Dear,
Sorry to trouble you.
I noticed some code in dm-*.c like:
"
static int multipath_prepare_ioctl(struct dm_target *ti,
struct block_device **bdev, fmode_t *mode)
{
...
/*
* Only pass ioctls through if the device sizes match exactly.
*/
if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
return 1;
...
}
"
Here, return value 1 means
"ioctl is being issued against a subset of the parent bdev; require extra privileges."
(comment in dm_blk_ioctl)
I'm confused by the comment and '!=' test for multipath.
In which cases, the size of low level single device is not equal to the parent
size of multipath device?
Regards,
shenghui
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