path: root/Documentation
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authorLinus Torvalds <torvalds@linux-foundation.org>2016-03-22 12:41:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-22 12:41:14 -0700
commit5266e5b12c8b73587130325f7074d2f49ef9e427 (patch)
tree79abfbf1b047de05860fa832f66fce5078cc6434 /Documentation
parentMerge tag 'pci-v4.6-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci (diff)
parenttarget: Fix target_release_cmd_kref shutdown comp leak (diff)
Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending
Pull SCSI target updates from Nicholas Bellinger: "The highlights this round include: - Add target_alloc_session() w/ callback helper for doing se_session allocation + tag + se_node_acl lookup. (HCH + nab) - Tree-wide fabric driver conversion to use target_alloc_session() - Convert sbp-target to use percpu_ida tag pre-allocation, and TARGET_SCF_ACK_KREF I/O krefs (Chris Boot + nab) - Convert usb-gadget to use percpu_ida tag pre-allocation, and TARGET_SCF_ACK_KREF I/O krefs (Andrzej Pietrasiewicz + nab) - Convert xen-scsiback to use percpu_ida tag pre-allocation, and TARGET_SCF_ACK_KREF I/O krefs (Juergen Gross + nab) - Convert tcm_fc to use TARGET_SCF_ACK_KREF I/O + TMR krefs - Convert ib_srpt to use percpu_ida tag pre-allocation - Add DebugFS node for qla2xxx target sess list (Quinn) - Rework iser-target connection termination (Jenny + Sagi) - Convert iser-target to new CQ API (HCH) - Add pass-through WRITE_SAME support for IBLOCK (Mike Christie) - Introduce data_bitmap for asynchronous access of data area (Sheng Yang + Andy) - Fix target_release_cmd_kref shutdown comp leak (Himanshu Madhani) Also, there is a separate PULL request coming for cxgb4 NIC driver prerequisites for supporting hw iscsi segmentation offload (ISO), that will be the base for a number of v4.7 developments involving iscsi-target hw offloads" * 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending: (36 commits) target: Fix target_release_cmd_kref shutdown comp leak target: Avoid DataIN transfers for non-GOOD SAM status target/user: Report capability of handling out-of-order completions to userspace target/user: Fix size_t format-spec build warning target/user: Don't free expired command when time out target/user: Introduce data_bitmap, replace data_length/data_head/data_tail target/user: Free data ring in unified function target/user: Use iovec[] to describe continuous area target: Remove enum transport_lunflags_table target/iblock: pass WRITE_SAME to device if possible iser-target: Kill the ->isert_cmd back pointer in struct iser_tx_desc iser-target: Kill struct isert_rdma_wr iser-target: Convert to new CQ API iser-target: Split and properly type the login buffer iser-target: Remove ISER_RECV_DATA_SEG_LEN iser-target: Remove impossible condition from isert_wait_conn iser-target: Remove redundant wait in release_conn iser-target: Rework connection termination iser-target: Separate flows for np listeners and connections cma events iser-target: Add new state ISER_CONN_BOUND to isert_conn ...
Diffstat (limited to 'Documentation')
1 files changed, 10 insertions, 1 deletions
diff --git a/Documentation/target/tcmu-design.txt b/Documentation/target/tcmu-design.txt
index bef81e42788f..4cebc1ebf99a 100644
--- a/Documentation/target/tcmu-design.txt
+++ b/Documentation/target/tcmu-design.txt
@@ -117,7 +117,9 @@ userspace (respectively) to put commands on the ring, and indicate
when the commands are completed.
version - 1 (userspace should abort if otherwise)
-flags - none yet defined.
+- TCMU_MAILBOX_FLAG_CAP_OOOC: indicates out-of-order completion is
+ supported. See "The Command Ring" for details.
cmdr_off - The offset of the start of the command ring from the start
of the memory region, to account for the mailbox size.
cmdr_size - The size of the command ring. This does *not* need to be a
@@ -162,6 +164,13 @@ rsp.sense_buffer if necessary. Userspace then increments
mailbox.cmd_tail by entry.hdr.length (mod cmdr_size) and signals the
kernel via the UIO method, a 4-byte write to the file descriptor.
+If TCMU_MAILBOX_FLAG_CAP_OOOC is set for mailbox->flags, kernel is
+capable of handling out-of-order completions. In this case, userspace can
+handle command in different order other than original. Since kernel would
+still process the commands in the same order it appeared in the command
+ring, userspace need to update the cmd->id when completing the
+command(a.k.a steal the original command's entry).
When the opcode is PAD, userspace only updates cmd_tail as above --
it's a no-op. (The kernel inserts PAD entries to ensure each CMD entry
is contiguous within the command ring.)