The return value wasn't checked by any of the callers. Assuming this is
correct behaviour, we can simplify some code by not bothering to
generate it.
nab: Add srpt_queue_data_in() + srpt_queue_tm_rsp() nops around
srpt_queue_response() void return
Signed-off-by: Joern Engel <joern@logfs.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Three have been checked for but were never set. Remove the dead code.
Also renumbers the remaining ones to a) get rid of the holes after the
removal and b) avoid a collision between TMR_FUNCTION_COMPLETE==0 and
the uninitialized case. If we failed to set a code, we should rather
fall into the default case then return success.
Signed-off-by: Joern Engel <joern@logfs.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch addresses a bug where RDMA_CM_EVENT_DISCONNECTED may occur
before the connection shutdown has been completed by rx/tx threads,
that causes isert_free_conn() to wait indefinately on ->conn_wait.
This patch allows isert_disconnect_work code to invoke rdma_disconnect
when isert_disconnect_work() process context is started by client
session reset before isert_free_conn() code has been reached.
It also adds isert_conn->conn_mutex protection for ->state within
isert_disconnect_work(), isert_cq_comp_err() and isert_free_conn()
code, along with isert_check_state() for wait_event usage.
(v2: Add explicit iscsit_cause_connection_reinstatement call
during isert_disconnect_work() to force conn reset)
Cc: stable@vger.kernel.org # 3.10+
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch moves ISCSI_OP_REJECT failures into iscsit_sequence_cmd()
in order to avoid external iscsit_reject_cmd() reject usage for all
PDU types.
It also updates PDU specific handlers for traditional iscsi-target
code to not reset the session after posting a ISCSI_OP_REJECT during
setup.
(v2: Fix CMDSN_LOWER_THAN_EXP for ISCSI_OP_SCSI to call
target_put_sess_cmd() after iscsit_sequence_cmd() failure)
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch changes iscsit_add_reject() + iscsit_add_reject_from_cmd()
usage to not sleep on iscsi_cmd->reject_comp to address a free-after-use
usage bug in v3.10 with iser-target code.
It saves ->reject_reason for use within iscsit_build_reject() so the
correct value for both transport cases. It also drops the legacy
fail_conn parameter usage throughput iscsi-target code and adds
two iscsit_add_reject_cmd() and iscsit_reject_cmd helper functions,
along with various small cleanups.
(v2: Re-enable target_put_sess_cmd() to be called from
iscsit_add_reject_from_cmd() for rejects invoked after
target_get_sess_cmd() has been called)
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch adds an optional /auth/ configfs group to TPG context that
can be used by fabrics like iscsi-target for TPG demo-mode
authentication.
Cc: Dax Kelson <dkelson@gurulabs.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch refactoring existing iscsit_send_text_rsp() in order
to handle iscsi_text_rsp payloads in a transport specific manner.
This includes the addition of iscsit_build_text_rsp() to build
the response payload and initialize ISCSI_OP_TEXT_RSP.
v2: Make iscsit_build_text_rsp() determine extra padding bytes, and
drop legacy padding calculation for traditional iSCSI text
responses within iscsit_send_text_rsp()
Reported-by: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch refactors ISCSI_OP_TEXT handling within iscsi-target in
order to handle iscsi_text payloads in a transport specific manner.
This includes splitting current iscsit_handle_text_cmd() into
iscsit_setup_text_cmd() and iscsit_process_text_cmd() calls, and
makes iscsit_handle_text_cmd be only used internally by traditional
iscsi socket calls.
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch refactors ISCSI_OP_NOOP handling within iscsi-target in
order to handle iscsi_nopout payloads in a transport specific manner.
This includes splitting existing iscsit_handle_nop_out() into
iscsit_setup_nop_out() and iscsit_process_nop_out() calls, and
makes iscsit_handle_nop_out() be only used internally by traditional
iscsi socket calls.
Next update iser-target code to use new callers and add FIXME for
the handling iscsi_nopout payloads. Also fix reject response handling
in iscsit_setup_nop_out() to use proper iscsit_add_reject_from_cmd().
v2: Fix uninitialized iscsit_handle_nop_out() payload_length usage (Fengguang)
v3: Remove left-over dead code in iscsit_setup_nop_out() (DanC)
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Now with iscsi-target using modern se_cmd->cmd_kref accounting in
v3.10 code, it's safe to go ahead and drop the legacy release
codepath + se_cmd->check_release bit in transport_release_cmd()
Cc: Christoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@kernel.org>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Moussa Ba <moussaba@micron.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch removes legacy se_cmd->t_fe_count usage in order to avoid
se_cmd->t_state_lock access within transport_put_cmd() during normal
fast path se_cmd descriptor release.
