[8/9] block: remove DISK_PITER_REVERSE

Commit Message

Christoph Hellwig Dec. 1, 2020, 4:54 p.m. UTC

There is good reason to iterate backwards when deleting all partitions in
del_gendisk, just like we don't in blk_drop_partitions.

Signed-off-by: Christoph Hellwig <[e-mail]>
---
 block/genhd.c         | 34 ++++------------------------------
 include/linux/genhd.h |  1 -
 2 files changed, 4 insertions(+), 31 deletions(-)

Comments

Tejun Heo Dec. 2, 2020, 11:15 p.m. UTC | #1

On Tue, Dec 01, 2020 at 05:54:23PM +0100, Christoph Hellwig wrote:
> There is good reason to iterate backwards when deleting all partitions in
> del_gendisk, just like we don't in blk_drop_partitions.
> 
> Signed-off-by: Christoph Hellwig <[e-mail]>

Yeah, I was blindly keeping the iteration order. Can't find any explicit
explanation why it was that way. The reverse iteration there goes back to
the initial git import. But yeah, I can't think of any meaningful difference
which can come out of it.

Acked-by: Tejun Heo <[e-mail]>

Thanks.

Patch

diff --git a/block/genhd.c b/block/genhd.c
index 65dba32df5474f..7730ddabebba92 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -182,24 +182,13 @@  static struct block_device *__disk_get_part(struct gendisk *disk, int partno)
 void disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
 			  unsigned int flags)
 {
-	struct disk_part_tbl *ptbl;
-
-	rcu_read_lock();
-	ptbl = rcu_dereference(disk->part_tbl);
-
 	piter->disk = disk;
 	piter->part = NULL;
-
-	if (flags & DISK_PITER_REVERSE)
-		piter->idx = ptbl->len - 1;
-	else if (flags & (DISK_PITER_INCL_PART0 | DISK_PITER_INCL_EMPTY_PART0))
+	if (flags & (DISK_PITER_INCL_PART0 | DISK_PITER_INCL_EMPTY_PART0))
 		piter->idx = 0;
 	else
 		piter->idx = 1;
-
 	piter->flags = flags;
-
-	rcu_read_unlock();
 }
 
 /**
@@ -214,7 +203,6 @@  void disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
 struct block_device *disk_part_iter_next(struct disk_part_iter *piter)
 {
 	struct disk_part_tbl *ptbl;
-	int inc, end;
 
 	/* put the last partition */
 	disk_part_iter_exit(piter);
@@ -223,21 +211,8 @@  struct block_device *disk_part_iter_next(struct disk_part_iter *piter)
 	rcu_read_lock();
 	ptbl = rcu_dereference(piter->disk->part_tbl);
 
-	/* determine iteration parameters */
-	if (piter->flags & DISK_PITER_REVERSE) {
-		inc = -1;
-		if (piter->flags & (DISK_PITER_INCL_PART0 |
-				    DISK_PITER_INCL_EMPTY_PART0))
-			end = -1;
-		else
-			end = 0;
-	} else {
-		inc = 1;
-		end = ptbl->len;
-	}
-
 	/* iterate to the next partition */
-	for (; piter->idx != end; piter->idx += inc) {
+	for (; piter->idx != ptbl->len; piter->idx += 1) {
 		struct block_device *part;
 
 		part = rcu_dereference(ptbl->part[piter->idx]);
@@ -252,7 +227,7 @@  struct block_device *disk_part_iter_next(struct disk_part_iter *piter)
 		piter->part = bdgrab(part);
 		if (!piter->part)
 			continue;
-		piter->idx += inc;
+		piter->idx += 1;
 		break;
 	}
 
@@ -776,8 +751,7 @@  void del_gendisk(struct gendisk *disk)
 	down_write(&bdev_lookup_sem);
 
 	/* invalidate stuff */
-	disk_part_iter_init(&piter, disk,
-			     DISK_PITER_INCL_EMPTY | DISK_PITER_REVERSE);
+	disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
 	while ((part = disk_part_iter_next(&piter))) {
 		invalidate_partition(part);
 		delete_partition(part);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 191f5e4ae4e93b..425956ac9315fa 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -217,7 +217,6 @@  void disk_uevent(struct gendisk *disk, enum kobject_action action);
 /*
  * Smarter partition iterator without context limits.
  */
-#define DISK_PITER_REVERSE	(1 << 0) /* iterate in the reverse direction */
 #define DISK_PITER_INCL_EMPTY	(1 << 1) /* include 0-sized parts */
 #define DISK_PITER_INCL_PART0	(1 << 2) /* include partition 0 */
 #define DISK_PITER_INCL_EMPTY_PART0 (1 << 3) /* include empty partition 0 */