kernel/linux.git/drivers/target/loopback, branch v6.19.12

scsi: target: tcm_loop: Drain commands in target_reset handler

2026-04-11T12:29:19+00:00

[ Upstream commit 1333eee56cdf3f0cf67c6ab4114c2c9e0a952026 ] tcm_loop_target_reset() violates the SCSI EH contract: it returns SUCCESS without draining any in-flight commands. The SCSI EH documentation (scsi_eh.rst) requires that when a reset handler returns SUCCESS the driver has made lower layers "forget about timed out scmds" and is ready for new commands. Every other SCSI LLD (virtio_scsi, mpt3sas, ipr, scsi_debug, mpi3mr) enforces this by draining or completing outstanding commands before returning SUCCESS. Because tcm_loop_target_reset() doesn't drain, the SCSI EH reuses in-flight scsi_cmnd structures for recovery commands (e.g. TUR) while the target core still has async completion work queued for the old se_cmd. The memset in queuecommand zeroes se_lun and lun_ref_active, causing transport_lun_remove_cmd() to skip its percpu_ref_put(). The leaked LUN reference prevents transport_clear_lun_ref() from completing, hanging configfs LUN unlink forever in D-state: INFO: task rm:264 blocked for more than 122 seconds. rm D 0 264 258 0x00004000 Call Trace: __schedule+0x3d0/0x8e0 schedule+0x36/0xf0 transport_clear_lun_ref+0x78/0x90 [target_core_mod] core_tpg_remove_lun+0x28/0xb0 [target_core_mod] target_fabric_port_unlink+0x50/0x60 [target_core_mod] configfs_unlink+0x156/0x1f0 [configfs] vfs_unlink+0x109/0x290 do_unlinkat+0x1d5/0x2d0 Fix this by making tcm_loop_target_reset() actually drain commands: 1. Issue TMR_LUN_RESET via tcm_loop_issue_tmr() to drain all commands that the target core knows about (those not yet CMD_T_COMPLETE). 2. Use blk_mq_tagset_busy_iter() to iterate all started requests and flush_work() on each se_cmd — this drains any deferred completion work for commands that already had CMD_T_COMPLETE set before the TMR (which the TMR skips via __target_check_io_state()). This is the same pattern used by mpi3mr, scsi_debug, and libsas to drain outstanding commands during reset. Fixes: e0eb5d38b732 ("scsi: target: tcm_loop: Use block cmd allocator for se_cmds") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Josef Bacik Link: https://patch.msgid.link/27011aa34c8f6b1b94d2e3cf5655b6d037f53428.1773706803.git.josef@toxicpanda.com Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

scsi: target: tcm_loop: Fix segfault in tcm_loop_tpg_address_show()

2025-11-08T17:30:02+00:00

If the allocation of tl_hba->sh fails in tcm_loop_driver_probe() and we attempt to dereference it in tcm_loop_tpg_address_show() we will get a segfault, see below for an example. So, check tl_hba->sh before dereferencing it. Unable to allocate struct scsi_host BUG: kernel NULL pointer dereference, address: 0000000000000194 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 PID: 8356 Comm: tokio-runtime-w Not tainted 6.6.104.2-4.azl3 #1 Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 09/28/2024 RIP: 0010:tcm_loop_tpg_address_show+0x2e/0x50 [tcm_loop] ... Call Trace: configfs_read_iter+0x12d/0x1d0 [configfs] vfs_read+0x1b5/0x300 ksys_read+0x6f/0xf0 ... Cc: stable@vger.kernel.org Fixes: 2628b352c3d4 ("tcm_loop: Show address of tpg in configfs") Signed-off-by: Hamza Mahfooz Reviewed-by: Chaitanya Kulkarni Reviewed-by: Allen Pais Link: https://patch.msgid.link/1762370746-6304-1-git-send-email-hamzamahfooz@linux.microsoft.com Signed-off-by: Martin K. Petersen

scsi: target: tcm_loop: Fix wrong abort tag

2025-03-18T02:04:21+00:00

When the tcm_loop_nr_hw_queues is set to a value greater than 1, the tags of requests in the block layer are no longer unique. This may lead to erroneous aborting of commands with the same tag. The issue can be resolved by using blk_mq_unique_tag to generate globally unique identifiers by combining the hardware queue index and per-queue tags. Fixes: 6375f8908255 ("tcm_loop: Fixup tag handling") Signed-off-by: Guixin Liu Link: https://lore.kernel.org/r/20250313014728.105849-1-kanie@linux.alibaba.com Signed-off-by: Martin K. Petersen