Also drop the left-over parameter usage within core_tmr_handle_tas_abort()
Cc: Christoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@kernel.org>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Moussa Ba <moussaba@micron.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Instead of taking the buffer and length, update_and_write_aptpl() will
allocate the buffer as needed, and then free it. Instead, the function
takes an 'aptpl' boolean parameter.
This enables us to remove memory alloc/frees from struct
t10_pr_registration and other spots.
There is a slight loss of functionality because each callsite doesn't get
its own pr_debug any more, but this info can be cleaned via ftrace if
necessary and I think the shorter code is worth it.
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
It's only ever set to PR_APTPL_BUF_LEN, so we don't need a variable.
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Go ahead and propigate up the ->cmd_kref put return value from
target_put_sess_cmd() -> transport_release_cmd() -> transport_put_cmd()
-> transport_generic_free_cmd().
This is useful for certain fabrics when determining the active I/O
shutdown case with SCF_ACK_KREF where a final target_put_sess_cmd()
is still required by the caller.
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Switch back to pre commit 1c7b13fe65 list splicing logic for active I/O
shutdown with tcm_qla2xxx + ib_srpt fabrics.
The original commit was done under the incorrect assumption that it's safe to
walk se_sess->sess_cmd_list unprotected in target_wait_for_sess_cmds() after
sess->sess_tearing_down = 1 has been set by target_sess_cmd_list_set_waiting()
during session shutdown.
So instead of adding sess->sess_cmd_lock protection around sess->sess_cmd_list
during target_wait_for_sess_cmds(), switch back to sess->sess_wait_list to
allow wait_for_completion() + TFO->release_cmd() to occur without having to
walk ->sess_cmd_list after the list_splice.
Also add a check to exit if target_sess_cmd_list_set_waiting() has already
been called, and add a WARN_ON to check for any fabric bug where new se_cmds
are added to sess->sess_cmd_list after sess->sess_tearing_down = 1 has already
been set.
Cc: Joern Engel <joern@logfs.org>
Cc: Roland Dreier <roland@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Drop unused transport_wait_for_tasks() check in target_wait_for_sess_cmds
shutdown code, and convert tcm_qla2xxx + ib_srpt fabric drivers.
Cc: Joern Engel <joern@logfs.org>
Cc: Roland Dreier <roland@kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Some were incremented, but never used anywhere from what I could tell.
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Add basic struct iscsit_transport API template to allow iscsi-target for
running with external transport modules using existing iscsi_target_core.h
code.
For all external modules, this calls try_module_get() and module_put()
to obtain + release an external iscsit_transport module reference count.
Also include the iscsi-target symbols necessary in iscsi_transport.h to
allow external transport modules to function.
v3 changes:
- Add iscsit_build_reject export for ISTATE_SEND_REJECT usage
v2 changes:
- Drop unnecessary export of iscsit_get_transport + iscsit_put_transport (roland)
- Add ->iscsit_queue_data_in() to remove extra context switch on RDMA_WRITE
- Add ->iscsit_queue_status() to remove extra context switch on IB_SEND status
- Add ->iscsit_get_dataout() to remove extra context switch on RDMA_READ
- Drop ->iscsit_free_cmd()
- Drop ->iscsit_unmap_cmd()
- Rename iscsit_create_transport() -> iscsit_register_transport() (andy)
- Rename iscsit_destroy_transport() -> iscsit_unregister_transport() (andy)
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
iblock_execute_unmap() and fd_execute_unmap share a lot of code.
Add sbc_execute_unmap() helper to remove duplicated code for
iblock_execute_unmap() and fd_execute_unmap().
Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Trivial, but WRITE SAME is an SBC command so it seems strange for a
related function (defined in target_core_sbc.c) to be in the spc_
namespace.
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
SBC-3 (revision 35) says:
The PARAMETER LIST LENGTH field specifies the length in bytes of the
UNMAP parameter list that is available to be transferred from the
Data-Out Buffer. If the parameter list length is greater than zero
and less than 0008h (i.e., eight), then the device server shall
terminate the command with CHECK CONDITION status with the sense key
set to ILLEGAL REQUEST and the additional sense code set to
PARAMETER LIST LENGTH ERROR. A PARAMETER LIST LENGTH set to zero
specifies that no data shall be sent.
so our sense code for too-short descriptors was wrong, and we were
incorrectly failing commands that didn't transfer any descriptors.
