From 76cb841cb886eef6b3bee341a2266c76578724ad Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 6 May 2024 03:02:30 +0200 Subject: Adding upstream version 4.19.249. Signed-off-by: Daniel Baumann --- fs/kernfs/mount.c | 421 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 421 insertions(+) create mode 100644 fs/kernfs/mount.c (limited to 'fs/kernfs/mount.c') diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c new file mode 100644 index 000000000..0b22c39da --- /dev/null +++ b/fs/kernfs/mount.c @@ -0,0 +1,421 @@ +/* + * fs/kernfs/mount.c - kernfs mount implementation + * + * Copyright (c) 2001-3 Patrick Mochel + * Copyright (c) 2007 SUSE Linux Products GmbH + * Copyright (c) 2007, 2013 Tejun Heo + * + * This file is released under the GPLv2. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "kernfs-internal.h" + +struct kmem_cache *kernfs_node_cache; + +static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data) +{ + struct kernfs_root *root = kernfs_info(sb)->root; + struct kernfs_syscall_ops *scops = root->syscall_ops; + + if (scops && scops->remount_fs) + return scops->remount_fs(root, flags, data); + return 0; +} + +static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry) +{ + struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry)); + struct kernfs_syscall_ops *scops = root->syscall_ops; + + if (scops && scops->show_options) + return scops->show_options(sf, root); + return 0; +} + +static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry) +{ + struct kernfs_node *node = kernfs_dentry_node(dentry); + struct kernfs_root *root = kernfs_root(node); + struct kernfs_syscall_ops *scops = root->syscall_ops; + + if (scops && scops->show_path) + return scops->show_path(sf, node, root); + + seq_dentry(sf, dentry, " \t\n\\"); + return 0; +} + +const struct super_operations kernfs_sops = { + .statfs = simple_statfs, + .drop_inode = generic_delete_inode, + .evict_inode = kernfs_evict_inode, + + .remount_fs = kernfs_sop_remount_fs, + .show_options = kernfs_sop_show_options, + .show_path = kernfs_sop_show_path, +}; + +/* + * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode + * number and generation + */ +struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root, + const union kernfs_node_id *id) +{ + struct kernfs_node *kn; + + kn = kernfs_find_and_get_node_by_ino(root, id->ino); + if (!kn) + return NULL; + if (kn->id.generation != id->generation) { + kernfs_put(kn); + return NULL; + } + return kn; +} + +static struct inode *kernfs_fh_get_inode(struct super_block *sb, + u64 ino, u32 generation) +{ + struct kernfs_super_info *info = kernfs_info(sb); + struct inode *inode; + struct kernfs_node *kn; + + if (ino == 0) + return ERR_PTR(-ESTALE); + + kn = kernfs_find_and_get_node_by_ino(info->root, ino); + if (!kn) + return ERR_PTR(-ESTALE); + inode = kernfs_get_inode(sb, kn); + kernfs_put(kn); + if (!inode) + return ERR_PTR(-ESTALE); + + if (generation && inode->i_generation != generation) { + /* we didn't find the right inode.. */ + iput(inode); + return ERR_PTR(-ESTALE); + } + return inode; +} + +static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid, + int fh_len, int fh_type) +{ + return generic_fh_to_dentry(sb, fid, fh_len, fh_type, + kernfs_fh_get_inode); +} + +static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid, + int fh_len, int fh_type) +{ + return generic_fh_to_parent(sb, fid, fh_len, fh_type, + kernfs_fh_get_inode); +} + +static struct dentry *kernfs_get_parent_dentry(struct dentry *child) +{ + struct kernfs_node *kn = kernfs_dentry_node(child); + + return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent)); +} + +static const struct export_operations kernfs_export_ops = { + .fh_to_dentry = kernfs_fh_to_dentry, + .fh_to_parent = kernfs_fh_to_parent, + .get_parent = kernfs_get_parent_dentry, +}; + +/** + * kernfs_root_from_sb - determine kernfs_root associated with a super_block + * @sb: the super_block in question + * + * Return the kernfs_root associated with @sb. If @sb is not a kernfs one, + * %NULL is returned. + */ +struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) +{ + if (sb->s_op == &kernfs_sops) + return kernfs_info(sb)->root; + return NULL; +} + +/* + * find the next ancestor in the path down to @child, where @parent was the + * ancestor whose descendant we want to find. + * + * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root + * node. If @parent is b, then we return the node for c. + * Passing in d as @parent is not ok. + */ +static struct kernfs_node *find_next_ancestor(struct kernfs_node *child, + struct kernfs_node *parent) +{ + if (child == parent) { + pr_crit_once("BUG in find_next_ancestor: called with parent == child"); + return NULL; + } + + while (child->parent != parent) { + if (!child->parent) + return NULL; + child = child->parent; + } + + return child; +} + +/** + * kernfs_node_dentry - get a dentry for the given kernfs_node + * @kn: kernfs_node for which a dentry is needed + * @sb: the kernfs super_block + */ +struct dentry *kernfs_node_dentry(struct kernfs_node *kn, + struct super_block *sb) +{ + struct dentry *dentry; + struct kernfs_node *knparent = NULL; + + BUG_ON(sb->s_op != &kernfs_sops); + + dentry = dget(sb->s_root); + + /* Check if this is the root kernfs_node */ + if (!kn->parent) + return dentry; + + knparent = find_next_ancestor(kn, NULL); + if (WARN_ON(!knparent)) { + dput(dentry); + return ERR_PTR(-EINVAL); + } + + do { + struct dentry *dtmp; + struct kernfs_node *kntmp; + + if (kn == knparent) + return dentry; + kntmp = find_next_ancestor(kn, knparent); + if (WARN_ON(!kntmp)) { + dput(dentry); + return ERR_PTR(-EINVAL); + } + dtmp = lookup_one_len_unlocked(kntmp->name, dentry, + strlen(kntmp->name)); + dput(dentry); + if (IS_ERR(dtmp)) + return dtmp; + knparent = kntmp; + dentry = dtmp; + } while (true); +} + +static int kernfs_fill_super(struct super_block *sb, unsigned long magic) +{ + struct kernfs_super_info *info = kernfs_info(sb); + struct inode *inode; + struct dentry *root; + + info->sb = sb; + /* Userspace would break if executables or devices appear on sysfs */ + sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV; + sb->s_blocksize = PAGE_SIZE; + sb->s_blocksize_bits = PAGE_SHIFT; + sb->s_magic = magic; + sb->s_op = &kernfs_sops; + sb->s_xattr = kernfs_xattr_handlers; + if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP) + sb->s_export_op = &kernfs_export_ops; + sb->s_time_gran = 1; + + /* get root inode, initialize and unlock it */ + mutex_lock(&kernfs_mutex); + inode = kernfs_get_inode(sb, info->root->kn); + mutex_unlock(&kernfs_mutex); + if (!inode) { + pr_debug("kernfs: could not get root inode\n"); + return -ENOMEM; + } + + /* instantiate and link root dentry */ + root = d_make_root(inode); + if (!root) { + pr_debug("%s: could not get root dentry!\n", __func__); + return -ENOMEM; + } + sb->s_root = root; + sb->s_d_op = &kernfs_dops; + return 0; +} + +static int kernfs_test_super(struct super_block *sb, void *data) +{ + struct kernfs_super_info *sb_info = kernfs_info(sb); + struct kernfs_super_info *info = data; + + return sb_info->root == info->root && sb_info->ns == info->ns; +} + +static int kernfs_set_super(struct super_block *sb, void *data) +{ + int error; + error = set_anon_super(sb, data); + if (!error) + sb->s_fs_info = data; + return error; +} + +/** + * kernfs_super_ns - determine the namespace tag of a kernfs super_block + * @sb: super_block of interest + * + * Return the namespace tag associated with