[dm-devel] split scsi passthrough fields out of struct request V2

[Bart Van Assche]

On Wed, 2017-01-25 at 18:25 +0100, Christoph Hellwig wrote:
> Hi all,
> 
> this series splits the support for SCSI passthrough commands from the
> main struct request used all over the block layer into a separate
> scsi_request structure that drivers that want to support SCSI passthough
> need to embedded as the first thing into their request-private data,
> similar to how we handle NVMe passthrough commands.
> 
> To support this I've added support for that the private data after
> request structure to the legacy request path instead, so that it can
> be treated the same way as the blk-mq path.  Compare to the current
> scsi_cmnd allocator that actually is a major simplification.
> 
> Changes since V1:
>  - fix handling of a NULL sense pointer in __scsi_execute
>  - clean up handling of the flush flags in the block layer and MD
>  - additional small cleanup in dm-rq

Hello Christoph,

Thanks for having fixed the NULL pointer issue I had reported for v1.
However, if I try to run my srp-test testsuite on top of your
hch-block/block-pc-refactor branch (commit ID a07dc3521034) merged
with v4.10-rc5 the following appears on the console:

[  707.317403] BUG: scheduling while atomic: fio/9073/0x00000003
[  707.317404] 1 lock held by fio/9073:
[  707.317404]  #0:  (rcu_read_lock){......}, at: [<ffffffff8132618e>] __blk_mq_run_hw_queue+0xde/0x1c0
[  707.317409] Modules linked in: dm_service_time ib_srp scsi_transport_srp target_core_user uio target_core_pscsi target_core_file ib_srpt target_core_iblock target_core_mod brd netconsole xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat libcrc32c nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables af_packet ib_ipoib rdma_ucm ib_ucm ib_uverbs ib_umad rdma_cm configfs ib_cm iw_cm msr mlx4_ib ib_core sb_edac edac_core x86_pkg_temp_thermal intel_powerclamp coretemp ipmi_ssif kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul mlx4_core crc32c_intel ghash_clmulni_intel hid_generic pcbc usbhid iTCO_wdt tg3 aesni_intel
[  707.317445]  ptp iTCO_vendor_support aes_x86_64 crypto_simd pps_core glue_helper dcdbas ipmi_si ipmi_devintf libphy devlink lpc_ich cryptd pcspkr ipmi_msghandler mfd_core fjes mei_me tpm_tis button tpm_tis_core shpchp mei tpm wmi mgag200 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm sr_mod cdrom drm ehci_pci ehci_hcd usbcore usb_common sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua autofs4
[  707.317469] CPU: 6 PID: 9073 Comm: fio Tainted: G        W       4.10.0-rc5-dbg+ #1
[  707.317470] Hardware name: Dell Inc. PowerEdge R430/03XKDV, BIOS 1.0.2 11/17/2014
[  707.317470] Call Trace:
[  707.317473]  dump_stack+0x68/0x93
[  707.317475]  __schedule_bug+0x5b/0x80
[  707.317477]  __schedule+0x762/0xb00
[  707.317479]  schedule+0x38/0x90
[  707.317481]  schedule_timeout+0x2fe/0x640
[  707.317491]  io_schedule_timeout+0x9f/0x110
[  707.317493]  blk_mq_get_tag+0x158/0x260
[  707.317496]  __blk_mq_alloc_request+0x16/0xe0
[  707.317498]  blk_mq_sched_get_request+0x30d/0x360
[  707.317502]  blk_mq_alloc_request+0x3b/0x90
[  707.317505]  blk_get_request+0x2f/0x110
[  707.317507]  multipath_clone_and_map+0xcd/0x140 [dm_multipath]
[  707.317512]  map_request+0x3c/0x290 [dm_mod]
[  707.317517]  dm_mq_queue_rq+0x77/0x100 [dm_mod]
[  707.317519]  blk_mq_dispatch_rq_list+0x1ff/0x320
[  707.317521]  blk_mq_sched_dispatch_requests+0xa9/0xe0
[  707.317523]  __blk_mq_run_hw_queue+0x122/0x1c0
[  707.317528]  blk_mq_run_hw_queue+0x84/0x90
[  707.317530]  blk_mq_flush_plug_list+0x39f/0x480
[  707.317531]  blk_flush_plug_list+0xee/0x270
[  707.317533]  blk_finish_plug+0x27/0x40
[  707.317534]  do_io_submit+0x475/0x900
[  707.317537]  SyS_io_submit+0xb/0x10
[  707.317539]  entry_SYSCALL_64_fastpath+0x18/0xad

Bart.