diff options
Diffstat (limited to 'fs/kernfs')
| -rw-r--r-- | fs/kernfs/dir.c | 191 | ||||
| -rw-r--r-- | fs/kernfs/mount.c | 69 |
2 files changed, 229 insertions, 31 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 118d033bcbbc..03b688d19f69 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -44,28 +44,122 @@ static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen) return strlcpy(buf, kn->parent ? kn->name : "/", buflen); } -static char * __must_check kernfs_path_locked(struct kernfs_node *kn, char *buf, - size_t buflen) +/* kernfs_node_depth - compute depth from @from to @to */ +static size_t kernfs_depth(struct kernfs_node *from, struct kernfs_node *to) { - char *p = buf + buflen; - int len; + size_t depth = 0; - *--p = '\0'; + while (to->parent && to != from) { + depth++; + to = to->parent; + } + return depth; +} - do { - len = strlen(kn->name); - if (p - buf < len + 1) { - buf[0] = '\0'; - p = NULL; - break; - } - p -= len; - memcpy(p, kn->name, len); - *--p = '/'; - kn = kn->parent; - } while (kn && kn->parent); +static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a, + struct kernfs_node *b) +{ + size_t da, db; + struct kernfs_root *ra = kernfs_root(a), *rb = kernfs_root(b); - return p; + if (ra != rb) + return NULL; + + da = kernfs_depth(ra->kn, a); + db = kernfs_depth(rb->kn, b); + + while (da > db) { + a = a->parent; + da--; + } + while (db > da) { + b = b->parent; + db--; + } + + /* worst case b and a will be the same at root */ + while (b != a) { + b = b->parent; + a = a->parent; + } + + return a; +} + +/** + * kernfs_path_from_node_locked - find a pseudo-absolute path to @kn_to, + * where kn_from is treated as root of the path. + * @kn_from: kernfs node which should be treated as root for the path + * @kn_to: kernfs node to which path is needed + * @buf: buffer to copy the path into + * @buflen: size of @buf + * + * We need to handle couple of scenarios here: + * [1] when @kn_from is an ancestor of @kn_to at some level + * kn_from: /n1/n2/n3 + * kn_to: /n1/n2/n3/n4/n5 + * result: /n4/n5 + * + * [2] when @kn_from is on a different hierarchy and we need to find common + * ancestor between @kn_from and @kn_to. + * kn_from: /n1/n2/n3/n4 + * kn_to: /n1/n2/n5 + * result: /../../n5 + * OR + * kn_from: /n1/n2/n3/n4/n5 [depth=5] + * kn_to: /n1/n2/n3 [depth=3] + * result: /../.. + * + * return value: length of the string. If greater than buflen, + * then contents of buf are undefined. On error, -1 is returned. + */ +static int kernfs_path_from_node_locked(struct kernfs_node *kn_to, + struct kernfs_node *kn_from, + char *buf, size_t buflen) +{ + struct kernfs_node *kn, *common; + const char parent_str[] = "/.."; + size_t depth_from, depth_to, len = 0, nlen = 0; + char *p; + int i; + + if (!kn_from) + kn_from = kernfs_root(kn_to)->kn; + + if (kn_from == kn_to) + return strlcpy(buf, "/", buflen); + + common = kernfs_common_ancestor(kn_from, kn_to); + if (WARN_ON(!common)) + return -1; + + depth_to = kernfs_depth(common, kn_to); + depth_from = kernfs_depth(common, kn_from); + + if (buf) + buf[0] = '\0'; + + for (i = 0; i < depth_from; i++) + len += strlcpy(buf + len, parent_str, + len < buflen ? buflen - len : 0); + + /* Calculate how many bytes we need for the rest */ + for (kn = kn_to; kn != common; kn = kn->parent) + nlen += strlen(kn->name) + 1; + + if (len + nlen >= buflen) + return len + nlen; + + p = buf + len + nlen; + *p = '\0'; + for (kn = kn_to; kn != common; kn = kn->parent) { + nlen = strlen(kn->name); + p -= nlen; + memcpy(p, kn->name, nlen); + *(--p) = '/'; + } + + return len + nlen; } /** @@ -115,6 +209,34 @@ size_t kernfs_path_len(struct kernfs_node *kn) } /** + * kernfs_path_from_node - build path of node @to relative to @from. + * @from: parent kernfs_node relative to which we need to build the path + * @to: kernfs_node of interest + * @buf: buffer to copy @to's path into + * @buflen: size of @buf + * + * Builds @to's path relative to @from in @buf. @from and @to must + * be on the same kernfs-root. If @from is not parent of @to, then a relative + * path (which includes '..'s) as needed to reach from @from to @to is + * returned. + * + * If @buf isn't long enough, the return value will be greater than @buflen + * and @buf contents are undefined. + */ +int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from, + char *buf, size_t buflen) +{ + unsigned long flags; + int ret; + + spin_lock_irqsave(&kernfs_rename_lock, flags); + ret = kernfs_path_from_node_locked(to, from, buf, buflen); + spin_unlock_irqrestore(&kernfs_rename_lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(kernfs_path_from_node); + +/** * kernfs_path - build full path of a given node * @kn: kernfs_node of interest * @buf: buffer to copy @kn's name into @@ -127,13 +249,12 @@ size_t kernfs_path_len(struct kernfs_node *kn) */ char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen) { - unsigned long flags; - char *p; + int ret; - spin_lock_irqsave(&kernfs_rename_lock, flags); - p = kernfs_path_locked(kn, buf, buflen); - spin_unlock_irqrestore(&kernfs_rename_lock, flags); - return p; + ret = kernfs_path_from_node(kn, NULL, buf, buflen); + if (ret < 0 || ret >= buflen) + return NULL; + return buf; } EXPORT_SYMBOL_GPL(kernfs_path); @@ -164,17 +285,25 @@ void pr_cont_kernfs_name(struct kernfs_node *kn) void pr_cont_kernfs_path(struct kernfs_node *kn) { unsigned long flags; - char *p; + int sz; spin_lock_irqsave(&kernfs_rename_lock, flags); - p = kernfs_path_locked(kn, kernfs_pr_cont_buf, - sizeof(kernfs_pr_cont_buf)); - if (p) - pr_cont("%s", p); - else - pr_cont("<name too long>"); + sz = kernfs_path_from_node_locked(kn, NULL, kernfs_pr_cont_buf, + sizeof(kernfs_pr_cont_buf)); + if (sz < 0) { + pr_cont("(error)"); + goto out; + } + + if (sz >= sizeof(kernfs_pr_cont_buf)) { + pr_cont("(name too long)"); + goto out; + } + + pr_cont("%s", kernfs_pr_cont_buf); +out: spin_unlock_irqrestore(&kernfs_rename_lock, flags); } diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index 8eaf417187f1..b67dbccdaf88 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -14,6 +14,7 @@ #include <linux/magic.h> #include <linux/slab.h> #include <linux/pagemap.h> +#include <linux/namei.h> #include "kernfs-internal.h" @@ -62,6 +63,74 @@ struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) 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)) + 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)) + return ERR_PTR(-EINVAL); + mutex_lock(&d_inode(dentry)->i_mutex); + dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name)); + mutex_unlock(&d_inode(dentry)->i_mutex); + 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); |