Revert "[PATCH] Fix d_path for lazy unmounts"

This reverts commit eb3dfb0cb1f4a44e2d0553f89514ce9f2a9fcaf1.

It causes some strange Gnome problem with dbus-daemon getting stuck, so
we'll revert it until that problem is understood.

Reported by both walt and Greg KH, who both independently git-bisected
the problem to this commit.

Andreas is looking at it.

Reported-by: walt <wa1ter@myrealbox.com>
Reported-by: Greg KH <greg@kroah.com>
Acked-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 70 insertions, 80 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index b5f613932912..d68631f18df1 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1739,41 +1739,45 @@ shouldnt_be_hashed:
  * @rootmnt: vfsmnt to which the root dentry belongs
  * @buffer: buffer to return value in
  * @buflen: buffer length
- * @fail_deleted: what to return for deleted files
  *
- * Convert a dentry into an ASCII path name. If the entry has been deleted,
- * then if @fail_deleted is true, ERR_PTR(-ENOENT) is returned. Otherwise,
- * the the string " (deleted)" is appended. Note that this is ambiguous.
+ * Convert a dentry into an ASCII path name. If the entry has been deleted
+ * the string " (deleted)" is appended. Note that this is ambiguous.
  *
- * Returns the buffer or an error code.
+ * Returns the buffer or an error code if the path was too long.
+ *
+ * "buflen" should be positive. Caller holds the dcache_lock.
  */
-static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
-                      struct dentry *root, struct vfsmount *rootmnt,
-                      char *buffer, int buflen, int fail_deleted)
+static char * __d_path( struct dentry *dentry, struct vfsmount *vfsmnt,
+                        struct dentry *root, struct vfsmount *rootmnt,
+                        char *buffer, int buflen)
 {
-        int namelen, is_slash;
-
-        if (buflen < 2)
-                return ERR_PTR(-ENAMETOOLONG);
-        buffer += --buflen;
-        *buffer = '\0';
+        char * end = buffer+buflen;
+        char * retval;
+        int namelen;
 
-        spin_lock(&dcache_lock);
+        *--end = '\0';
+        buflen--;
         if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
-                if (fail_deleted) {
-                        buffer = ERR_PTR(-ENOENT);
-                        goto out;
-                }
-                if (buflen < 10)
-                        goto Elong;
                 buflen -= 10;
-                buffer -= 10;
-                memcpy(buffer, " (deleted)", 10);
+                end -= 10;
+                if (buflen < 0)
+                        goto Elong;
+                memcpy(end, " (deleted)", 10);
         }
-        while (dentry != root || vfsmnt != rootmnt) {
+
+        if (buflen < 1)
+                goto Elong;
+        /* Get '/' right */
+        retval = end-1;
+        *retval = '/';
+
+        for (;;) {
                 struct dentry * parent;
 
+                if (dentry == root && vfsmnt == rootmnt)
+                        break;
                 if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+                        /* Global root? */
                         spin_lock(&vfsmount_lock);
                         if (vfsmnt->mnt_parent == vfsmnt) {
                                 spin_unlock(&vfsmount_lock);
@@ -1787,60 +1791,33 @@ static char *__d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
                 parent = dentry->d_parent;
                 prefetch(parent);
                 namelen = dentry->d_name.len;
-                if (buflen <= namelen)
-                        goto Elong;
                 buflen -= namelen + 1;
-                buffer -= namelen;
-                memcpy(buffer, dentry->d_name.name, namelen);
-                *--buffer = '/';
+                if (buflen < 0)
+                        goto Elong;
+                end -= namelen;
+                memcpy(end, dentry->d_name.name, namelen);
+                *--end = '/';
+                retval = end;
                 dentry = parent;
         }
-        /* Get '/' right */
-        if (*buffer != '/')
-                *--buffer = '/';
 
