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authorMartin K. Petersen <martin.petersen@oracle.com>2009-05-23 01:17:53 +0400
committerJens Axboe <jens.axboe@oracle.com>2009-05-23 01:22:55 +0400
commitc72758f33784e5e2a1a4bb9421ef3e6de8f9fcf3 (patch)
treea83f7540cc894caafe74db911cba3998d6a9a164 /include/linux/genhd.h
parentcd43e26f071524647e660706b784ebcbefbd2e44 (diff)
downloadlinux-c72758f33784e5e2a1a4bb9421ef3e6de8f9fcf3.tar.xz
block: Export I/O topology for block devices and partitions
To support devices with physical block sizes bigger than 512 bytes we need to ensure proper alignment. This patch adds support for exposing I/O topology characteristics as devices are stacked. logical_block_size is the smallest unit the device can address. physical_block_size indicates the smallest I/O the device can write without incurring a read-modify-write penalty. The io_min parameter is the smallest preferred I/O size reported by the device. In many cases this is the same as the physical block size. However, the io_min parameter can be scaled up when stacking (RAID5 chunk size > physical block size). The io_opt characteristic indicates the optimal I/O size reported by the device. This is usually the stripe width for arrays. The alignment_offset parameter indicates the number of bytes the start of the device/partition is offset from the device's natural alignment. Partition tools and MD/DM utilities can use this to pad their offsets so filesystems start on proper boundaries. Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'include/linux/genhd.h')
-rw-r--r--include/linux/genhd.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index a1a28caed23d..149fda264c86 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -90,6 +90,7 @@ struct disk_stats {
struct hd_struct {
sector_t start_sect;
sector_t nr_sects;
+ sector_t alignment_offset;
struct device __dev;
struct kobject *holder_dir;
int policy, partno;