kernfs super_block @sb. + */ +const void *kernfs_super_ns(struct super_block *sb) +{ + struct kernfs_super_info *info = kernfs_info(sb); + + return info->ns; +} + +/** + * kernfs_mount_ns - kernfs mount helper + * @fs_type: file_system_type of the fs being mounted + * @flags: mount flags specified for the mount + * @root: kernfs_root of the hierarchy being mounted + * @magic: file system specific magic number + * @new_sb_created: tell the caller if we allocated a new superblock + * @ns: optional namespace tag of the mount + * + * This is to be called from each kernfs user's file_system_type->mount() + * implementation, which should pass through the specified @fs_type and + * @flags, and specify the hierarchy and namespace tag to mount via @root + * and @ns, respectively. + * + * The return value can be passed to the vfs layer verbatim. + */ +struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, + struct kernfs_root *root, unsigned long magic, + bool *new_sb_created, const void *ns) +{ + struct super_block *sb; + struct kernfs_super_info *info; + int error; + + info = kzalloc(sizeof(*info), GFP_KERNEL); + if (!info) + return ERR_PTR(-ENOMEM); + + info->root = root; + info->ns = ns; + INIT_LIST_HEAD(&info->node); + + sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags, + &init_user_ns, info); + if (IS_ERR(sb) || sb->s_fs_info != info) + kfree(info); + if (IS_ERR(sb)) + return ERR_CAST(sb); + + if (new_sb_created) + *new_sb_created = !sb->s_root; + + if (!sb->s_root) { + struct kernfs_super_info *info = kernfs_info(sb); + + error = kernfs_fill_super(sb, magic); + if (error) { + deactivate_locked_super(sb); + return ERR_PTR(error); + } + sb->s_flags |= SB_ACTIVE; + + mutex_lock(&kernfs_mutex); + list_add(&info->node, &root->supers); + mutex_unlock(&kernfs_mutex); + } + + return dget(sb->s_root); +} + +/** + * kernfs_kill_sb - kill_sb for kernfs + * @sb: super_block being killed + * + * This can be used directly for file_system_type->kill_sb(). If a kernfs + * user needs extra cleanup, it can implement its own kill_sb() and call + * this function at the end. + */ +void kernfs_kill_sb(struct super_block *sb) +{ + struct kernfs_super_info *info = kernfs_info(sb); + + mutex_lock(&kernfs_mutex); + list_del(&info->node); + mutex_unlock(&kernfs_mutex); + + /* + * Remove the superblock from fs_supers/s_instances + * so we can't find it, before freeing kernfs_super_info. + */ + kill_anon_super(sb); + kfree(info); +} + +/** + * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root + * @kernfs_root: the kernfs_root in question + * @ns: the namespace tag + * + * Pin the superblock so the superblock won't be destroyed in subsequent + * operations. This can be used to block ->kill_sb() which may be useful + * for kernfs users which dynamically manage superblocks. + * + * Returns NULL if there's no superblock associated to this kernfs_root, or + * -EINVAL if the superblock is being freed. + */ +struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns) +{ + struct kernfs_super_info *info; + struct super_block *sb = NULL; + + mutex_lock(&kernfs_mutex); + list_for_each_entry(info, &root->supers, node) { + if (info->ns == ns) { + sb = info->sb; + if (!atomic_inc_not_zero(&info->sb->s_active)) + sb = ERR_PTR(-EINVAL); + break; + } + } + mutex_unlock(&kernfs_mutex); + return sb; +} + +void __init kernfs_init(void) +{ + + /* + * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino + * can access the slab lock free. This could introduce stale nodes, + * please see how kernfs_find_and_get_node_by_ino filters out stale + * nodes. + */ + kernfs_node_cache = kmem_cache_create("kernfs_node_cache", + sizeof(struct kernfs_node), + 0, + SLAB_PANIC | SLAB_TYPESAFE_BY_RCU, + NULL); +} -- cgit v1.2.3