On 05/23/2017 12:27 PM, Jeff Cody wrote: > On current released versions of glusterfs, glfs_lseek() will sometimes > return invalid values for SEEK_DATA or SEEK_HOLE. For SEEK_DATA and > SEEK_HOLE, the returned value should be >= the passed offset, or < 0 in > the case of error: >
> However, occasionally glfs_lseek() for SEEK_HOLE/DATA will return a
> value less than the passed offset, yet greater than zero.
Ouch.
>
> Although this is being fixed in gluster, we still should work around it
> in QEMU, given that multiple released versions of gluster behave this
> way.
Fair enough.
>
> This patch treats the return case of (offs < start) the same as if an
> error value other than ENXIO is returned; we will assume we learned
> nothing, and there are no holes in the file.
Yes, holes are merely an optimization, so treating bugs by the
pessimistic fallback of no holes rather than aborting is reasonable.
> +++ b/block/gluster.c
> @@ -1275,7 +1275,14 @@ static int find_allocation(BlockDriverState *bs, off_t
> start,
> if (offs < 0) {
> return -errno; /* D3 or D4 */
> }
> - assert(offs >= start);
> +
> + if (offs < start) {
> + /* This is not a valid return by lseek(). We are safe to just return
> + * -EIO in this case, and we'll treat it like D4. Unfortunately some
> + * versions of libgfapi will return offs < start, so an assert here
> + * will unneccesarily abort QEMU. */
s/unneccesarily/unnecessarily/ (twice)
With spelling fix,
Reviewed-by: Eric Blake <ebl...@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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