after mounting with -o degraded: ioctl: LOOP_CLR_FD: Device or resource busy

after mounting with -o degraded: ioctl: LOOP_CLR_FD: Device or resource busy

[krzf83@gmail.com]

dd if=/dev/null of=img5 bs=1 seek=2G
dd if=/dev/null of=img6 bs=1 seek=2G
mkfs.btrfs -d raid1 -m raid1 img5 img6
losetup /dev/loop4 img5
losetup /dev/loop5 img6
btrfs device scan
mount -t btrfs /dev/loop4 dir
umount dir
losetup -d /dev/loop5
mount -t btrfs -o degraded /dev/loop4 dir
umount dir
losetup -d /dev/loop4
ioctl: LOOP_CLR_FD: Device or resource busy
mkfs.ext3 /dev/loop4
mke2fs 1.39 (29-May-2006)
/dev/loop4 is apparently in use by the system; will not make a filesystem here!

this only happens after mouting with -o degraded. loopback device is
unusable until next reboot

Re: after mounting with -o degraded: ioctl: LOOP_CLR_FD: Device or resource busy

[Ilya Dryomov]

On Tue, Jul 12, 2011 at 02:47:41AM +0200, krzf83@gmail.com  wrote:
> dd if=/dev/null of=img5 bs=1 seek=2G
> dd if=/dev/null of=img6 bs=1 seek=2G
> mkfs.btrfs -d raid1 -m raid1 img5 img6
> losetup /dev/loop4 img5
> losetup /dev/loop5 img6
> btrfs device scan
> mount -t btrfs /dev/loop4 dir
> umount dir
> losetup -d /dev/loop5
> mount -t btrfs -o degraded /dev/loop4 dir
> umount dir
> losetup -d /dev/loop4
> ioctl: LOOP_CLR_FD: Device or resource busy
> mkfs.ext3 /dev/loop4
> mke2fs 1.39 (29-May-2006)
> /dev/loop4 is apparently in use by the system; will not make a filesystem here!
> 
> this only happens after mouting with -o degraded. loopback device is
> unusable until next reboot

So mkfs.ext3 fails to open device with O_EXCL.

We are missing blk_put() call on error path.  At least once: if
btrfs_open_devices() fails (and it does if you e.g. zero out the
superblock on a raid1 fs while it's unmounted and then immediately
mount) it's caller never releases the other device(s).  If nobody else
steps up I can try to fix this in the next couple of days.

Thanks,

		Ilya

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