While we're at it, also handle the UNMAP check:
If the ANCHOR bit is set to one, and the ANC_SUP bit in the Logical
Block Provisioning VPD page (see 6.6.4) is set to zero, then the
device server shall terminate the command with CHECK CONDITION
status with the sense key set to ILLEGAL REQUEST and the additional
sense code set to INVALID FIELD IN CDB.
(chris boot: Fix wrong cut+paste comment in transport_send_check_condition_and_sense)
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch changes LIO to use the configfs backend device name as the
model if you echo '1' to an individual device's emulate_model_alias attribute.
This is a valid operation only on devices with an export count of 0.
Signed-off-by: Tregaron Bayly <tbayly@bluehost.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch allows IBLOCK to check block hints in request_queue->flush_flags
when reporting current backend device WriteCacheEnabled status to a remote
SCSI initiator port.
This is done via a se_subsystem_api->get_write_cache() call instead of a
backend se_device creation time flag, as we expect REQ_FLUSH bits to possibly
change from an underlying blk_queue_flush() by the SCSI disk driver, or
internal raw struct block_device driver usage.
Also go ahead and update iblock_execute_rw() bio I/O path code to use
REQ_FLUSH + REQ_FUA hints when determining WRITE_FUA usage, and make SPC
emulation code use a spc_check_dev_wce() helper to handle both types of
cases for virtual backend subsystem drivers.
(asias: Drop unnecessary comparsion operators)
Reported-by: majianpeng <majianpeng@gmail.com>
Cc: majianpeng <majianpeng@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
"buf" is 128 characters and "vpd->device_identifier" is 256. It makes
the static checkers complain.
Also bump VPD_TMP_BUF_SIZE to match INQUIRY_VPD_DEVICE_IDENTIFIER_LEN.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Some target drivers might need to access the inquiry data
directly, without sending out the actual command.
So export these functions.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Cc: Nicholas Bellinger <nab@risingtidesystems.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Introduce TCM_NO_SENSE, mapping to sense code
'Not ready, no additional sense information'.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Cc: Nicholas Bellinger <nab@risingtidesystems.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Thanks for reviews, looking a lot better.
---- 8< ----
Initiator access config could be easier. The way other storage vendors
have addressed this is to support initiator groups: the admin adds
initiator WWNs to the group, and then LUN permissions can be granted for
the entire group at once.
Instead of changing ktarget's configfs interface, this patch keeps
the configfs interface per-initiator-wwn and just adds a 'tag' field
for each. This should be enough for user tools like targetcli to group
initiator ACLs and sync their configurations.
acl_tag is not used internally, but needs to be kept in configfs so that
all user tools can avoid dependencies on each other.
Code tested to work, although userspace pieces still to be implemented.
Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch adds [dev,lun]_link_magic value assignment + checks within generic
target_fabric_port_link() and target_fabric_mappedlun_link() code to ensure
destination config_item *target_item sent from configfs_symlink() ->
config_item_operations->allow_link() is the underlying se_device->dev_group
and se_lun->lun_group that we expect to symlink.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
We already expect TFO->get_blocks() to return sector_t for zero value case
when doing WRITE_SAME to the end of the backend device, so go ahead and return
sector_t from spc_get_write_same_sectors() to handle this case properly.
Also, update the single iblock_execute_write_same() caller of this code.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch adds a new max_write_same_len device attribute for use with
WRITE_SAME w/ UNMAP=0 backend emulation. This can be useful for
lowering the default backend value (IBLOCK uses 0xFFFF).
Also, update block limits VPD emulation code in spc_emulate_evpd_b0() to
report MAXIMUM WRITE SAME LENGTH, and enforce max_write_same_len during
sbc_parse() -> sbc_setup_write_same() CDB sanity checking for all emulated
WRITE_SAME w/ UNMAP=0 cases.
(Robert: Move max_write_same_len check in sbc_setup_write_same() to
check both WRITE_SAME w/ UNMAP=1 and w/ UNMAP=0 cases)
Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Robert Elliott <Elliott@hp.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch adds a new sbc_ops->execute_write_same_unmap() caller for use
with WRITE_SAME w/ UNMAP=1, and performs the ->execute_cmd() setup based
this bit within sbc_setup_write_same() code.
Also, makes the changes in sbc_parse_cdb() to handle a sense_reason_t
return from sbc_setup_write_same() on error.
Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Pass the sense reason as an explicit return value from the I/O submission
path instead of storing it in struct se_cmd and using negative return
values. This cleans up a lot of the code pathes, and with the sparse
annotations for the new sense_reason_t type allows for much better
error checking.
