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    SubjectRe: Bug in BLKBSZSET/GET ioctl ?
    On Thu, Dec 29, 2011 at 12:28:44PM +0800, Wanlong Gao wrote:
    > On 12/29/2011 12:20 PM, Wu Fengguang wrote:
    >
    > > On Thu, Dec 29, 2011 at 11:51:45AM +0800, Wanlong Gao wrote:
    > >> Hi all:
    > >>
    > >> This is first reported to *libguestfs*: https://bugzilla.redhat.com/show_bug.cgi?id=624335
    > >>
    > >> Then, I looked into upstream util-linux and it seems nothing wrong. I'm not convinced that it's a kernel bug.
    > >>
    > >> produce:
    > >>
    > >> ---
    > >> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
    > >> 4096
    > >> # ./util-linux/disk-utils/blockdev --setbsz 2048 /dev/sda6
    > >> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
    > >> 4096
    > >> # ./util-linux/disk-utils/blockdev --setbsz 512 /dev/sda6
    > >> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
    > >> 4096
    > >
    > > I think each blockdev invocation is working on a *new* bdev object.
    >
    >
    > But the address of *new* bdev is the same?
    > I did printk, and they all returned the same address.

    Then the block size value should be reset in one of the bd_set_size()
    calls in __blkdev_get().

    > > You'll get consistent results if somehow keep it referenced, for
    >
    >
    > But isn't it a bug? It seems that the setbsz has no effect?

    Yeah, it does look like unexpected behavior to the end user..

    Thanks,
    Fengguang


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