[PATCH v2 3/9] block: Simplify report zones execution

Damien Le Moal
2019-11-11T02:39:39Z

All kernel users of blkdev_report_zones() as well as applications use
through ioctl(BLKZONEREPORT) expect to potentially get less zone
descriptors than requested. As such, the use of the internal report
zones command execution loop implemented by blk_report_zones() is
not necessary and can even be harmful to performance by causing the
execution of inefficient small zones report command to service the
reminder of a requested zone array.

This patch removes blk_report_zones(), simplifying the code. Also
remove a now incorrect comment in dm_blk_report_zones().

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Javier Gonzalez <javier@javigon.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
block/blk-zoned.c | 34 +++++-----------------------------
drivers/md/dm.c | 6 ------
2 files changed, 5 insertions(+), 35 deletions(-)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 523a28d7a15c..ea4e086ba00e 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -119,31 +119,6 @@ static bool blkdev_report_zone(struct block_device *bdev, struct blk_zone *rep)
return true;
}

-static int blk_report_zones(struct gendisk *disk, sector_t sector,
- struct blk_zone *zones, unsigned int *nr_zones)
-{
- struct request_queue *q = disk->queue;
- unsigned int z = 0, n, nrz = *nr_zones;
- sector_t capacity = get_capacity(disk);
- int ret;
-
- while (z < nrz && sector < capacity) {
- n = nrz - z;
- ret = disk->fops->report_zones(disk, sector, &zones[z], &n);
- if (ret)
- return ret;
- if (!n)
- break;
- sector += blk_queue_zone_sectors(q) * n;
- z += n;
- }
-
- WARN_ON(z > *nr_zones);
- *nr_zones = z;
-
- return 0;
-}
-
/**
* blkdev_report_zones - Get zones information
* @bdev: Target block device
@@ -164,6 +139,7 @@ int blkdev_report_zones(struct block_device *bdev, sector_t sector,
struct blk_zone *zones, unsigned int *nr_zones)
{
struct request_queue *q = bdev_get_queue(bdev);
+ struct gendisk *disk = bdev->bd_disk;
unsigned int i, nrz;
int ret;

@@ -175,7 +151,7 @@ int blkdev_report_zones(struct block_device *bdev, sector_t sector,
* report_zones method. If it does not have one defined, the device
* driver has a bug. So warn about that.
*/
- if (WARN_ON_ONCE(!bdev->bd_disk->fops->report_zones))
+ if (WARN_ON_ONCE(!disk->fops->report_zones))
return -EOPNOTSUPP;

if (!*nr_zones || sector >= bdev->bd_part->nr_sects) {
@@ -185,8 +161,8 @@ int blkdev_report_zones(struct block_device *bdev, sector_t sector,

nrz = min(*nr_zones,
__blkdev_nr_zones(q, bdev->bd_part->nr_sects - sector));
- ret = blk_report_zones(bdev->bd_disk, get_start_sect(bdev) + sector,
- zones, &nrz);
+ ret = disk->fops->report_zones(disk, get_start_sect(bdev) + sector,
+ zones, &nrz);
if (ret)
return ret;

@@ -561,7 +537,7 @@ int blk_revalidate_disk_zones(struct gendisk *disk)

while (z < nr_zones) {
nrz = min(nr_zones - z, rep_nr_zones);
- ret = blk_report_zones(disk, sector, zones, &nrz);
+ ret = disk->fops->report_zones(disk, sector, zones, &nrz);
if (ret)
goto out;
if (!nrz)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index bc143c1b2333..89189c29438f 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -473,12 +473,6 @@ static int dm_blk_report_zones(struct gendisk *disk, sector_t sector,
goto out;
}

- /*
- * blkdev_report_zones() will loop and call this again to cover all the
- * zones of the target, eventually moving on to the next target.
- * So there is no need to loop here trying to fill the entire array
- * of zones.
- */
ret = tgt->type->report_zones(tgt, sector, zones, nr_zones);

out:
--
2.23.0