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397 lines
9.6 KiB
397 lines
9.6 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* fs/kernfs/mount.c - kernfs mount implementation |
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* |
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* Copyright (c) 2001-3 Patrick Mochel |
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* Copyright (c) 2007 SUSE Linux Products GmbH |
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* Copyright (c) 2007, 2013 Tejun Heo <[email protected]> |
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*/ |
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#include <linux/fs.h> |
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#include <linux/mount.h> |
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#include <linux/init.h> |
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#include <linux/magic.h> |
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#include <linux/slab.h> |
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#include <linux/pagemap.h> |
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#include <linux/namei.h> |
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#include <linux/seq_file.h> |
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#include <linux/exportfs.h> |
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#include "kernfs-internal.h" |
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struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache; |
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static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry) |
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{ |
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struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry)); |
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struct kernfs_syscall_ops *scops = root->syscall_ops; |
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if (scops && scops->show_options) |
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return scops->show_options(sf, root); |
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return 0; |
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} |
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static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry) |
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{ |
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struct kernfs_node *node = kernfs_dentry_node(dentry); |
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struct kernfs_root *root = kernfs_root(node); |
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struct kernfs_syscall_ops *scops = root->syscall_ops; |
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if (scops && scops->show_path) |
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return scops->show_path(sf, node, root); |
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seq_dentry(sf, dentry, " \t\n\\"); |
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return 0; |
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} |
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const struct super_operations kernfs_sops = { |
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.statfs = simple_statfs, |
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.drop_inode = generic_delete_inode, |
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.evict_inode = kernfs_evict_inode, |
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.show_options = kernfs_sop_show_options, |
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.show_path = kernfs_sop_show_path, |
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}; |
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static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len, |
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struct inode *parent) |
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{ |
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struct kernfs_node *kn = inode->i_private; |
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if (*max_len < 2) { |
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*max_len = 2; |
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return FILEID_INVALID; |
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} |
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*max_len = 2; |
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*(u64 *)fh = kn->id; |
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return FILEID_KERNFS; |
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} |
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static struct dentry *__kernfs_fh_to_dentry(struct super_block *sb, |
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struct fid *fid, int fh_len, |
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int fh_type, bool get_parent) |
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{ |
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struct kernfs_super_info *info = kernfs_info(sb); |
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struct kernfs_node *kn; |
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struct inode *inode; |
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u64 id; |
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if (fh_len < 2) |
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return NULL; |
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switch (fh_type) { |
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case FILEID_KERNFS: |
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id = *(u64 *)fid; |
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break; |
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case FILEID_INO32_GEN: |
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case FILEID_INO32_GEN_PARENT: |
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/* |
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* blk_log_action() exposes "LOW32,HIGH32" pair without |
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* type and userland can call us with generic fid |
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* constructed from them. Combine it back to ID. See |
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* blk_log_action(). |
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*/ |
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id = ((u64)fid->i32.gen << 32) | fid->i32.ino; |
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break; |
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default: |
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return NULL; |
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} |
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kn = kernfs_find_and_get_node_by_id(info->root, id); |
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if (!kn) |
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return ERR_PTR(-ESTALE); |
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if (get_parent) { |
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struct kernfs_node *parent; |
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parent = kernfs_get_parent(kn); |
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kernfs_put(kn); |
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kn = parent; |
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if (!kn) |
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return ERR_PTR(-ESTALE); |
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} |
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inode = kernfs_get_inode(sb, kn); |
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kernfs_put(kn); |
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if (!inode) |
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return ERR_PTR(-ESTALE); |
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return d_obtain_alias(inode); |
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} |
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static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, |
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struct fid *fid, int fh_len, |
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int fh_type) |
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{ |
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return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false); |
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} |
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static struct dentry *kernfs_fh_to_parent(struct super_block *sb, |
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struct fid *fid, int fh_len, |
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int fh_type) |
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{ |
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return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true); |
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} |
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static struct dentry *kernfs_get_parent_dentry(struct dentry *child) |
