[PATCH v4 1/5] dm: introduce flush_pass_around flag

[Yang Yang]

introduce a per-target bit "flush_pass_around" and means that the
target supports flush optimization.
set a per-table "flush_pass_around" bit if all the targets in the
table have "flush_pass_around" set.

Signed-off-by: Yang Yang <yang.yang@xxxxxxxx>
---
 drivers/md/dm-core.h          | 3 +++
 drivers/md/dm-ioctl.c         | 4 ++++
 drivers/md/dm-table.c         | 3 +++
 include/linux/device-mapper.h | 5 +++++
 4 files changed, 15 insertions(+)

diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index e6757a30dcca..b273f25b634d 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -208,6 +208,9 @@ struct dm_table {
 	bool singleton:1;
 	unsigned integrity_added:1;
 
+	/* set if all the targets in the table have "flush_pass_around" set */
+	bool flush_pass_around:1;
+
 	/*
 	 * Indicates the rw permissions for the new logical device.  This
 	 * should be a combination of BLK_OPEN_READ and BLK_OPEN_WRITE.
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index c2c07bfa6471..bb178df2a340 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1445,6 +1445,8 @@ static int populate_table(struct dm_table *table,
 		return -EINVAL;
 	}
 
+	table->flush_pass_around = 1;
+
 	for (i = 0; i < param->target_count; i++) {
 		const char *nul_terminator;
 
@@ -2279,6 +2281,8 @@ int __init dm_early_create(struct dm_ioctl *dmi,
 	if (r)
 		goto err_hash_remove;
 
+	t->flush_pass_around = 1;
+
 	/* add targets */
 	for (i = 0; i < dmi->target_count; i++) {
 		r = dm_table_add_target(t, spec_array[i]->target_type,
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 41f1d731ae5a..bd68af10afed 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -738,6 +738,9 @@ int dm_table_add_target(struct dm_table *t, const char *type,
 	if (ti->limit_swap_bios && !static_key_enabled(&swap_bios_enabled.key))
 		static_branch_enable(&swap_bios_enabled);
 
+	if (ti->flush_pass_around == 0)
+		t->flush_pass_around = 0;
+
 	return 0;
 
  bad:
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 82b2195efaca..0893ff8c01b6 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -397,6 +397,11 @@ struct dm_target {
 	 * bio_set_dev(). NOTE: ideally a target should _not_ need this.
 	 */
 	bool needs_bio_set_dev:1;
+
+	/*
+	 * Set if the target supports flush optimization
+	 */
+	bool flush_pass_around:1;
 };
 
 void *dm_per_bio_data(struct bio *bio, size_t data_size);
-- 
2.34.1