On Wed, 2013-02-20 at 22:24 -0800, Andy Grover wrote:
> On 02/20/2013 09:57 PM, Asias He wrote:
> > This patch adds support for emulation of WRITE_SAME w/ UNMAP=1 within
> > fd_execute_write_same_unmap() backend code.
> >
> > If the FILEIO backend is normal file, the emulation uses fallocate to
> > punch hole to reclaim the free space used by the file. If the FILEIO
> > backend is block device, the emulation uses blkdev_issue_discard().
> >
> > Tested with 512, 1k, 2k, and 4k block_sizes.
>
> > + if (S_ISBLK(inode->i_mode)) {
> > + /* The backend is block device, use discard */
> > + struct block_device *bdev = inode->i_bdev;
> > +
> > + ret = blkdev_issue_discard(bdev, cmd->t_task_lba,
> > + nolb, GFP_KERNEL, 0);
> > + if (ret < 0) {
> > + pr_warn("FILEIO: blkdev_issue_discard() failed: %d\n",
> > + ret);
> > + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> > + }
> > + } else {
>
> Nothing wrong with this patch as far as I can see... but I'd like to
> reiterate my belief that we'd probably be happier if the fileio backend
> didn't also support block devices.
>
Not exactly. Some people still want/need buffered FILEIO access to an
underlying block_device for performance reasons. Given that there is no
functional equivalent with IBLOCK, dis-allowing struct block_device
export via FILEIO is not an option.
--nab
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