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block: loop: introduce ioctl command of LOOP_SET_DIRECT_IO

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If loop block is mounted via 'mount -o loop', it isn't easy
to pass file descriptor opened as O_DIRECT, so this patch
introduces a new command to support direct IO for this case.

Cc: [email protected]
Signed-off-by: Ming Lei <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Ming Lei authored and Jens Axboe committed 2015-09-23 11:01:16 -06:00
1 parent 2e5ab5f379
commit ab1cb278bc
2 files changed
+20
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drivers/block/loop.c
+19
View File
@@ -1228,6 +1228,20 @@ static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
}
static int loop_set_dio(struct loop_device *lo, unsigned long arg)
{
int error = -ENXIO;
if (lo->lo_state != Lo_bound)
goto out;
__loop_update_dio(lo, !!arg);
if (lo->use_dio == !!arg)
return 0;
error = -EINVAL;
out:
return error;
}
static int lo_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
@@ -1271,6 +1285,11 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
err = loop_set_capacity(lo, bdev);
break;
case LOOP_SET_DIRECT_IO:
err = -EPERM;
if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
err = loop_set_dio(lo, arg);
break;
default:
err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
}
include/uapi/linux/loop.h
+1
View File
@@ -87,6 +87,7 @@ struct loop_info64 {
#define LOOP_GET_STATUS64 0x4C05
#define LOOP_CHANGE_FD 0x4C06
#define LOOP_SET_CAPACITY 0x4C07
#define LOOP_SET_DIRECT_IO 0x4C08
/* /dev/loop-control interface */
#define LOOP_CTL_ADD 0x4C80