kernel/linux.git/io_uring/sqpoll.c, branch v6.19.11

Merge branch 'io_uring-6.18' into for-6.19/io_uring

2025-11-13T14:26:37+00:00

Merge 6.18-rc io_uring fixes, as certain coming changes depend on some of these. * io_uring-6.18: io_uring/rsrc: don't use blk_rq_nr_phys_segments() as number of bvecs io_uring/query: return number of available queries io_uring/rw: ensure allocated iovec gets cleared for early failure io_uring: fix regbuf vector size truncation io_uring: fix types for region size calulation io_uring/zcrx: remove sync refill uapi io_uring: fix buffer auto-commit for multishot uring_cmd io_uring: correct __must_hold annotation in io_install_fixed_file io_uring zcrx: add MAINTAINERS entry io_uring: Fix code indentation error io_uring/sqpoll: be smarter on when to update the stime usage io_uring/sqpoll: switch away from getrusage() for CPU accounting io_uring: fix incorrect unlikely() usage in io_waitid_prep() Signed-off-by: Jens Axboe

io_uring/cancel: move cancelation code from io_uring.c to cancel.c

2025-11-04T16:32:09+00:00

There's a bunch of code strictly dealing with cancelations, and that code really belongs in cancel.c rather than in the core io_uring.c file. Move the code there. Mostly mechanical, only real oddity here is that struct io_defer_entry now needs to be visible across both io_uring.c and cancel.c. Signed-off-by: Jens Axboe

io_uring/sqpoll: be smarter on when to update the stime usage

2025-10-22T16:55:33+00:00

The current approach is a bit naive, and hence calls the time querying way too often. Only start the "doing work" timer when there's actual work to do, and then use that information to terminate (and account) the work time once done. This greatly reduces the frequency of these calls, when they cannot have changed anyway. Running a basic random reader that is setup to use SQPOLL, a profile before this change shows these as the top cycle consumers: + 32.60% iou-sqp-1074 [kernel.kallsyms] [k] thread_group_cputime_adjusted + 19.97% iou-sqp-1074 [kernel.kallsyms] [k] thread_group_cputime + 12.20% io_uring io_uring [.] submitter_uring_fn + 4.13% iou-sqp-1074 [kernel.kallsyms] [k] getrusage + 2.45% iou-sqp-1074 [kernel.kallsyms] [k] io_submit_sqes + 2.18% iou-sqp-1074 [kernel.kallsyms] [k] __pi_memset_generic + 2.09% iou-sqp-1074 [kernel.kallsyms] [k] cputime_adjust and after this change, top of profile looks as follows: + 36.23% io_uring io_uring [.] submitter_uring_fn + 23.26% iou-sqp-819 [kernel.kallsyms] [k] io_sq_thread + 10.14% iou-sqp-819 [kernel.kallsyms] [k] io_sq_tw + 6.52% iou-sqp-819 [kernel.kallsyms] [k] tctx_task_work_run + 4.82% iou-sqp-819 [kernel.kallsyms] [k] nvme_submit_cmds.part.0 + 2.91% iou-sqp-819 [kernel.kallsyms] [k] io_submit_sqes [...] 0.02% iou-sqp-819 [kernel.kallsyms] [k] cputime_adjust where it's spending the cycles on things that actually matter. Reported-by: Fengnan Chang Cc: stable@vger.kernel.org Fixes: 3fcb9d17206e ("io_uring/sqpoll: statistics of the true utilization of sq threads") Signed-off-by: Jens Axboe

io_uring/sqpoll: switch away from getrusage() for CPU accounting

2025-10-22T16:51:20+00:00

getrusage() does a lot more than what the SQPOLL accounting needs, the latter only cares about (and uses) the stime. Rather than do a full RUSAGE_SELF summation, just query the used stime instead. Cc: stable@vger.kernel.org Fixes: 3fcb9d17206e ("io_uring/sqpoll: statistics of the true utilization of sq threads") Reviewed-by: Gabriel Krisman Bertazi Signed-off-by: Jens Axboe

