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-rw-r--r--fs/kernfs/dir.c210
-rw-r--r--fs/kernfs/mount.c88
2 files changed, 260 insertions, 38 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 996b7742c..37f9678ae 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);
+
+ 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) {
+ size_t tmp = strlen(kn->name);
+ p -= tmp;
+ memcpy(p, kn->name, tmp);
+ *(--p) = '/';
+ }
- return 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);
}
@@ -691,15 +820,22 @@ static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
const unsigned char *path,
const void *ns)
{
- static char path_buf[PATH_MAX]; /* protected by kernfs_mutex */
- size_t len = strlcpy(path_buf, path, PATH_MAX);
- char *p = path_buf;
- char *name;
+ size_t len;
+ char *p, *name;
lockdep_assert_held(&kernfs_mutex);
- if (len >= PATH_MAX)
+ /* grab kernfs_rename_lock to piggy back on kernfs_pr_cont_buf */
+ spin_lock_irq(&kernfs_rename_lock);
+
+ len = strlcpy(kernfs_pr_cont_buf, path, sizeof(kernfs_pr_cont_buf));
+
+ if (len >= sizeof(kernfs_pr_cont_buf)) {
+ spin_unlock_irq(&kernfs_rename_lock);
return NULL;
+ }
+
+ p = kernfs_pr_cont_buf;
while ((name = strsep(&p, "/")) && parent) {
if (*name == '\0')
@@ -707,6 +843,8 @@ static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
parent = kernfs_find_ns(parent, name, ns);
}
+ spin_unlock_irq(&kernfs_rename_lock);
+
return parent;
}
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 8eaf41718..3d670a367 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -14,6 +14,8 @@
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
+#include <linux/namei.h>
+#include <linux/seq_file.h>
#include "kernfs-internal.h"
@@ -39,6 +41,19 @@ static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
return 0;
}
+static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
+{
+ struct kernfs_node *node = dentry->d_fsdata;
+ 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,
@@ -46,6 +61,7 @@ const struct super_operations kernfs_sops = {
.remount_fs = kernfs_sop_remount_fs,
.show_options = kernfs_sop_show_options,
+ .show_path = kernfs_sop_show_path,
};
/**
@@ -62,6 +78,74 @@ 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);
@@ -69,8 +153,8 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
struct dentry *root;
info->sb = sb;
- sb->s_blocksize = PAGE_CACHE_SIZE;
- sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+ sb->s_blocksize = PAGE_SIZE;
+ sb->s_blocksize_bits = PAGE_SHIFT;
sb->s_magic = magic;
sb->s_op = &kernfs_sops;
sb->s_time_gran = 1;
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-19 10:12:53 +0000