From: Nicholas Bellinger <nab@linux-iscsi.org>
Date: Tue, 7 Apr 2015 21:53:27 +0000 (+0000)
Subject: target: Fix COMPARE_AND_WRITE with SG_TO_MEM_NOALLOC handling
X-Git-Tag: omap-for-v4.2/o2_dc~20^2~14
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c8e639852ad720499912acedfd6b072325fd2807;p=pandora-kernel.git

target: Fix COMPARE_AND_WRITE with SG_TO_MEM_NOALLOC handling

This patch fixes a bug for COMPARE_AND_WRITE handling with
fabrics using SCF_PASSTHROUGH_SG_TO_MEM_NOALLOC.

It adds the missing allocation for cmd->t_bidi_data_sg within
transport_generic_new_cmd() that is used by COMPARE_AND_WRITE
for the initial READ payload, even if the fabric is already
providing a pre-allocated buffer for cmd->t_data_sg.

Also, fix zero-length COMPARE_AND_WRITE handling within the
compare_and_write_callback() and target_complete_ok_work()
to queue the response, skipping the initial READ.

This fixes COMPARE_AND_WRITE emulation with loopback, vhost,
and xen-backend fabric drivers using SG_TO_MEM_NOALLOC.

Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org> # v3.12+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---

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