From: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Ming Lei <ming.lei@redhat.com>, Greg Edwards <gedwards@ddn.com>,
Hannes Reinecke <hare@suse.com>,
linux-block@vger.kernel.org,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Jens Axboe <axboe@kernel.dk>,
Bart Van Assche <bvanassche@acm.org>,
Marcos Paulo de Souza <marcos.souza.org@gmail.com>,
Omar Sandoval <osandov@fb.com>,
Damien Le Moal <damien.lemoal@wdc.com>
Subject: [RFC PATCH 1/2] blkdev.h: Introduce size_to_sectors hlper function
Date: Sun, 21 Apr 2019 00:53:27 -0300 [thread overview]
Message-ID: <20190421035328.19322-2-marcos.souza.org@gmail.com> (raw)
In-Reply-To: <20190421035328.19322-1-marcos.souza.org@gmail.com>
This function takes an argument to specify the size of a block device,
in bytes, and return the number of sectors of 512 bytes.
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
---
include/linux/blkdev.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 317ab30d2904..7bf7b99161b7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -871,6 +871,24 @@ 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 operation 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. For example, for a capacity
+ * of 32M (33554432 bytes), the number of sectors will be 65536.
+ *
+ * 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
next prev parent reply other threads:[~2019-04-21 3:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-21 3:53 [RFC PATCH 0/2] Introduce size_to_sectors helper in blkdev.h Marcos Paulo de Souza
2019-04-21 3:53 ` Marcos Paulo de Souza [this message]
2019-04-21 17:39 ` [RFC PATCH 1/2] blkdev.h: Introduce size_to_sectors hlper function Chaitanya Kulkarni
2019-04-21 3:53 ` [RFC PATCH 2/2] null_blk: Make use of size_to_sectors helper Marcos Paulo de Souza
2019-04-21 17:42 ` Chaitanya Kulkarni
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