From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- io_uring/fs.c | 306 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 306 insertions(+) create mode 100644 io_uring/fs.c (limited to 'io_uring/fs.c') diff --git a/io_uring/fs.c b/io_uring/fs.c new file mode 100644 index 000000000..26ea841a2 --- /dev/null +++ b/io_uring/fs.c @@ -0,0 +1,306 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "../fs/internal.h" + +#include "io_uring.h" +#include "fs.h" + +struct io_rename { + struct file *file; + int old_dfd; + int new_dfd; + struct delayed_filename oldpath; + struct delayed_filename newpath; + int flags; +}; + +struct io_unlink { + struct file *file; + int dfd; + int flags; + struct delayed_filename filename; +}; + +struct io_mkdir { + struct file *file; + int dfd; + umode_t mode; + struct delayed_filename filename; +}; + +struct io_link { + struct file *file; + int old_dfd; + int new_dfd; + struct delayed_filename oldpath; + struct delayed_filename newpath; + int flags; +}; + +int io_renameat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename); + const char __user *oldf, *newf; + int err; + + if (sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + if (unlikely(req->flags & REQ_F_FIXED_FILE)) + return -EBADF; + + ren->old_dfd = READ_ONCE(sqe->fd); + oldf = u64_to_user_ptr(READ_ONCE(sqe->addr)); + newf = u64_to_user_ptr(READ_ONCE(sqe->addr2)); + ren->new_dfd = READ_ONCE(sqe->len); + ren->flags = READ_ONCE(sqe->rename_flags); + + err = delayed_getname(&ren->oldpath, oldf); + if (unlikely(err)) + return err; + + err = delayed_getname(&ren->newpath, newf); + if (unlikely(err)) { + dismiss_delayed_filename(&ren->oldpath); + return err; + } + + req->flags |= REQ_F_NEED_CLEANUP; + req->flags |= REQ_F_FORCE_ASYNC; + return 0; +} + +int io_renameat(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename); + CLASS(filename_complete_delayed, old)(&ren->oldpath); + CLASS(filename_complete_delayed, new)(&ren->newpath); + int ret; + + WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK); + + ret = filename_renameat2(ren->old_dfd, old, + ren->new_dfd, new, ren->flags); + + req->flags &= ~REQ_F_NEED_CLEANUP; + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} + +void io_renameat_cleanup(struct io_kiocb *req) +{ + struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename); + + dismiss_delayed_filename(&ren->oldpath); + dismiss_delayed_filename(&ren->newpath); +} + +int io_unlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_unlink *un = io_kiocb_to_cmd(req, struct io_unlink); + const char __user *fname; + int err; + + if (sqe->off || sqe->len || sqe->buf_index || sqe->splice_fd_in || + sqe->addr3 || sqe->__pad2[0]) + return -EINVAL; + if (unlikely(req->flags & REQ_F_FIXED_FILE)) + return -EBADF; + + un->dfd = READ_ONCE(sqe->fd); + + un->flags = READ_ONCE(sqe->unlink_flags); + if (un->flags & ~AT_REMOVEDIR) + return -EINVAL; + + fname = u64_to_user_ptr(READ_ONCE(sqe->addr)); + err = delayed_getname(&un->filename, fname); + if (unlikely(err)) + return err; + + req->flags |= REQ_F_NEED_CLEANUP; + req->flags |= REQ_F_FORCE_ASYNC; + return 0; +} + +int io_unlinkat(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_unlink *un = io_kiocb_to_cmd(req, struct io_unlink); + CLASS(filename_complete_delayed, name)(&un->filename); + int ret; + + WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK); + + if (un->flags & AT_REMOVEDIR) + ret = filename_rmdir(un->dfd, name); + else + ret = filename_unlinkat(un->dfd, name); + + req->flags &= ~REQ_F_NEED_CLEANUP; + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} + +void io_unlinkat_cleanup(struct io_kiocb *req) +{ + struct io_unlink *ul = io_kiocb_to_cmd(req, struct io_unlink); + + dismiss_delayed_filename(&ul->filename); +} + +int io_mkdirat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_mkdir *mkd = io_kiocb_to_cmd(req, struct io_mkdir); + const char __user *fname; + int err; + + if (sqe->off || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + if (unlikely(req->flags & REQ_F_FIXED_FILE)) + return -EBADF; + + mkd->dfd = READ_ONCE(sqe->fd); + mkd->mode = READ_ONCE(sqe->len); + + fname = u64_to_user_ptr(READ_ONCE(sqe->addr)); + err = delayed_getname(&mkd->filename, fname); + if (unlikely(err)) + return err; + + req->flags |= REQ_F_NEED_CLEANUP; + req->flags |= REQ_F_FORCE_ASYNC; + return 0; +} + +int io_mkdirat(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_mkdir *mkd = io_kiocb_to_cmd(req, struct io_mkdir); + CLASS(filename_complete_delayed, name)(&mkd->filename); + int ret; + + WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK); + + ret = filename_mkdirat(mkd->dfd, name, mkd->mode); + + req->flags &= ~REQ_F_NEED_CLEANUP; + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} + +void io_mkdirat_cleanup(struct io_kiocb *req) +{ + struct io_mkdir *md = io_kiocb_to_cmd(req, struct io_mkdir); + + dismiss_delayed_filename(&md->filename); +} + +int io_symlinkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_link *sl = io_kiocb_to_cmd(req, struct io_link); + const char __user *oldpath, *newpath; + int err; + + if (sqe->len || sqe->rw_flags || sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + if (unlikely(req->flags & REQ_F_FIXED_FILE)) + return -EBADF; + + sl->new_dfd = READ_ONCE(sqe->fd); + oldpath = u64_to_user_ptr(READ_ONCE(sqe->addr)); + newpath = u64_to_user_ptr(READ_ONCE(sqe->addr2)); + + err = delayed_getname(&sl->oldpath, oldpath); + if (unlikely(err)) + return err; + + err = delayed_getname(&sl->newpath, newpath); + if (unlikely(err)) { + dismiss_delayed_filename(&sl->oldpath); + return err; + } + + req->flags |= REQ_F_NEED_CLEANUP; + req->flags |= REQ_F_FORCE_ASYNC; + return 0; +} + +int io_symlinkat(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_link *sl = io_kiocb_to_cmd(req, struct io_link); + CLASS(filename_complete_delayed, old)(&sl->oldpath); + CLASS(filename_complete_delayed, new)(&sl->newpath); + int ret; + + WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK); + + ret = filename_symlinkat(old, sl->new_dfd, new); + + req->flags &= ~REQ_F_NEED_CLEANUP; + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} + +int io_linkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + struct io_link *lnk = io_kiocb_to_cmd(req, struct io_link); + const char __user *oldf, *newf; + int err; + + if (sqe->buf_index || sqe->splice_fd_in) + return -EINVAL; + if (unlikely(req->flags & REQ_F_FIXED_FILE)) + return -EBADF; + + lnk->old_dfd = READ_ONCE(sqe->fd); + lnk->new_dfd = READ_ONCE(sqe->len); + oldf = u64_to_user_ptr(READ_ONCE(sqe->addr)); + newf = u64_to_user_ptr(READ_ONCE(sqe->addr2)); + lnk->flags = READ_ONCE(sqe->hardlink_flags); + + err = delayed_getname_uflags(&lnk->oldpath, oldf, lnk->flags); + if (unlikely(err)) + return err; + + err = delayed_getname(&lnk->newpath, newf); + if (unlikely(err)) { + dismiss_delayed_filename(&lnk->oldpath); + return err; + } + + req->flags |= REQ_F_NEED_CLEANUP; + req->flags |= REQ_F_FORCE_ASYNC; + return 0; +} + +int io_linkat(struct io_kiocb *req, unsigned int issue_flags) +{ + struct io_link *lnk = io_kiocb_to_cmd(req, struct io_link); + CLASS(filename_complete_delayed, old)(&lnk->oldpath); + CLASS(filename_complete_delayed, new)(&lnk->newpath); + int ret; + + WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK); + + ret = filename_linkat(lnk->old_dfd, old, lnk->new_dfd, new, lnk->flags); + + req->flags &= ~REQ_F_NEED_CLEANUP; + io_req_set_res(req, ret, 0); + return IOU_COMPLETE; +} + +void io_link_cleanup(struct io_kiocb *req) +{ + struct io_link *sl = io_kiocb_to_cmd(req, struct io_link); + + dismiss_delayed_filename(&sl->oldpath); + dismiss_delayed_filename(&sl->newpath); +} -- cgit v1.3.1