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 --- init/do_mounts.c | 520 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 520 insertions(+) create mode 100644 init/do_mounts.c (limited to 'init/do_mounts.c') diff --git a/init/do_mounts.c b/init/do_mounts.c new file mode 100644 index 000000000..95e0b3a0f --- /dev/null +++ b/init/do_mounts.c @@ -0,0 +1,520 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +#include "do_mounts.h" + +int root_mountflags = MS_RDONLY | MS_SILENT; +static char __initdata saved_root_name[64]; +static int root_wait; + +dev_t ROOT_DEV; + +static int __init readonly(char *str) +{ + if (*str) + return 0; + root_mountflags |= MS_RDONLY; + return 1; +} + +static int __init readwrite(char *str) +{ + if (*str) + return 0; + root_mountflags &= ~MS_RDONLY; + return 1; +} + +__setup("ro", readonly); +__setup("rw", readwrite); + +static int __init root_dev_setup(char *line) +{ + strscpy(saved_root_name, line, sizeof(saved_root_name)); + return 1; +} + +__setup("root=", root_dev_setup); + +static int __init rootwait_setup(char *str) +{ + if (*str) + return 0; + root_wait = -1; + return 1; +} + +__setup("rootwait", rootwait_setup); + +static int __init rootwait_timeout_setup(char *str) +{ + int sec; + + if (kstrtoint(str, 0, &sec) || sec < 0) { + pr_warn("ignoring invalid rootwait value\n"); + goto ignore; + } + + if (check_mul_overflow(sec, MSEC_PER_SEC, &root_wait)) { + pr_warn("ignoring excessive rootwait value\n"); + goto ignore; + } + + return 1; + +ignore: + /* Fallback to indefinite wait */ + root_wait = -1; + + return 1; +} + +__setup("rootwait=", rootwait_timeout_setup); + +static char * __initdata root_mount_data; +static int __init root_data_setup(char *str) +{ + root_mount_data = str; + return 1; +} + +static char * __initdata root_fs_names; +static int __init fs_names_setup(char *str) +{ + root_fs_names = str; + return 1; +} + +static unsigned int __initdata root_delay; +static int __init root_delay_setup(char *str) +{ + if (kstrtouint(str, 0, &root_delay)) + return 0; + return 1; +} + +__setup("rootflags=", root_data_setup); +__setup("rootfstype=", fs_names_setup); +__setup("rootdelay=", root_delay_setup); + +/* This can return zero length strings. Caller should check */ +static int __init split_fs_names(char *page, size_t size) +{ + int count = 1; + char *p = page; + + strscpy(p, root_fs_names, size); + while (*p++) { + if (p[-1] == ',') { + p[-1] = '\0'; + count++; + } + } + + return count; +} + +static int __init do_mount_root(const char *name, const char *fs, + const int flags, const void *data) +{ + struct super_block *s; + char *data_page = NULL; + int ret; + + if (data) { + /* init_mount() requires a full page as fifth argument */ + data_page = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!data_page) + return -ENOMEM; + strscpy_pad(data_page, data, PAGE_SIZE); + } + + ret = init_mount(name, "/root", fs, flags, data_page); + if (ret) + goto out; + + init_chdir("/root"); + s = current->fs->pwd.dentry->d_sb; + ROOT_DEV = s->s_dev; + printk(KERN_INFO + "VFS: Mounted root (%s filesystem)%s on device %u:%u.\n", + s->s_type->name, + sb_rdonly(s) ? " readonly" : "", + MAJOR(ROOT_DEV), MINOR(ROOT_DEV)); + +out: + kfree(data_page); + return ret; +} + +void __init mount_root_generic(char *name, char *pretty_name, int flags) +{ + char *fs_names = kmalloc(PAGE_SIZE, GFP_KERNEL); + char *p; + char b[BDEVNAME_SIZE]; + int num_fs, i; + + if (!fs_names) + panic("VFS: Unable to mount root fs: not enough memory"); + + scnprintf(b, BDEVNAME_SIZE, "unknown-block(%u,%u)", + MAJOR(ROOT_DEV), MINOR(ROOT_DEV)); + if (root_fs_names) + num_fs = split_fs_names(fs_names, PAGE_SIZE); + else + num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE); +retry: + for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1) { + int err; + + if (!