[PATCH] loop: drop caches if offset or block_size are changed

[grygorii tertychnyi <gtertych@xxxxxxxxx>]

Jaegeuk,

We also observed an issue with this patch.

After heavely working with image.bin (haxdump with different offsets)
next mount call fails:

# mount -o ro,loop,offset=45967633 -t squashfs image.bin /tmp/gi45
mount: image.bin: failed to setup loop device: Resource temporarily unavailable

# dmesg | tail -n1
loop_set_status: loop2 () has still dirty pages (nrpages=1)


-- Grygorii