-out:
-        spin_unlock(&dcache_lock);
-        return buffer;
+        return retval;
 
 global_root:
-        /*
-         * We went past the (vfsmount, dentry) we were looking for and have
-         * either hit a root dentry, a lazily unmounted dentry, an
-         * unconnected dentry, or the file is on a pseudo filesystem.
-         */
         namelen = dentry->d_name.len;
-        is_slash = (namelen == 1 && *dentry->d_name.name == '/');
-        if (is_slash || (dentry->d_sb->s_flags & MS_NOUSER)) {
-                /*
-                 * Make sure we won't return a pathname starting with '/'.
-                 *
-                 * Historically, we also glue together the root dentry and
-                 * remaining name for pseudo filesystems like pipefs, which
-                 * have the MS_NOUSER flag set. This results in pathnames
-                 * like "pipe:[439336]".
-                 */
-                if (*buffer == '/') {
-                        buffer++;
-                        buflen++;
-                }
-                if (is_slash)
-                        goto out;
-        }
-        if (buflen < namelen)
+        buflen -= namelen;
+        if (buflen < 0)
                 goto Elong;
-        buffer -= namelen;
-        memcpy(buffer, dentry->d_name.name, namelen);
-        goto out;
-
+        retval -= namelen-1;    /* hit the slash */
+        memcpy(retval, dentry->d_name.name, namelen);
+        return retval;
 Elong:
-        buffer = ERR_PTR(-ENAMETOOLONG);
-        goto out;
+        return ERR_PTR(-ENAMETOOLONG);
 }
 
 /* write full pathname into buffer and return start of pathname */
-char *d_path(struct dentry *dentry, struct vfsmount *vfsmnt, char *buf,
-             int buflen)
+char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
+                                char *buf, int buflen)
 {
         char *res;
         struct vfsmount *rootmnt;
@@ -1850,7 +1827,9 @@ char *d_path(struct dentry *dentry, struct vfsmount *vfsmnt, char *buf,
         rootmnt = mntget(current->fs->rootmnt);
         root = dget(current->fs->root);
         read_unlock(&current->fs->lock);
-        res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen, 0);
+        spin_lock(&dcache_lock);
+        res = __d_path(dentry, vfsmnt, root, rootmnt, buf, buflen);
+        spin_unlock(&dcache_lock);
         dput(root);
         mntput(rootmnt);
         return res;
@@ -1876,10 +1855,10 @@ char *d_path(struct dentry *dentry, struct vfsmount *vfsmnt, char *buf,
  */
 asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
 {
-        int error, len;
+        int error;
         struct vfsmount *pwdmnt, *rootmnt;
         struct dentry *pwd, *root;
-        char *page = (char *) __get_free_page(GFP_USER), *cwd;
+        char *page = (char *) __get_free_page(GFP_USER);
 
         if (!page)
                 return -ENOMEM;
@@ -1891,18 +1870,29 @@ asmlinkage long sys_getcwd(char __user *buf, unsigned long size)
         root = dget(current->fs->root);
         read_unlock(&current->fs->lock);
 
-        cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE, 1);
-        error = PTR_ERR(cwd);
-        if (IS_ERR(cwd))
-                goto out;
+        error = -ENOENT;
+        /* Has the current directory has been unlinked? */
+        spin_lock(&dcache_lock);
+        if (pwd->d_parent == pwd || !d_unhashed(pwd)) {
+                unsigned long len;
+                char * cwd;
 
-        error = -ERANGE;
-        len = PAGE_SIZE + page - cwd;
-        if (len <= size) {
-                error = len;
-                if (copy_to_user(buf, cwd, len))
-                        error = -EFAULT;
-        }
+                cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
+                spin_unlock(&dcache_lock);
+
+                error = PTR_ERR(cwd);
+                if (IS_ERR(cwd))
+                        goto out;
+
+                error = -ERANGE;
+                len = PAGE_SIZE + page - cwd;
+                if (len <= size) {
+                        error = len;
+                        if (copy_to_user(buf, cwd, len))
+                                error = -EFAULT;
+                }
+        } else
+                spin_unlock(&dcache_lock);
 
 out:
         dput(pwd);