spin_lock_irq(q->queue_lock);
+	if (queueable)
+		clear_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
+	else
+		set_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
+	spin_unlock_irq(q->queue_lock);
 }
 EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
 
@@ -837,16 +842,13 @@  EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
 void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
 {
 	spin_lock_irq(q->queue_lock);
-	if (wc) {
+	if (wc)
 		queue_flag_set(QUEUE_FLAG_WC, q);
-		q->flush_flags = REQ_FLUSH;
-	} else
+	else
 		queue_flag_clear(QUEUE_FLAG_WC, q);
-	if (fua) {
-		if (wc)
-			q->flush_flags |= REQ_FUA;
+	if (fua)
 		queue_flag_set(QUEUE_FLAG_FUA, q);
-	} else
+	else
 		queue_flag_clear(QUEUE_FLAG_FUA, q);
 	spin_unlock_irq(q->queue_lock);
 }
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 26aa080e243c..3355f1cdd4e5 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -477,7 +477,7 @@  static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
 		vbd->type |= VDISK_REMOVABLE;
 
 	q = bdev_get_queue(bdev);
-	if (q && q->flush_flags)
+	if (q && test_bit(QUEUE_FLAG_WC, &q->queue_flags))
 		vbd->flush_support = true;
 
 	if (q && blk_queue_secdiscard(q))
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 4b1ffc0abe11..6817cd0bd220 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1348,13 +1348,13 @@  static void dm_table_verify_integrity(struct dm_table *t)
 static int device_flush_capable(struct dm_target *ti, struct dm_dev *dev,
 				sector_t start, sector_t len, void *data)
 {
-	unsigned flush = (*(unsigned *)data);
+	unsigned long flush = (*(unsigned *)data);
 	struct request_queue *q = bdev_get_queue(dev->bdev);
 
-	return q && (q->flush_flags & flush);
+	return q && (q->queue_flags & flush);
 }
 
-static bool dm_table_supports_flush(struct dm_table *t, unsigned flush)
+static bool dm_table_supports_flush(struct dm_table *t, unsigned long flush)
 {
 	struct dm_target *ti;
 	unsigned i = 0;
@@ -1518,9 +1518,9 @@  void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	else
 		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 
-	if (dm_table_supports_flush(t, REQ_FLUSH)) {
+	if (dm_table_supports_flush(t, (1UL << QUEUE_FLAG_WC))) {
 		wc = true;
-		if (dm_table_supports_flush(t, REQ_FUA))
+		if (dm_table_supports_flush(t, (1UL << QUEUE_FLAG_FUA)))
 			fua = true;
 	}
 	blk_queue_write_cache(q, wc, fua);
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 9531f5f05b93..7c6778c5ea38 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1188,6 +1188,7 @@  ioerr:
 
 int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
 {
+	struct request_queue *q = bdev_get_queue(rdev->bdev);
 	struct r5l_log *log;
 
 	if (PAGE_SIZE != 4096)
@@ -1197,7 +1198,7 @@  int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
 		return -ENOMEM;
 	log->rdev = rdev;
 
-	log->need_cache_flush = (rdev->bdev->bd_disk->queue->flush_flags != 0);
+	log->need_cache_flush = test_bit(QUEUE_FLAG_WC, &q->queue_flags);
 
 	log->uuid_checksum = crc32c_le(~0, rdev->mddev->uuid,
 				       sizeof(rdev->mddev->uuid));
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index 026a758e5778..5a0ec46df976 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -687,10 +687,10 @@  iblock_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 		 * Force writethrough using WRITE_FUA if a volatile write cache
 		 * is not enabled, or if initiator set the Force Unit Access bit.
 		 */
-		if (q->flush_flags & REQ_FUA) {
+		if (test_bit(QUEUE_FLAG_FUA, &q->queue_flags)) {
 			if (cmd->se_cmd_flags & SCF_FUA)
 				rw = WRITE_FUA;
-			else if (!(q->flush_flags & REQ_FLUSH))
+			else if (!test_bit(QUEUE_FLAG_FUA, &q->queue_flags))
 				rw = WRITE_FUA;
 			else
 				rw = WRITE;
@@ -836,7 +836,7 @@  static bool iblock_get_write_cache(struct se_device *dev)
 	struct block_device *bd = ib_dev->ibd_bd;
 	struct request_queue *q = bdev_get_queue(bd);
 
-	return q->flush_flags & REQ_FLUSH;
+	return test_bit(QUEUE_FLAG_WC, &queue_nq->queue_flags);
 }
 
 static const struct target_backend_ops iblock_ops = {
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f3f232fa505d..57c085917da6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -433,8 +433,6 @@  struct request_queue {
 	/*
 	 * for flush operations
 	 */
-	unsigned int		flush_flags;
-	unsigned int		flush_not_queueable:1;
 	struct blk_flush_queue	*fq;
 
 	struct list_head	requeue_list;
@@ -493,6 +491,7 @@  struct request_queue {
 #define QUEUE_FLAG_POLL	       22	/* IO polling enabled if set */
 #define QUEUE_FLAG_WC	       23	/* Write back caching */
 #define QUEUE_FLAG_FUA	       24	/* device supports FUA writes */
+#define QUEUE_FLAG_FLUSH_NQ    25	/* flush not queueuable */
 
 #define QUEUE_FLAG_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
 				 (1 << QUEUE_FLAG_STACKABLE)	|	\
@@ -1365,7 +1364,7 @@  static inline unsigned int block_size(struct block_device *bdev)
 
 static inline bool queue_flush_queueable(struct request_queue *q)
 {
-	return !q->flush_not_queueable;
+	return !test_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
 }
 
 typedef struct {struct page *v;} Sector;