(nab: Convert spc_emulate_modesense + spc_emulate_modeselect to use
sense_reason_t with Roland's MODE SELECT changes)
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Now that the reservations and ALUA code have been cleaned up there is no need
for the get_device_rev method, as we only need the standards revision in the
inquiry data, where we can hardcode it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
We always support ALUA for virtual backends, and never for physical ones. Simplify
the code to just deal with these two cases and remove the superflous abstractions.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
We do not support host-level reservations for the pscsi backend, and all
virtual backends are newere than SCSI-2, so just make the combined
SPC-3 + SCSI-2 support the only supported variant and kill the switches
for the different implementations, given that this code handles the no-op
version just fine.
(hch: Update DRF_SPC2_RESERVATIONS lock usage)
Signed-off-by: Christoph Hellwig <hch@lst.de>
We can just key off ordered tag emulation of the transport_type field.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
No need to indirect through spc_parse_cdb if we only ever call it for
REPORT LUNS emulation.
(nab: Add missing EXPORT_SYMBOL for spc_emulate_report_luns)
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
These really are sbc_ops, so name them correctly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Simplify the code a lot by killing the superflous struct se_subsystem_dev.
Instead se_device is allocated early on by the backend driver, which allocates
it as part of its own per-device structure, borrowing the scheme that is for
example used for inode allocation.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch adds a new target_submit_cmd_map_sgls() to pass pre-allocated
SGL memory using transport_generic_map_mem_to_cmd() logic into the generic
target submit I/O codepath.
It also adds a target_submit_cmd() wrapper around target_submit_cmd_map_sgls()
for existing fabric code that already assumes internal target-core SGL memory
allocation.
(v2: Rename to target_submit_cmd_map_sgls + drop TARGET_SCF_MAP_MEM flag
in favor of non zero sgl_count check)
Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This patch drops se_subsystem_api->[write_cache,fua_write]_emulated flags
set by viritual FILEIO/IBLOCK/RD_MCP backend drivers in favor of explict
TRANSPORT_PLUGIN_PHBA_PDEV checks to know when to fail if userspace is
attempting to set virtual emulation bits for an pSCSI (passthrough)
backend device.
Reported-by: Christoph Hellwig <hch@lst.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Every fabric driver has to supply a se_tfo->set_fabric_sense_len()
method, just so iSCSI can return an offset of 2. However, every fabric
driver is already allocating a sense buffer and passing it into the
target core, either via transport_init_se_cmd() or target_submit_cmd().
So instead of having iSCSI pass the start of its sense buffer into the
core and then later tell the core to skip the first 2 bytes, it seems
easier for iSCSI just to do the offset of 2 when it passes the sense
buffer into the core. Then we can drop the se_tfo->set_fabric_sense_len()
everywhere, and just add a couple of lines of code to iSCSI to set the
sense data length to the beginning of the buffer right before it sends
it over the network.
(nab: Remove .set_fabric_sense_len usage from tcm_qla2xxx_npiv_ops +
change transport_get_sense_buffer to follow v3.6-rc6 code w/o
->set_fabric_sense_len usage)
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
There are no callers of se_tfo->get_fabric_sense_len(), so we should
stop having every fabric driver implement it.
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Similar to INQUIRY and MODE SENSE, construct the sense data in a
buffer and later copy it to the scatterlist. Do not do anything,
but still clear a pending unit attention condition, if the allocation
length is zero.
However, SPC tells us that "If a REQUEST SENSE command is terminated with
CHECK CONDITION status [and] the REQUEST SENSE command was received on
an I_T nexus with a pending unit attention condition (i.e., before the
device server reports CHECK CONDITION status), then the device server
shall not clear the pending unit attention condition." Do the
transport_kmap_data_sg early to detect this case.
It also tells us "Device servers shall not adjust the additional sense
length to reflect truncation if the allocation length is less than the
sense data available", so do not do that! Note that the err variable
is write-only.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
The pointer to the sense buffer is fetched by transport_get_sense_data,
but this is called by target_complete_ok_work long after pscsi_req_done
has freed the struct that contains it.
Pass instead the fabric's sense buffer to transport_complete,
and copy the data to it directly in transport_complete. Setting
SCF_TRANSPORT_TASK_SENSE also becomes a duty of transport_complete.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This was originally for helping fabrics to determine overflow/underflow
status, and has been superceeded by SCF_OVERFLOW_BIT + SCF_UNDERFLOW_BIT.
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
