On Dec 03, 2021 / 10:39, Ming Lei wrote:
> There isn't any reason to not allow zero poll queues from user
> viewpoint.
>
> Also sometimes we need to compare io poll between poll mode and irq
> mode, so not allowing poll queues is bad.
>
> Fixes: 15dfc662ef31 ("null_blk: Fix handling of submit_queues and poll_queues attributes")
> Cc: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Hi Ming,
It is good to know that the zero poll queues is useful. Having said that, I
observe zero division error [1] with your patch and the commands below. Don' we
need some more code changes to avoid the error?
# modprobe null_blk
# cd /sys/kernel/config/nullb
# mkdir test
# echo 0 > test/poll_queues
# echo 1 > test/power
Segmentation fault
[1]
[ 78.497149] divide error: 0000 [#1] PREEMPT SMP KASAN PTI
[ 78.503281] CPU: 7 PID: 1273 Comm: bash Not tainted 5.16.0-rc3+ #2
[ 78.510178] Hardware name: Supermicro X10SLL-F/X10SLL-F, BIOS 3.0 04/24/2015
[ 78.517926] RIP: 0010:blk_mq_map_queues+0x35e/0x650
[ 78.523531] Code: 72 6b 48 8b 44 24 10 41 8d 77 01 0f b6 08 48 8b 44 24 08 83 e0 07 83 c0 03 38 c8 7c 08 84 c9 0f 85 c9 02 00 00 44 89 f8 31 d2 <f7> f3 48 8b 04 24 03 50 0c 4c 89 c8 48 c1 e8 03 42 0f b6 0c 30 4c
[ 78.542990] RSP: 0018:ffff88816584fa90 EFLAGS: 00010246
[ 78.548934] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 78.556776] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff88810020a938
[ 78.564613] RBP: ffffffffafc08ab4 R08: 0000000000000000 R09: ffff88816c11ad40
[ 78.572456] R10: 0000000000000000 R11: 0000000000000001 R12: ffff88816c11ad40
[ 78.580290] R13: 0000000000000008 R14: dffffc0000000000 R15: 0000000000000000
[ 78.588124] FS: 00007f7b8110f740(0000) GS:ffff8886edb80000(0000) knlGS:0000000000000000
[ 78.596923] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 78.603380] CR2: 0000563b46186d40 CR3: 000000013ade6004 CR4: 00000000001706e0
[ 78.611224] Call Trace:
[ 78.614378] <TASK>
[ 78.617191] ? lock_is_held_type+0xe4/0x140
[ 78.622105] null_map_queues+0x247/0x400 [null_blk]
[ 78.627725] blk_mq_alloc_tag_set+0x511/0xe90
[ 78.632810] null_add_dev+0x1a88/0x20e0 [null_blk]
[ 78.638343] nullb_device_power_store+0xe4/0x240 [null_blk]
[ 78.644637] ? null_add_dev+0x20e0/0x20e0 [null_blk]
[ 78.650327] ? alloc_pages+0x13b/0x260
[ 78.654795] ? null_add_dev+0x20e0/0x20e0 [null_blk]
[ 78.660485] configfs_write_iter+0x2af/0x480
[ 78.665484] new_sync_write+0x359/0x5e0
[ 78.670040] ? new_sync_read+0x5d0/0x5d0
[ 78.674675] ? perf_instruction_pointer+0x180/0x1a0
[ 78.680265] ? lock_release+0x6d0/0x6d0
[ 78.684812] ? inode_security+0x54/0xf0
[ 78.689366] ? lock_is_held_type+0xe4/0x140
[ 78.694275] vfs_write+0x61e/0x920
[ 78.698401] ksys_write+0xe9/0x1b0
[ 78.702520] ? __ia32_sys_read+0xa0/0xa0
[ 78.707158] ? syscall_enter_from_user_mode+0x21/0x70
[ 78.712933] do_syscall_64+0x3b/0x90
[ 78.717219] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 78.722990] RIP: 0033:0x7f7b812138d7
[ 78.727280] Code: 0f 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
[ 78.746736] RSP: 002b:00007ffdad700d68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 78.755013] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f7b812138d7
[ 78.762855] RDX: 0000000000000002 RSI: 0000563b46186d40 RDI: 0000000000000001
[ 78.770690] RBP: 0000563b46186d40 R08: 0000000000000000 R09: 00007f7b812c84e0
[ 78.778524] R10: 00007f7b812c83e0 R11: 0000000000000246 R12: 0000000000000002
[ 78.786361] R13: 00007f7b8130d5a0 R14: 0000000000000002 R15: 00007f7b8130d7a0
[ 78.794215] </TASK>
[ 78.797106] Modules linked in: null_blk xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_nat_tftp nf_conntrack_tftp bridge stp llc nft_objref nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_tables ebtable_nat ebtable_broute ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 iptable_mangle iptable_raw iptable_security rfkill target_core_user target_core_mod ip_set nfnetlink ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter qrtr sunrpc intel_rapl_msr intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel iTCO_wdt intel_pmc_bxt iTCO_vendor_support at24 kvm irqbypass rapl intel_cstate joydev intel_uncore pcspkr i2c_i801 intel_pch_thermal i2c_smbus lpc_ich ses enclosure ie31200_edac video zram ip_tables crct10dif_pclmul crc32_pclmul
[ 78.797496] crc32c_intel ast drm_vram_helper drm_kms_helper ghash_clmulni_intel cec drm_ttm_helper ttm drm mpt3sas igb e1000e dca i2c_algo_bit raid_class scsi_transport_sas fuse
[ 78.899941] ---[ end trace d8088ef1fdc436e4 ]---
[ 79.005147] RIP: 0010:blk_mq_map_queues+0x35e/0x650
[ 79.010730] Code: 72 6b 48 8b 44 24 10 41 8d 77 01 0f b6 08 48 8b 44 24 08 83 e0 07 83 c0 03 38 c8 7c 08 84 c9 0f 85 c9 02 00 00 44 89 f8 31 d2 <f7> f3 48 8b 04 24 03 50 0c 4c 89 c8 48 c1 e8 03 42 0f b6 0c 30 4c
[ 79.030177] RSP: 0018:ffff88816584fa90 EFLAGS: 00010246
[ 79.036122] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 79.043974] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff88810020a938
[ 79.051825] RBP: ffffffffafc08ab4 R08: 0000000000000000 R09: ffff88816c11ad40
[ 79.059669] R10: 0000000000000000 R11: 0000000000000001 R12: ffff88816c11ad40
[ 79.067520] R13: 0000000000000008 R14: dffffc0000000000 R15: 0000000000000000
[ 79.075375] FS: 00007f7b8110f740(0000) GS:ffff8886edb80000(0000) knlGS:0000000000000000
[ 79.084170] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 79.090638] CR2: 0000563b46186d40 CR3: 000000013ade6004 CR4: 00000000001706e0
--
Best Regards,
Shin'ichiro Kawasaki