io_uring/sqpoll: don't put task_struct on tctx setup failure

2025-06-17T12:43:18+00:00

A recent commit moved the error handling of sqpoll thread and tctx failures into the thread itself, as part of fixing an issue. However, it missed that tctx allocation may also fail, and that io_sq_offload_create() does its own error handling for the task_struct in that case. Remove the manual task putting in io_sq_offload_create(), as io_sq_thread() will notice that the tctx did not get setup and hence it should put itself and exit. Reported-by: syzbot+763e12bbf004fb1062e4@syzkaller.appspotmail.com Fixes: ac0b8b327a56 ("io_uring: fix use-after-free of sq->thread in __io_uring_show_fdinfo()") Signed-off-by: Jens Axboe

io_uring: remove duplicate io_uring_alloc_task_context() definition

2025-06-17T12:41:48+00:00

This function exists in both tctx.h (where it belongs) and in io_uring.h as a remnant of before the tctx handling code got split out. Remove the io_uring.h definition and ensure that sqpoll.c includes the tctx.h header to get the definition. Signed-off-by: Jens Axboe

io_uring: consistently use rcu semantics with sqpoll thread

2025-06-12T14:17:09+00:00

The sqpoll thread is dereferenced with rcu read protection in one place, so it needs to be annotated as an __rcu type, and should consistently use rcu helpers for access and assignment to make sparse happy. Since most of the accesses occur under the sqd->lock, we can use rcu_dereference_protected() without declaring an rcu read section. Provide a simple helper to get the thread from a locked context. Fixes: ac0b8b327a5677d ("io_uring: fix use-after-free of sq->thread in __io_uring_show_fdinfo()") Signed-off-by: Keith Busch Link: https://lore.kernel.org/r/20250611205343.1821117-1-kbusch@meta.com [axboe: fold in fix for register.c] Signed-off-by: Jens Axboe

io_uring: fix use-after-free of sq->thread in __io_uring_show_fdinfo()

