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target: Fix COMPARE_AND_WRITE with SG_TO_MEM_NOALLOC handling

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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>
This commit is contained in:
Nicholas Bellinger
2015-04-07 21:53:27 +00:00
parent 9ac8928e6a
commit c8e639852a
3 changed files with 44 additions and 10 deletions
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include/target/target_core_base.h
+1 -1
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@@ -523,7 +523,7 @@ struct se_cmd {
sense_reason_t (*execute_cmd)(struct se_cmd *);
sense_reason_t (*execute_rw)(struct se_cmd *, struct scatterlist *,
u32, enum dma_data_direction);
sense_reason_t (*transport_complete_callback)(struct se_cmd *);
sense_reason_t (*transport_complete_callback)(struct se_cmd *, bool);
unsigned char *t_task_cdb;
unsigned char __t_task_cdb[TCM_MAX_COMMAND_SIZE];