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{ |
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struct kernfs_node *kn = kernfs_dentry_node(child); |
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return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent)); |
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} |
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static const struct export_operations kernfs_export_ops = { |
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.encode_fh = kernfs_encode_fh, |
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.fh_to_dentry = kernfs_fh_to_dentry, |
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.fh_to_parent = kernfs_fh_to_parent, |
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.get_parent = kernfs_get_parent_dentry, |
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}; |
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/** |
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* kernfs_root_from_sb - determine kernfs_root associated with a super_block |
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* @sb: the super_block in question |
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* |
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* Return the kernfs_root associated with @sb. If @sb is not a kernfs one, |
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* %NULL is returned. |
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*/ |
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struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) |
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{ |
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if (sb->s_op == &kernfs_sops) |
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return kernfs_info(sb)->root; |
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return NULL; |
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} |
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/* |
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* find the next ancestor in the path down to @child, where @parent was the |
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* ancestor whose descendant we want to find. |
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* |
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* Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root |
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* node. If @parent is b, then we return the node for c. |
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* Passing in d as @parent is not ok. |
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*/ |
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static struct kernfs_node *find_next_ancestor(struct kernfs_node *child, |
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struct kernfs_node *parent) |
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{ |
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if (child == parent) { |
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pr_crit_once("BUG in find_next_ancestor: called with parent == child"); |
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return NULL; |
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} |
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while (child->parent != parent) { |
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if (!child->parent) |
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return NULL; |
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child = child->parent; |
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} |
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return child; |
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} |
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/** |
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* kernfs_node_dentry - get a dentry for the given kernfs_node |
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* @kn: kernfs_node for which a dentry is needed |
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* @sb: the kernfs super_block |
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*/ |
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struct dentry *kernfs_node_dentry(struct kernfs_node *kn, |
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struct super_block *sb) |
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{ |
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struct dentry *dentry; |
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struct kernfs_node *knparent = NULL; |
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BUG_ON(sb->s_op != &kernfs_sops); |
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dentry = dget(sb->s_root); |
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/* Check if this is the root kernfs_node */ |
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if (!kn->parent) |
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return dentry; |
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knparent = find_next_ancestor(kn, NULL); |
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if (WARN_ON(!knparent)) { |
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dput(dentry); |
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return ERR_PTR(-EINVAL); |
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} |
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do { |
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struct dentry *dtmp; |
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struct kernfs_node *kntmp; |
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if (kn == knparent) |
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return dentry; |
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kntmp = find_next_ancestor(kn, knparent); |
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if (WARN_ON(!kntmp)) { |
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dput(dentry); |
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return ERR_PTR(-EINVAL); |
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} |
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dtmp = lookup_positive_unlocked(kntmp->name, dentry, |
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strlen(kntmp->name)); |
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dput(dentry); |
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if (IS_ERR(dtmp)) |
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return dtmp; |
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knparent = kntmp; |
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dentry = dtmp; |
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} while (true); |
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} |
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static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc) |
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{ |
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struct kernfs_super_info *info = kernfs_info(sb); |
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struct inode *inode; |
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struct dentry *root; |
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info->sb = sb; |
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/* Userspace would break if executables or devices appear on sysfs */ |
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sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV; |
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sb->s_blocksize = PAGE_SIZE; |
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sb->s_blocksize_bits = PAGE_SHIFT; |
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sb->s_magic = kfc->magic; |
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sb->s_op = &kernfs_sops; |
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sb->s_xattr = kernfs_xattr_handlers; |
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if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP) |
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sb->s_export_op = &kernfs_export_ops; |
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sb->s_time_gran = 1; |
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/* sysfs dentries and inodes don't require IO to create */ |
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sb->s_shrink.seeks = 0; |
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/* get root inode, initialize and unlock it */ |
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mutex_lock(&kernfs_mutex); |
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inode = kernfs_get_inode(sb, info->root->kn); |
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mutex_unlock(&kernfs_mutex); |
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if (!inode) { |
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pr_debug("kernfs: could not get root inode\n"); |
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return -ENOMEM; |
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} |
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/* instantiate and link root dentry */ |