*p) + continue; + err = do_mount_root(name, p, flags, root_mount_data); + switch (err) { + case 0: + goto out; + case -EACCES: + case -EINVAL: +#ifdef CONFIG_BLOCK + init_flush_fput(); +#endif + continue; + } + /* + * Allow the user to distinguish between failed sys_open + * and bad superblock on root device. + * and give them a list of the available devices + */ + printk("VFS: Cannot open root device \"%s\" or %s: error %d\n", + pretty_name, b, err); + printk("Please append a correct \"root=\" boot option; here are the available partitions:\n"); + printk_all_partitions(); + + if (root_fs_names) + num_fs = list_bdev_fs_names(fs_names, PAGE_SIZE); + if (!num_fs) + pr_err("Can't find any bdev filesystem to be used for mount!\n"); + else { + pr_err("List of all bdev filesystems:\n"); + for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1) + pr_err(" %s", p); + pr_err("\n"); + } + + panic("VFS: Unable to mount root fs on %s", b); + } + if (!(flags & SB_RDONLY)) { + flags |= SB_RDONLY; + goto retry; + } + + printk("List of all partitions:\n"); + printk_all_partitions(); + printk("No filesystem could mount root, tried: "); + for (i = 0, p = fs_names; i < num_fs; i++, p += strlen(p)+1) + printk(" %s", p); + printk("\n"); + panic("VFS: Unable to mount root fs on \"%s\" or %s", pretty_name, b); +out: + kfree(fs_names); +} + +#ifdef CONFIG_ROOT_NFS + +#define NFSROOT_TIMEOUT_MIN 5 +#define NFSROOT_TIMEOUT_MAX 30 +#define NFSROOT_RETRY_MAX 5 + +static void __init mount_nfs_root(void) +{ + char *root_dev, *root_data; + unsigned int timeout; + int try; + + if (nfs_root_data(&root_dev, &root_data)) + goto fail; + + /* + * The server or network may not be ready, so try several + * times. Stop after a few tries in case the client wants + * to fall back to other boot methods. + */ + timeout = NFSROOT_TIMEOUT_MIN; + for (try = 1; ; try++) { + if (!do_mount_root(root_dev, "nfs", root_mountflags, root_data)) + return; + if (try > NFSROOT_RETRY_MAX) + break; + + /* Wait, in case the server refused us immediately */ + ssleep(timeout); + timeout <<= 1; + if (timeout > NFSROOT_TIMEOUT_MAX) + timeout = NFSROOT_TIMEOUT_MAX; + } +fail: + pr_err("VFS: Unable to mount root fs via NFS.\n"); +} +#else +static inline void mount_nfs_root(void) +{ +} +#endif /* CONFIG_ROOT_NFS */ + +#ifdef CONFIG_CIFS_ROOT + +#define CIFSROOT_TIMEOUT_MIN 5 +#define CIFSROOT_TIMEOUT_MAX 30 +#define CIFSROOT_RETRY_MAX 5 + +static void __init mount_cifs_root(void) +{ + char *root_dev, *root_data; + unsigned int timeout; + int try; + + if (cifs_root_data(&root_dev, &root_data)) + goto fail; + + timeout = CIFSROOT_TIMEOUT_MIN; + for (try = 1; ; try++) { + if (!do_mount_root(root_dev, "cifs", root_mountflags, + root_data)) + return; + if (try > CIFSROOT_RETRY_MAX) + break; + + ssleep(timeout); + timeout <<= 1; + if (timeout > CIFSROOT_TIMEOUT_MAX) + timeout = CIFSROOT_TIMEOUT_MAX; + } +fail: + pr_err("VFS: Unable to mount root fs via SMB.\n"); +} +#else +static inline void mount_cifs_root(void) +{ +} +#endif /* CONFIG_CIFS_ROOT */ + +static bool __init fs_is_nodev(char *fstype) +{ + struct file_system_type *fs = get_fs_type(fstype); + bool ret = false; + + if (fs) { + ret = !(fs->fs_flags & FS_REQUIRES_DEV); + put_filesystem(fs); + } + + return ret; +} + +static int __init mount_nodev_root(char *root_device_name) +{ + char *fs_names, *fstype; + int err = -EINVAL; + int num_fs, i; + + fs_names = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!fs_names) + return -EINVAL; + num_fs = split_fs_names(fs_names, PAGE_SIZE); + + for (i = 0, fstype = fs_names; i < num_fs; + i++, fstype += strlen(fstype) + 1) { + if (!