* fast creation and deletion of loop devices
@ 2021-07-08 12:18 Simon Richter
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From: Simon Richter @ 2021-07-08 12:18 UTC (permalink / raw)
To: linux-block
Hi,
I have just used a crude loop to search for a partition on a block
device:
for i in `seq 1 4096`
do
losetup -r -o ${i}k /dev/loop0 /dev/sda
mount /dev/loop0 /mnt && break
losetup -d /dev/loop0
done
Creating the loop device fails sometimes, with
losetup: /dev/sda: failed to set up loop device: Device or resource busy
and the kernel log contains a few instances of
loop_set_status: loop0 () has still dirty pages (nrpages=5)
My machine is now in a state where I can call
until losetup -d /dev/loop0; do :; done
and the loop just keeps running.
I'm slightly confused why a read-only loop device would have dirty pages
in the first place, and I suspect that there is a kernel bug here that
allows me to enter an inconsistent state through a race condition if I
just attach and detach loop devices fast enough.
Simon
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2021-07-08 12:18 fast creation and deletion of loop devices Simon Richter
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