From f6970ad31d42fceb38b5595cbad093a4d0bfcc43 Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@linux-iscsi.org>
Date: Wed, 7 Nov 2012 20:08:38 -0800
Subject: [PATCH] target/iblock: Add WRITE_SAME w/ UNMAP=0 emulation support

This patch adds support for emulation of WRITE_SAME w/ UNMAP=0 within
iblock_execute_write_same() backend code.

The emulation uses a bio_add_page() call for each sector, and by default
enforces a limit of max_write_same_len=0xFFFF (65536) sectors following
what scsi_debug reports per default for MAXIMUM WRITE SAME LENGTH.

It also sets max_write_same_len to the operational default at setup ->
iblock_configure_device() time.

(hch: Move unmap logic into iblock_execute_write_same_unmap + add
      check for single sector SGLs in iblock_execute_write_same)
(mkp: Update comment for 0xFFFF magic constant)
(nab: drop left-over max_write_same_len check in iblock_execute_write_same)

Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
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