* [PATCH 1/2] blkdev.h: Introduce size_to_sectors hlper function
[not found] <20190430013205.1561708-1-marcos.souza.org@gmail.com>
@ 2019-04-30 1:32 ` Marcos Paulo de Souza
2019-04-30 2:50 ` Martin K. Petersen
2019-05-02 21:51 ` Elliott, Robert (Servers)
2019-04-30 1:32 ` [PATCH 2/2] null_blk: Make use of size_to_sectors helper Marcos Paulo de Souza
1 sibling, 2 replies; 5+ messages in thread
From: Marcos Paulo de Souza @ 2019-04-30 1:32 UTC (permalink / raw)
To: linux-block
Cc: Marcos Paulo de Souza, Jens Axboe, Hannes Reinecke, Omar Sandoval,
Ming Lei, Damien Le Moal, Bart Van Assche, Greg Edwards,
open list
This function takes an argument to specify the size of a block device,
in bytes, and return the number of sectors of 512 bytes.
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
---
Changes from v1:
Reworked the documentation of size_to_sectors by removing a sentence that was
explaining the size -> sectors math, which wasn't necessary given the
description prior to the example. (suggested by Chaitanya)
include/linux/blkdev.h | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 317ab30d2904..f6cfe6970756 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -871,6 +871,23 @@ static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
#define SECTOR_SIZE (1 << SECTOR_SHIFT)
#endif
+/**
+ * size_to_sectors - Convert size in bytes to number of sectors of 512 bytes
+ * @size: size in bytes to be converted to sectors
+ *
+ * Description:
+ * Kernel I/O operations are always made in "sectors". In order to set the
+ * correct number of sectors for a given number of bytes, we need to group the
+ * number of bytes in "sectors of 512 bytes" by shifting the size value by 9,
+ * which is the same than dividing the size by 512.
+ *
+ * Returns the number of sectors by the given number of bytes.
+ */
+static inline sector_t size_to_sectors(long long size)
+{
+ return size >> SECTOR_SHIFT;
+}
+
/*
* blk_rq_pos() : the current sector
* blk_rq_bytes() : bytes left in the entire request
--
2.16.4
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 2/2] null_blk: Make use of size_to_sectors helper
[not found] <20190430013205.1561708-1-marcos.souza.org@gmail.com>
2019-04-30 1:32 ` [PATCH 1/2] blkdev.h: Introduce size_to_sectors hlper function Marcos Paulo de Souza
@ 2019-04-30 1:32 ` Marcos Paulo de Souza
1 sibling, 0 replies; 5+ messages in thread
From: Marcos Paulo de Souza @ 2019-04-30 1:32 UTC (permalink / raw)
To: linux-block; +Cc: Marcos Paulo de Souza, Jens Axboe, open list
This helper tries to make the code easier to read, and unifies the code
of returning the number of sectors for a given number of bytes.
Reviewed-by : Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
---
No changes from v1.
drivers/block/null_blk_main.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index d7ac09c092f2..05f0bef54296 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -853,7 +853,7 @@ static int null_flush_cache_page(struct nullb *nullb, struct nullb_page *c_page)
dst = kmap_atomic(t_page->page);
for (i = 0; i < PAGE_SECTORS;
- i += (nullb->dev->blocksize >> SECTOR_SHIFT)) {
+ i += (size_to_sectors(nullb->dev->blocksize))) {
if (test_bit(i, c_page->bitmap)) {
offset = (i << SECTOR_SHIFT);
memcpy(dst + offset, src + offset,
@@ -957,7 +957,7 @@ static int copy_to_nullb(struct nullb *nullb, struct page *source,
null_free_sector(nullb, sector, true);
count += temp;
- sector += temp >> SECTOR_SHIFT;
+ sector += size_to_sectors(temp);
}
return 0;
}
@@ -989,7 +989,7 @@ static int copy_from_nullb(struct nullb *nullb, struct page *dest,
kunmap_atomic(dst);
count += temp;
- sector += temp >> SECTOR_SHIFT;
+ sector += size_to_sectors(temp);
}
return 0;
}
@@ -1004,7 +1004,7 @@ static void null_handle_discard(struct nullb *nullb, sector_t sector, size_t n)
null_free_sector(nullb, sector, false);
if (null_cache_active(nullb))
null_free_sector(nullb, sector, true);
- sector += temp >> SECTOR_SHIFT;
+ sector += size_to_sectors(temp);
n -= temp;
}
spin_unlock_irq(&nullb->lock);
@@ -1074,7 +1074,7 @@ static int null_handle_rq(struct nullb_cmd *cmd)
spin_unlock_irq(&nullb->lock);
return err;
}
- sector += len >> SECTOR_SHIFT;
+ sector += size_to_sectors(len);
}
spin_unlock_irq(&nullb->lock);
@@ -1109,7 +1109,7 @@ static int null_handle_bio(struct nullb_cmd *cmd)
spin_unlock_irq(&nullb->lock);
return err;
}
- sector += len >> SECTOR_SHIFT;
+ sector += size_to_sectors(len);
}
spin_unlock_irq(&nullb->lock);
return 0;
@@ -1201,7 +1201,7 @@ static blk_status_t null_handle_cmd(struct nullb_cmd *cmd)
if (dev->queue_mode == NULL_Q_BIO) {
op = bio_op(cmd->bio);
sector = cmd->bio->bi_iter.bi_sector;
- nr_sectors = cmd->bio->bi_iter.bi_size >> 9;
+ nr_sectors = size_to_sectors(cmd->bio->bi_iter.bi_size);
} else {
op = req_op(cmd->rq);
sector = blk_rq_pos(cmd->rq);
@@ -1406,7 +1406,7 @@ static void null_config_discard(struct nullb *nullb)
return;
nullb->q->limits.discard_granularity = nullb->dev->blocksize;
nullb->q->limits.discard_alignment = nullb->dev->blocksize;
- blk_queue_max_discard_sectors(nullb->q, UINT_MAX >> 9);
+ blk_queue_max_discard_sectors(nullb->q, size_to_sectors(UINT_MAX));
blk_queue_flag_set(QUEUE_FLAG_DISCARD, nullb->q);
}
@@ -1520,7 +1520,7 @@ static int null_gendisk_register(struct nullb *nullb)
if (!disk)
return -ENOMEM;
size = (sector_t)nullb->dev->size * 1024 * 1024ULL;
- set_capacity(disk, size >> 9);
+ set_capacity(disk, size_to_sectors(size));
disk->flags |= GENHD_FL_EXT_DEVT | GENHD_FL_SUPPRESS_PARTITION_INFO;
disk->major = null_major;
--
2.16.4
^ permalink raw reply related [flat|nested] 5+ messages in thread