Hi!
> > How to reproduce:
> >
> > 1. make sure /tmp is mounted as tmpfs
> > 2. dd if=/dev/zero of=/tmp/disk.img bs=1M count=100
> > 3. losetup /dev/loop0 /tmp/disk.img
> > 4. mkfs.ext2 /dev/loop0
> > 5. dmesg |tail
>
> Can you wire this up for blktests?
Will try.
> > + if (ret == -EOPNOTSUPP) {
> > + struct queue_limits lim = queue_limits_start_update(lo->lo_queue);
> > +
> > + if (mode & FALLOC_FL_ZERO_RANGE)
> > + lim.max_write_zeroes_sectors = 0;
> > +
> > + if (mode & FALLOC_FL_PUNCH_HOLE) {
> > + lim.max_hw_discard_sectors = 0;
> > + lim.discard_granularity = 0;
> > + }
> > +
> > + queue_limits_commit_update(lo->lo_queue, &lim);
>
> Please split this out into a separate helper to keep it out of the
> main fast path I/O handling. A little comment that we are
> optimistically trying these if ->fallocate is support and might have
> to paddle back here would also be useful.
Will do.
Do we need noinline attribute for the function as well or unlikely() in
the if condition?
> (and maybe one day we figure out a way for the file system to
> advertise what fallocate modes it actually supports..)
One of my ideas was to try fallocate() with zero size in the
loop_reconfigure_limits() to see if we get EOPNOTSUPP but for that to
work we would have to make sure that we do not bail early on zero size
in the vfs layer...
--
Cyril Hrubis
chrubis@xxxxxxx