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root = d_make_root(inode); |
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if (!root) { |
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pr_debug("%s: could not get root dentry!\n", __func__); |
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return -ENOMEM; |
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} |
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sb->s_root = root; |
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sb->s_d_op = &kernfs_dops; |
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return 0; |
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} |
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static int kernfs_test_super(struct super_block *sb, struct fs_context *fc) |
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{ |
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struct kernfs_super_info *sb_info = kernfs_info(sb); |
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struct kernfs_super_info *info = fc->s_fs_info; |
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return sb_info->root == info->root && sb_info->ns == info->ns; |
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} |
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static int kernfs_set_super(struct super_block *sb, struct fs_context *fc) |
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{ |
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struct kernfs_fs_context *kfc = fc->fs_private; |
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kfc->ns_tag = NULL; |
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return set_anon_super_fc(sb, fc); |
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} |
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/** |
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* kernfs_super_ns - determine the namespace tag of a kernfs super_block |
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* @sb: super_block of interest |
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* |
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* Return the namespace tag associated with kernfs super_block @sb. |
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*/ |
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const void *kernfs_super_ns(struct super_block *sb) |
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{ |
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struct kernfs_super_info *info = kernfs_info(sb); |
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return info->ns; |
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} |
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/** |
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* kernfs_get_tree - kernfs filesystem access/retrieval helper |
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* @fc: The filesystem context. |
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* |
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* This is to be called from each kernfs user's fs_context->ops->get_tree() |
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* implementation, which should set the specified ->@fs_type and ->@flags, and |
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* specify the hierarchy and namespace tag to mount via ->@root and ->@ns, |
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* respectively. |
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*/ |
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int kernfs_get_tree(struct fs_context *fc) |
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{ |
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struct kernfs_fs_context *kfc = fc->fs_private; |
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struct super_block *sb; |
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struct kernfs_super_info *info; |
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int error; |
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info = kzalloc(sizeof(*info), GFP_KERNEL); |
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if (!info) |
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return -ENOMEM; |
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info->root = kfc->root; |
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info->ns = kfc->ns_tag; |
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INIT_LIST_HEAD(&info->node); |
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fc->s_fs_info = info; |
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sb = sget_fc(fc, kernfs_test_super, kernfs_set_super); |
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if (IS_ERR(sb)) |
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return PTR_ERR(sb); |
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if (!sb->s_root) { |
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struct kernfs_super_info *info = kernfs_info(sb); |
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kfc->new_sb_created = true; |
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error = kernfs_fill_super(sb, kfc); |
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if (error) { |
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deactivate_locked_super(sb); |
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return error; |
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} |
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sb->s_flags |= SB_ACTIVE; |
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mutex_lock(&kernfs_mutex); |
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list_add(&info->node, &info->root->supers); |
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mutex_unlock(&kernfs_mutex); |
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} |
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fc->root = dget(sb->s_root); |
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return 0; |
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} |
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void kernfs_free_fs_context(struct fs_context *fc) |
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{ |
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/* Note that we don't deal with kfc->ns_tag here. */ |
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kfree(fc->s_fs_info); |
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fc->s_fs_info = NULL; |
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} |
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/** |
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* kernfs_kill_sb - kill_sb for kernfs |
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* @sb: super_block being killed |
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* |
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* This can be used directly for file_system_type->kill_sb(). If a kernfs |
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* user needs extra cleanup, it can implement its own kill_sb() and call |
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* this function at the end. |
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*/ |
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void kernfs_kill_sb(struct super_block *sb) |
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{ |
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struct kernfs_super_info *info = kernfs_info(sb); |
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mutex_lock(&kernfs_mutex); |
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list_del(&info->node); |
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mutex_unlock(&kernfs_mutex); |
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/* |
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* Remove the superblock from fs_supers/s_instances |
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* so we can't find it, before freeing kernfs_super_info. |
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*/ |
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kill_anon_super(sb); |
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kfree(info); |
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} |
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void __init kernfs_init(void) |
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{ |
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kernfs_node_cache = kmem_cache_create("kernfs_node_cache", |
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sizeof(struct kernfs_node), |
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0, SLAB_PANIC, NULL); |
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/* Creates slab cache for kernfs inode attributes */ |
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kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache", |
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sizeof(struct kernfs_iattrs), |
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0, SLAB_PANIC, NULL); |
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}
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