2025-06-10T17:20:04+00:00

syzbot reports: BUG: KASAN: slab-use-after-free in getrusage+0x1109/0x1a60 Read of size 8 at addr ffff88810de2d2c8 by task a.out/304 CPU: 0 UID: 0 PID: 304 Comm: a.out Not tainted 6.16.0-rc1 #1 PREEMPT(voluntary) Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: dump_stack_lvl+0x53/0x70 print_report+0xd0/0x670 ? __pfx__raw_spin_lock_irqsave+0x10/0x10 ? getrusage+0x1109/0x1a60 kasan_report+0xce/0x100 ? getrusage+0x1109/0x1a60 getrusage+0x1109/0x1a60 ? __pfx_getrusage+0x10/0x10 __io_uring_show_fdinfo+0x9fe/0x1790 ? ksys_read+0xf7/0x1c0 ? do_syscall_64+0xa4/0x260 ? vsnprintf+0x591/0x1100 ? __pfx___io_uring_show_fdinfo+0x10/0x10 ? __pfx_vsnprintf+0x10/0x10 ? mutex_trylock+0xcf/0x130 ? __pfx_mutex_trylock+0x10/0x10 ? __pfx_show_fd_locks+0x10/0x10 ? io_uring_show_fdinfo+0x57/0x80 io_uring_show_fdinfo+0x57/0x80 seq_show+0x38c/0x690 seq_read_iter+0x3f7/0x1180 ? inode_set_ctime_current+0x160/0x4b0 seq_read+0x271/0x3e0 ? __pfx_seq_read+0x10/0x10 ? __pfx__raw_spin_lock+0x10/0x10 ? __mark_inode_dirty+0x402/0x810 ? selinux_file_permission+0x368/0x500 ? file_update_time+0x10f/0x160 vfs_read+0x177/0xa40 ? __pfx___handle_mm_fault+0x10/0x10 ? __pfx_vfs_read+0x10/0x10 ? mutex_lock+0x81/0xe0 ? __pfx_mutex_lock+0x10/0x10 ? fdget_pos+0x24d/0x4b0 ksys_read+0xf7/0x1c0 ? __pfx_ksys_read+0x10/0x10 ? do_user_addr_fault+0x43b/0x9c0 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f0f74170fc9 Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 8 RSP: 002b:00007fffece049e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0f74170fc9 RDX: 0000000000001000 RSI: 00007fffece049f0 RDI: 0000000000000004 RBP: 00007fffece05ad0 R08: 0000000000000000 R09: 00007fffece04d90 R10: 0000000000000000 R11: 0000000000000206 R12: 00005651720a1100 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 298: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_slab_alloc+0x6e/0x70 kmem_cache_alloc_node_noprof+0xe8/0x330 copy_process+0x376/0x5e00 create_io_thread+0xab/0xf0 io_sq_offload_create+0x9ed/0xf20 io_uring_setup+0x12b0/0x1cc0 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 22: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x37/0x50 kmem_cache_free+0xc4/0x360 rcu_core+0x5ff/0x19f0 handle_softirqs+0x18c/0x530 run_ksoftirqd+0x20/0x30 smpboot_thread_fn+0x287/0x6c0 kthread+0x30d/0x630 ret_from_fork+0xef/0x1a0 ret_from_fork_asm+0x1a/0x30 Last potentially related work creation: kasan_save_stack+0x33/0x60 kasan_record_aux_stack+0x8c/0xa0 __call_rcu_common.constprop.0+0x68/0x940 __schedule+0xff2/0x2930 __cond_resched+0x4c/0x80 mutex_lock+0x5c/0xe0 io_uring_del_tctx_node+0xe1/0x2b0 io_uring_clean_tctx+0xb7/0x160 io_uring_cancel_generic+0x34e/0x760 do_exit+0x240/0x2350 do_group_exit+0xab/0x220 __x64_sys_exit_group+0x39/0x40 x64_sys_call+0x1243/0x1840 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88810de2cb00 which belongs to the cache task_struct of size 3712 The buggy address is located 1992 bytes inside of freed 3712-byte region [ffff88810de2cb00, ffff88810de2d980) which is caused by the task_struct pointed to by sq->thread being released while it is being used in the function __io_uring_show_fdinfo(). Holding ctx->uring_lock does not prevent ehre relase or exit of sq->thread. Fix this by assigning and looking up ->thread under RCU, and grabbing a reference to the task_struct. This ensures that it cannot get released while fdinfo is using it. Reported-by: syzbot+531502bbbe51d2f769f4@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/682b06a5.a70a0220.3849cf.00b3.GAE@google.com Fixes: 3fcb9d17206e ("io_uring/sqpoll: statistics of the true utilization of sq threads") Signed-off-by: Penglei Jiang Link: https://lore.kernel.org/r/20250610171801.70960-1-superman.xpt@gmail.com [axboe: massage commit message] Signed-off-by: Jens Axboe

