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loop: add ioctl for changing logical block size 

This is a different approach from the first attempt in f2c6df7dbf
("loop: support 4k physical blocksize"). Rather than extending
LOOP_{GET,SET}_STATUS, add a separate ioctl just for setting the block
size.

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Omar Sandoval 2017-08-24 00:03:43 -07:00 committed by Jens Axboe
parent 6c6b6f28b3
commit 89e4fdecb5
2 changed files with 25 additions and 0 deletions
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24
drivers/block/loop.c
View File

@ -1047,6 +1047,7 @@ static int loop_clr_fd(struct loop_device *lo)
memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
memset(lo->lo_file_name, 0, LO_NAME_SIZE);
blk_queue_logical_block_size(lo->lo_queue, 512);
if (bdev) {
bdput(bdev);
invalidate_bdev(bdev);
@ -1330,6 +1331,24 @@ static int loop_set_dio(struct loop_device *lo, unsigned long arg)
return error;
}
static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
{
if (lo->lo_state != Lo_bound)
return -ENXIO;
if (arg < 512 || arg > PAGE_SIZE || !is_power_of_2(arg))
return -EINVAL;
blk_mq_freeze_queue(lo->lo_queue);
blk_queue_logical_block_size(lo->lo_queue, arg);
loop_update_dio(lo);
blk_mq_unfreeze_queue(lo->lo_queue);
return 0;
}
static int lo_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
@ -1378,6 +1397,11 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
err = loop_set_dio(lo, arg);
break;
case LOOP_SET_BLOCK_SIZE:
err = -EPERM;
if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
err = loop_set_block_size(lo, arg);
break;
default:
err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
}

1
include/uapi/linux/loop.h
View File

@ -88,6 +88,7 @@ struct loop_info64 {
#define LOOP_CHANGE_FD 0x4C06
#define LOOP_SET_CAPACITY 0x4C07
#define LOOP_SET_DIRECT_IO 0x4C08
#define LOOP_SET_BLOCK_SIZE 0x4C09
/* /dev/loop-control interface */
#define LOOP_CTL_ADD 0x4C80