[dm-devel] [PATCH v2 3/3] block: implement (some of) fallocate for block devices

[Darrick J. Wong]

On Thu, Sep 29, 2016 at 01:08:57PM -0700, Bart Van Assche wrote:
> On 09/28/2016 07:19 PM, Darrick J. Wong wrote:
> >After much discussion, it seems that the fallocate feature flag
> >FALLOC_FL_ZERO_RANGE maps nicely to SCSI WRITE SAME; and the feature
> >FALLOC_FL_PUNCH_HOLE maps nicely to the devices that have been
> >whitelisted for zeroing SCSI UNMAP.  Punch still requires that
> >FALLOC_FL_KEEP_SIZE is set.  A length that goes past the end of the
> >device will be clamped to the device size if KEEP_SIZE is set; or will
> >return -EINVAL if not.  Both start and length must be aligned to the
> >device's logical block size.
> >
> >Since the semantics of fallocate are fairly well established already,
> >wire up the two pieces.  The other fallocate variants (collapse range,
> >insert range, and allocate blocks) are not supported.
> 
> For the FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE
> case, it's probably safer not to try to send a discard to block devices that
> do not support discard in order not to hit block driver bugs. But that's
> something we can still discuss later. Hence:

I'll just change it to check the queue flags and post a new revision.
At this point I might as well repost the whole thing to reflect the
reviewed-bys.

--D

> Reviewed-by: Bart Van Assche <bart.vanassche at sandisk.com>