io_uring/sqpoll: Increase task_work submission batch size

2025-05-09T13:56:53+00:00

Our QA team reported a 10%-23%, throughput reduction on an io_uring sqpoll testcase doing IO to a null_blk, that I traced back to a reduction of the device submission queue depth utilization. It turns out that, after commit af5d68f8892f ("io_uring/sqpoll: manage task_work privately"), we capped the number of task_work entries that can be completed from a single spin of sqpoll to only 8 entries, before the sqpoll goes around to (potentially) sleep. While this cap doesn't drive the submission side directly, it impacts the completion behavior, which affects the number of IO queued by fio per sqpoll cycle on the submission side, and io_uring ends up seeing less ios per sqpoll cycle. As a result, block layer plugging is less effective, and we see more time spent inside the block layer in profilings charts, and increased submission latency measured by fio. There are other places that have increased overhead once sqpoll sleeps more often, such as the sqpoll utilization calculation. But, in this microbenchmark, those were not representative enough in perf charts, and their removal didn't yield measurable changes in throughput. The major overhead comes from the fact we plug less, and less often, when submitting to the block layer. My benchmark is: fio --ioengine=io_uring --direct=1 --iodepth=128 --runtime=300 --bs=4k \ --invalidate=1 --time_based --ramp_time=10 --group_reporting=1 \ --filename=/dev/nullb0 --name=RandomReads-direct-nullb-sqpoll-4k-1 \ --rw=randread --numjobs=1 --sqthread_poll In one machine, tested on top of Linux 6.15-rc1, we have the following baseline: READ: bw=4994MiB/s (5236MB/s), 4994MiB/s-4994MiB/s (5236MB/s-5236MB/s), io=439GiB (471GB), run=90001-90001msec With this patch: READ: bw=5762MiB/s (6042MB/s), 5762MiB/s-5762MiB/s (6042MB/s-6042MB/s), io=506GiB (544GB), run=90001-90001msec which is a 15% improvement in measured bandwidth. The average submission latency is noticeably lowered too. As measured by fio: Baseline: lat (usec): min=20, max=241, avg=99.81, stdev=3.38 Patched: lat (usec): min=26, max=226, avg=86.48, stdev=4.82 If we look at blktrace, we can also see the plugging behavior is improved. In the baseline, we end up limited to plugging 8 requests in the block layer regardless of the device queue depth size, while after patching we can drive more io, and we manage to utilize the full device queue. In the baseline, after a stabilization phase, an ordinary submission looks like: 254,0 1 49942 0.016028795 5977 U N [iou-sqp-5976] 7 After patching, I see consistently more requests per unplug. 254,0 1 4996 0.001432872 3145 U N [iou-sqp-3144] 32 Ideally, the cap size would at least be the deep enough to fill the device queue, but we can't predict that behavior, or assume all IO goes to a single device, and thus can't guess the ideal batch size. We also don't want to let the tw run unbounded, though I'm not sure it would really be a problem. Instead, let's just give it a more sensible value that will allow for more efficient batching. I've tested with different cap values, and initially proposed to increase the cap to 1024. Jens argued it is too big of a bump and I observed that, with 32, I'm no longer able to observe this bottleneck in any of my machines. Fixes: af5d68f8892f ("io_uring/sqpoll: manage task_work privately") Signed-off-by: Gabriel Krisman Bertazi Link: https://lore.kernel.org/r/20250508181203.3785544-1-krisman@suse.de Signed-off-by: Jens Axboe

Merge tag 'execve-v6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

2025-01-20T21:27:58+00:00

Pull execve updates from Kees Cook: - fix up /proc/pid/comm in the execveat(AT_EMPTY_PATH) case (Tycho Andersen, Kees Cook) - binfmt_misc: Fix comment typos (Christophe JAILLET) - move empty argv[0] warning closer to actual logic (Nir Lichtman) - remove legacy custom binfmt modules autoloading (Nir Lichtman) - Make sure set_task_comm() always NUL-terminates - binfmt_flat: Fix integer overflow bug on 32 bit systems (Dan Carpenter) - coredump: Do not lock when copying "comm" - MAINTAINERS: add auxvec.h and set myself as maintainer * tag 'execve-v6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: binfmt_flat: Fix integer overflow bug on 32 bit systems selftests/exec: add a test for execveat()'s comm exec: fix up /proc/pid/comm in the execveat(AT_EMPTY_PATH) case exec: Make sure task->comm is always NUL-terminated exec: remove legacy custom binfmt modules autoloading exec: move warning of null argv to be next to the relevant code fs: binfmt: Fix a typo MAINTAINERS: exec: Mark Kees as maintainer MAINTAINERS: exec: Add auxvec.h UAPI coredump: Do not lock during 'comm' reporting