[patch 1/7] vfs: mountinfo: add dentry_path()

[mszeredi@suse.cz] split big patch into managable chunks

Add the following functions:

  dentry_path()
  seq_dentry()

These are similar to d_path() and seq_path().  But instead of
calculating the path within a mount namespace, they calculate the path
from the root of the filesystem to a given dentry, ignoring mounts
completely.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 115 insertions, 40 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 43455776711e..635c2aa427ed 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1746,6 +1746,17 @@ shouldnt_be_hashed:
         goto shouldnt_be_hashed;
 }
 
+static int prepend(char **buffer, int *buflen, const char *str,
+                          int namelen)
+{
+        *buflen -= namelen;
+        if (*buflen < 0)
+                return -ENAMETOOLONG;
+        *buffer -= namelen;
+        memcpy(*buffer, str, namelen);
+        return 0;
+}
+
 /**
  * d_path - return the path of a dentry
  * @dentry: dentry to report
@@ -1767,17 +1778,11 @@ static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
 {
         char * end = buffer+buflen;
         char * retval;
-        int namelen;
-
-        *--end = '\0';
-        buflen--;
-        if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
-                buflen -= 10;
-                end -= 10;
-                if (buflen < 0)
+
+        prepend(&end, &buflen, "\0", 1);
+        if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
+                (prepend(&end, &buflen, " (deleted)", 10) != 0))
                         goto Elong;
-                memcpy(end, " (deleted)", 10);
-        }
 
         if (buflen < 1)
                 goto Elong;
@@ -1804,13 +1809,10 @@ static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
                 }
                 parent = dentry->d_parent;
                 prefetch(parent);
-                namelen = dentry->d_name.len;
-                buflen -= namelen + 1;
-                if (buflen < 0)
+                if ((prepend(&end, &buflen, dentry->d_name.name,
+                                dentry->d_name.len) != 0) ||
+                    (prepend(&end, &buflen, "/", 1) != 0))
                         goto Elong;
-                end -= namelen;
-                memcpy(end, dentry->d_name.name, namelen);
-                *--end = '/';
                 retval = end;
                 dentry = parent;
         }
@@ -1818,12 +1820,10 @@ static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
         return retval;
 
 global_root:
-        namelen = dentry->d_name.len;
-        buflen -= namelen;
-        if (buflen < 0)
+        retval += 1;    /* hit the slash */
+        if (prepend(&retval, &buflen, dentry->d_name.name,
+                    dentry->d_name.len) != 0)
                 goto Elong;
-        retval -= namelen-1;    /* hit the slash */
-        memcpy(retval, dentry->d_name.name, namelen);
         return retval;
 Elong:
         return ERR_PTR(-ENAMETOOLONG);
@@ -1859,7 +1859,7 @@ char *d_path(struct path *path, char *buf, int buflen)
 
         read_lock(&current->fs->lock);
         root = current->fs->root;
-        path_get(&current->fs->root);
+        path_get(&root);
         read_unlock(&current->fs->lock);
         spin_lock(&dcache_lock);
         res = __d_path(path->dentry, path->mnt, &root, buf, buflen);
@@ -1890,6 +1890,48 @@ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
 }
 
 /*
+ * Write full pathname from the root of the filesystem into the buffer.
+ */
+char *dentry_path(struct dentry *dentry, char *buf, int buflen)
+{
+        char *end = buf + buflen;
+        char *retval;
+
+        spin_lock(&dcache_lock);
+        prepend(&end, &buflen, "\0", 1);
+        if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
+                (prepend(&end, &buflen, "//deleted", 9) != 0))
+                        goto Elong;
+        if (buflen < 1)
+                goto Elong;
+        /* Get '/' right */
+        retval = end-1;
+        *retval = '/';
+
+        for (;;) {
+                struct dentry *parent;
+                if (IS_ROOT(dentry))
+                        break;
+
+                parent = dentry->d_parent;
+                prefetch(parent);
+
+                if ((prepend(&end, &buflen, dentry->d_name.name,
+                                dentry->d_name.len) != 0) ||
+                    (prepend(&end, &buflen, "/", 1) != 0))
+                        goto Elong;
+
+                retval = end;
+                dentry = parent;
+        }
+        spin_unlock(&dcache_lock);
+        return retval;
+Elong:
+        spin_unlock(&dcache_lock);
+        return ERR_PTR(-ENAMETOOLONG);
+}
+
+/*
  * NOTE! The user-level library version returns a
  * character pointer. The kernel system call just
  * returns the length of the buffer filled (which
@@ -1918,9 +1960,9 @@ asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
 
         read_lock(&current->fs->lock);
         pwd = current->fs->pwd;
-        path_get(&current->fs->pwd);
+        path_get(&pwd);
         root = current->fs->root;
-        path_get(&current->fs->root);
+        path_get(&root);
         read_unlock(&current->fs->lock);
 
         error = -ENOENT;
diff --git a/fs/seq_file.c b/fs/seq_file.c
index cdfd996ca6ef..ae59f5a6c5c1 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -350,28 +350,40 @@ int seq_printf(struct seq_file *m, const char *f, ...)
 }
 EXPORT_SYMBOL(seq_printf);
 
+static char *mangle_path(char *s, char *p, char *esc)
+{
+        while (s <= p) {
+                char c = *p++;
+                if (!c) {
+                        return s;
+                } else if (!strchr(esc, c)) {
+                        *s++ = c;
+                } else if (s + 4 > p) {
+                        break;
+                } else {
+                        *s++ = '\\';
+                        *s++ = '0' + ((c & 0300) >> 6);
+                        *s++ = '0' + ((c & 070) >> 3);
+                        *s++ = '0' + (c & 07);
+                }
+        }
+        return NULL;
+}
+
+/*
+ * return the absolute path of 'dentry' residing in mount 'mnt'.
+ */
 int seq_path(struct seq_file *m, struct path *path, char *esc)
 {
         if (m->count < m->size) {
                 char *s = m->buf + m->count;
                 char *p = d_path(path, s, m->size - m->count);
                 if (!IS_ERR(p)) {
-                        while (s <= p) {
-                                char c = *p++;
-                                if (!c) {
-                                        p = m->buf + m->count;
-                                        m->count = s - m->buf;
-                                        return s - p;
-                                } else if (!strchr(esc, c)) {
-                                        *s++ = c;
-                                } else if (s + 4 > p) {
-                                        break;
-                                } else {
-                                        *s++ = '\\';
-                                        *s++ = '0' + ((c & 0300) >> 6);
-                                        *s++ = '0' + ((c & 070) >> 3);
-                                        *s++ = '0' + (c & 07);
-                                }
+                        s = mangle_path(s, p, esc);
+                        if (s) {
+                                p = m->buf + m->count;
+                                m->count = s - m->buf;
+                                return s - p;
                         }
                 }
         }
@@ -380,6 +392,27 @@ int seq_path(struct seq_file *m, struct path *path, char *esc)
 }
 EXPORT_SYMBOL(seq_path);
 
+/*
+ * returns the path of the 'dentry' from the root of its filesystem.
+ */
+int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
+{
+        if (m->count < m->size) {
+                char *s = m->buf + m->count;
+                char *p = dentry_path(dentry, s, m->size - m->count);
+                if (!IS_ERR(p)) {
+                        s = mangle_path(s, p, esc);
+                        if (s) {
+                                p = m->buf + m->count;
+                                m->count = s - m->buf;
+                                return s - p;
+                        }
+                }
+        }
+        m->count = m->size;
+        return -1;
+}
+
 static void *single_start(struct seq_file *p, loff_t *pos)
 {
         return NULL + (*pos == 0);