[patch 2/7] vfs: mountinfo: add seq_file_root()

Add a new function:

  seq_file_root()

This is similar to seq_path(), but calculates the path relative to the
given root, instead of current->fs->root.  If the path was unreachable
from root, then modify the root parameter to reflect this.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/dcache.c b/fs/dcache.c
index 635c2aa..3ee588d 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1759,10 +1759,8 @@ static int prepend(char **buffer, int *buflen, const char *str,
 
 /**
  * d_path - return the path of a dentry
- * @dentry: dentry to report
- * @vfsmnt: vfsmnt to which the dentry belongs
- * @root: root dentry
- * @rootmnt: vfsmnt to which the root dentry belongs
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry (may be modified by this function)
  * @buffer: buffer to return value in
  * @buflen: buffer length
  *
@@ -1772,10 +1770,15 @@ static int prepend(char **buffer, int *buflen, const char *str,
  * Returns the buffer or an error code if the path was too long.
  *
  * "buflen" should be positive. Caller holds the dcache_lock.
+ *
+ * If path is not reachable from the supplied root, then the value of
+ * root is changed (without modifying refcounts).
  */
-static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
-                      struct path *root, char *buffer, int buflen)
+char *__d_path(const struct path *path, struct path *root,
+              char *buffer, int buflen)
 {
+       struct dentry *dentry = path->dentry;
+       struct vfsmount *vfsmnt = path->mnt;
        char * end = buffer+buflen;
        char * retval;
 
@@ -1824,6 +1827,8 @@ global_root:
        if (prepend(&retval, &buflen, dentry->d_name.name,
                    dentry->d_name.len) != 0)
                goto Elong;
+       root->mnt = vfsmnt;
+       root->dentry = dentry;
        return retval;
 Elong:
        return ERR_PTR(-ENAMETOOLONG);
@@ -1846,6 +1851,7 @@ char *d_path(struct path *path, char *buf, int buflen)
 {
        char *res;
        struct path root;
+       struct path tmp;
 
        /*
         * We have various synthetic filesystems that never get mounted.  On
@@ -1862,7 +1868,8 @@ char *d_path(struct path *path, char *buf, int buflen)
        path_get(&root);
        read_unlock(&current->fs->lock);
        spin_lock(&dcache_lock);
-       res = __d_path(path->dentry, path->mnt, &root, buf, buflen);
+       tmp = root;
+       res = __d_path(path, &tmp, buf, buflen);
        spin_unlock(&dcache_lock);
        path_put(&root);
        return res;
@@ -1970,9 +1977,10 @@ asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
        spin_lock(&dcache_lock);
        if (pwd.dentry->d_parent == pwd.dentry || !d_unhashed(pwd.dentry)) {
                unsigned long len;
+               struct path tmp = root;
                char * cwd;
 
-               cwd = __d_path(pwd.dentry, pwd.mnt, &root, page, PAGE_SIZE);
+               cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
                spin_unlock(&dcache_lock);
 
                error = PTR_ERR(cwd);

diff --git a/fs/seq_file.c b/fs/seq_file.c
index ae59f5a..3f54dbd 100644 (file)
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -393,6 +393,36 @@ int seq_path(struct seq_file *m, struct path *path, char *esc)
 EXPORT_SYMBOL(seq_path);
 
 /*
+ * Same as seq_path, but relative to supplied root.
+ *
+ * root may be changed, see __d_path().
+ */
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+                 char *esc)
+{
+       int err = -ENAMETOOLONG;
+       if (m->count < m->size) {
+               char *s = m->buf + m->count;
+               char *p;
+
+               spin_lock(&dcache_lock);
+               p = __d_path(path, root, s, m->size - m->count);
+               spin_unlock(&dcache_lock);
+               err = PTR_ERR(p);
+               if (!IS_ERR(p)) {
+                       s = mangle_path(s, p, esc);
+                       if (s) {
+                               p = m->buf + m->count;
+                               m->count = s - m->buf;
+                               return 0;
+                       }
+               }
+       }
+       m->count = m->size;
+       return err;
+}
+
+/*
  * returns the path of the 'dentry' from the root of its filesystem.
  */
 int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 6396003..cfb1627 100644 (file)
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -301,6 +301,7 @@ extern int d_validate(struct dentry *, struct dentry *);
  */
 extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
 
+extern char *__d_path(const struct path *path, struct path *root, char *, int);
 extern char *d_path(struct path *, char *, int);
 extern char *dentry_path(struct dentry *, char *, int);
 

diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 11676cc..5b5369c 100644 (file)
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -46,6 +46,8 @@ int seq_printf(struct seq_file *, const char *, ...)
 
 int seq_path(struct seq_file *, struct path *, char *);
 int seq_dentry(struct seq_file *, struct dentry *, char *);
+int seq_path_root(struct seq_file *m, struct path *path, struct path *root,
+                 char *esc);
 
 int single_open(struct file *, int (*)(struct seq_file *, void *), void *);
 int single_release(struct inode *, struct file *);