*fstype) + continue; + if (!fs_is_nodev(fstype)) + continue; + err = do_mount_root(root_device_name, fstype, root_mountflags, + root_mount_data); + if (!err) + break; + } + + kfree(fs_names); + return err; +} + +#ifdef CONFIG_BLOCK +static void __init mount_block_root(char *root_device_name) +{ + int err = create_dev("/dev/root", ROOT_DEV); + + if (err < 0) + pr_emerg("Failed to create /dev/root: %d\n", err); + mount_root_generic("/dev/root", root_device_name, root_mountflags); +} +#else +static inline void mount_block_root(char *root_device_name) +{ +} +#endif /* CONFIG_BLOCK */ + +void __init mount_root(char *root_device_name) +{ + switch (ROOT_DEV) { + case Root_NFS: + mount_nfs_root(); + break; + case Root_CIFS: + mount_cifs_root(); + break; + case Root_Generic: + mount_root_generic(root_device_name, root_device_name, + root_mountflags); + break; + case 0: + if (root_device_name && root_fs_names && + mount_nodev_root(root_device_name) == 0) + break; + fallthrough; + default: + mount_block_root(root_device_name); + break; + } +} + +/* wait for any asynchronous scanning to complete */ +static void __init wait_for_root(char *root_device_name) +{ + ktime_t end; + + if (ROOT_DEV != 0) + return; + + pr_info("Waiting for root device %s...\n", root_device_name); + + end = ktime_add_ms(ktime_get_raw(), root_wait); + + while (!driver_probe_done() || + early_lookup_bdev(root_device_name, &ROOT_DEV) < 0) { + msleep(5); + if (root_wait > 0 && ktime_after(ktime_get_raw(), end)) + break; + } + + async_synchronize_full(); + +} + +static dev_t __init parse_root_device(char *root_device_name) +{ + int error; + dev_t dev; + + if (!strncmp(root_device_name, "mtd", 3) || + !strncmp(root_device_name, "ubi", 3)) + return Root_Generic; + if (strcmp(root_device_name, "/dev/nfs") == 0) + return Root_NFS; + if (strcmp(root_device_name, "/dev/cifs") == 0) + return Root_CIFS; + if (strcmp(root_device_name, "/dev/ram") == 0) + return Root_RAM0; + + error = early_lookup_bdev(root_device_name, &dev); + if (error) { + if (error == -EINVAL && root_wait) { + pr_err("Disabling rootwait; root= is invalid.\n"); + root_wait = 0; + } + return 0; + } + return dev; +} + +/* + * Prepare the namespace - decide what/where to mount, load ramdisks, etc. + */ +void __init prepare_namespace(void) +{ + if (root_delay) { + printk(KERN_INFO "Waiting %d sec before mounting root device...\n", + root_delay); + ssleep(root_delay); + } + + /* + * wait for the known devices to complete their probing + * + * Note: this is a potential source of long boot delays. + * For example, it is not atypical to wait 5 seconds here + * for the touchpad of a laptop to initialize. + */ + wait_for_device_probe(); + + md_run_setup(); + + if (saved_root_name[0]) + ROOT_DEV = parse_root_device(saved_root_name); + + initrd_load(); + + if (root_wait) + wait_for_root(saved_root_name); + mount_root(saved_root_name); + devtmpfs_mount(); + + if (init_pivot_root(".", ".")) { + pr_err("VFS: Failed to pivot into new rootfs\n"); + return; + } + if (init_umount(".", MNT_DETACH)) { + pr_err("VFS: Failed to unmount old rootfs\n"); + return; + } + pr_info("VFS: Pivoted into new rootfs\n"); +} + +static bool is_tmpfs; +static int rootfs_init_fs_context(struct fs_context *fc) +{ + if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs) + return shmem_init_fs_context(fc); + + return ramfs_init_fs_context(fc); +} + +struct file_system_type rootfs_fs_type = { + .name = "rootfs", + .init_fs_context = rootfs_init_fs_context, + .kill_sb = kill_anon_super, +}; + +void __init init_rootfs(void) +{ + if (IS_ENABLED(CONFIG_TMPFS)) { + if (!saved_root_name[0] && !root_fs_names) + is_tmpfs = true; + else if (root_fs_names && !!strstr(root_fs_names, "tmpfs")) + is_tmpfs = true; + } +} -- cgit v1.3.1