From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- fs/fuse/req.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 99 insertions(+) create mode 100644 fs/fuse/req.c (limited to 'fs/fuse/req.c') diff --git a/fs/fuse/req.c b/fs/fuse/req.c new file mode 100644 index 000000000..a01ee743d --- /dev/null +++ b/fs/fuse/req.c @@ -0,0 +1,99 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include "dev.h" +#include "fuse_i.h" + +static int fuse_fill_creds(struct fuse_mount *fm, struct fuse_args *args, struct mnt_idmap *idmap) +{ + struct fuse_conn *fc = fm->fc; + bool no_idmap = !fm->sb || (fm->sb->s_iflags & SB_I_NOIDMAP); + kuid_t fsuid = mapped_fsuid(idmap, fc->user_ns); + kgid_t fsgid = mapped_fsgid(idmap, fc->user_ns); + + args->pid = pid_nr_ns(task_pid(current), fc->pid_ns); + + if (args->force) { + if (args->nocreds) + return 0; + + if (no_idmap) { + args->uid = from_kuid_munged(fc->user_ns, current_fsuid()); + args->gid = from_kgid_munged(fc->user_ns, current_fsgid()); + } else { + args->uid = FUSE_INVALID_UIDGID; + args->gid = FUSE_INVALID_UIDGID; + } + return 0; + } + + WARN_ON(args->nocreds); + /* + * Keep the old behavior when idmappings support was not + * declared by a FUSE server. + * + * For those FUSE servers who support idmapped mounts, we send UID/GID + * only along with "inode creation" fuse requests, otherwise idmap == + * &invalid_mnt_idmap and req->in.h.{u,g}id will be equal to + * FUSE_INVALID_UIDGID. + */ + if (no_idmap) { + fsuid = current_fsuid(); + fsgid = current_fsgid(); + } + args->uid = from_kuid(fc->user_ns, fsuid); + args->gid = from_kgid(fc->user_ns, fsgid); + + if (no_idmap && unlikely(args->uid == ((uid_t)-1) || args->gid == ((gid_t)-1))) + return -EOVERFLOW; + + return 0; +} + +static int fuse_req_prep(struct fuse_mount *fm, struct fuse_args *args, struct mnt_idmap *idmap) +{ + if (!args->force && fm->fc->conn_error) + return -ECONNREFUSED; + + return fuse_fill_creds(fm, args, idmap); +} + +ssize_t __fuse_simple_request(struct mnt_idmap *idmap, struct fuse_mount *fm, + struct fuse_args *args) +{ + struct fuse_conn *fc = fm->fc; + int err = fuse_req_prep(fm, args, idmap); + + if (err) + return err; + + return fuse_chan_send(fc->chan, args); +} + +int fuse_simple_background(struct fuse_mount *fm, struct fuse_args *args, gfp_t gfp_flags) +{ + struct fuse_conn *fc = fm->fc; + int err; + + WARN_ON(args->force && !args->nocreds); + + err = fuse_req_prep(fm, args, &invalid_mnt_idmap); + if (err) + return err; + + return fuse_chan_send_bg(fc->chan, args, gfp_flags); +} +EXPORT_SYMBOL_GPL(fuse_simple_background); + +int fuse_simple_notify_reply(struct fuse_mount *fm, struct fuse_args *args, u64 unique) +{ + struct fuse_conn *fc = fm->fc; + int err; + + WARN_ON(args->force && !args->nocreds); + + err = fuse_req_prep(fm, args, &invalid_mnt_idmap); + if (err) + return err; + + return fuse_chan_send_notify_reply(fc->chan, args, unique); +} -- cgit v1.3.1