scsi: target: tcm_loop: Make tcm_loop_lld_bus const

2024-02-06T01:58:55+00:00

Now that the driver core can properly handle constant struct bus_type, move the tcm_loop_lld_bus variable to be a constant structure as well, placing it into read-only memory which can not be modified at runtime. Cc: Greg Kroah-Hartman Suggested-by: Greg Kroah-Hartman Signed-off-by: Ricardo B. Marliere Link: https://lore.kernel.org/r/20240204-bus_cleanup-target-v1-1-96106936c4ab@marliere.net Reviewed-by: Greg Kroah-Hartman Signed-off-by: Martin K. Petersen

scsi: target: Allow userspace to request direct submissions

2023-10-13T19:53:58+00:00

This allows userspace to request the fabric drivers do direct submissions if they support it. With the new device file, submit_type, users can write 0 - 2 to control how commands are submitted to the backend: 0 - TARGET_FABRIC_DEFAULT_SUBMIT - LIO will use the fabric's default submission type. This is the default for compat. 1 - TARGET_DIRECT_SUBMIT - LIO will submit the cmd to the backend from the calling context if the fabric the cmd was received on supports it, else it will use the fabric's default type. 2 - TARGET_QUEUE_SUBMIT - LIO will queue the cmd to the LIO submission workqueue which will pass it to the backend. When using an NVMe drive and vhost-scsi with direct submission we see around a 20% improvement in 4K I/Os: fio jobs 1 2 4 8 10 -------------------------------------------------- defer 94K 190K 394K 770K 890K direct 128K 252K 488K 950K - And when using the queueing mode, we now no longer see issues like where the iSCSI tx thread is blocked in the block layer waiting on a tag so it can't respond to a nop or perform I/Os for other LUs. Signed-off-by: Mike Christie Link: https://lore.kernel.org/r/20230928020907.5730-6-michael.christie@oracle.com Signed-off-by: Martin K. Petersen

scsi: target: Have drivers report if they support direct submissions

2023-10-13T19:53:57+00:00

In some cases, like with multiple LUN targets or where the target has to respond to transport level requests from the receiving context it can be better to defer cmd submission to a helper thread. If the backend driver blocks on something like request/tag allocation it can block the entire target submission path and other LUs and transport IO on that session. In other cases like single LUN targets with storage that can support all the commands that the target can queue, then it's best to submit the cmd to the backend from the target's cmd receiving context. Subsequent commits will allow the user to config what they prefer, but drivers like loop can't directly submit because they can be called from a context that can't sleep. And, drivers like vhost-scsi can support direct submission, but need to keep their default behavior of deferring execution to avoid possible regressions where the backend can block. Make the drivers tell LIO core if they support direct submissions and their current default, so we can prevent users from misconfiguring the system and initialize devices correctly. Signed-off-by: Mike Christie Link: https://lore.kernel.org/r/20230928020907.5730-2-michael.christie@oracle.com Signed-off-by: Martin K. Petersen

scsi: target: tcm_loop: Remove redundant driver match function

2023-03-25T00:44:14+00:00

If there is no driver match function, the driver core assumes that each candidate pair (driver, device) matches. See driver_match_device(). pseudo_lld_bus_match() always returns 1 and is therefore equivalent to not registering a match function. Remove it. Signed-off-by: Lizhe Link: https://lore.kernel.org/r/20230319043518.297490-1-sensor1010@163.com Signed-off-by: Martin K. Petersen

Merge patch series "Constify most SCSI host templates"

2023-03-25T00:13:03+00:00

Bart Van Assche says: It helps humans and the compiler if it is made explicit that SCSI host templates are not modified. Hence this patch series that constifies most SCSI host templates. Please consider this patch series for the next merge window. Link: https://lore.kernel.org/r/20230322195515.1267197-1-bvanassche@acm.org Signed-off-by: Martin K. Petersen

scsi: target: tcm-loop: Declare SCSI host template const

2023-03-24T23:20:00+00:00

Make it explicit that the SCSI host template is not modified. Signed-off-by: Bart Van Assche Link: https://lore.kernel.org/r/20230322195515.1267197-79-bvanassche@acm.org Signed-off-by: Martin K. Petersen

scsi: target: loop: Remove default fabric ops callouts

2023-03-17T03:36:36+00:00

Remove callouts that are identical to the default implementations in TCM Core. Signed-off-by: Dmitry Bogdanov Link: https://lore.kernel.org/r/20230313181110.20566-5-d.bogdanov@yadro.com Signed-off-by: Martin K. Petersen