union mounts: fix various bugs related to handling of mountpoints and copyups

SVN-Revision: 17777

diff --git a/target/linux/generic-2.6/patches-2.6.31/235-union_mount_fixes.patch b/target/linux/generic-2.6/patches-2.6.31/235-union_mount_fixes.patch
new file mode 100644 (file)
index 0000000..cea1351
--- /dev/null
+++ b/target/linux/generic-2.6/patches-2.6.31/235-union_mount_fixes.patch
@@ -0,0 +1,117 @@
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -1656,8 +1656,10 @@ static int do_move_mount(struct path *pa
+ 
+       /* moving to or from a union mount is not supported */
+       err = -EINVAL;
++#if 0
+       if (IS_MNT_UNION(path->mnt))
+               goto exit;
++#endif
+       if (IS_MNT_UNION(old_path.mnt))
+               goto exit;
+ 
+--- a/fs/union.c
++++ b/fs/union.c
+@@ -260,8 +260,6 @@ int append_to_union(struct vfsmount *mnt
+       spin_lock(&union_lock);
+       um = union_lookup(dentry, mnt);
+       if (um) {
+-              BUG_ON((um->u_next.dentry != dest_dentry) ||
+-                     (um->u_next.mnt != dest_mnt));
+               spin_unlock(&union_lock);
+               union_put(this);
+               return 0;
+@@ -274,6 +272,23 @@ int append_to_union(struct vfsmount *mnt
+       return 0;
+ }
+ 
++int follow_union_mountpoint(struct path *path)
++{
++      struct path new_path = *path;
++
++      path_get(&new_path);
++      while (follow_union_down(&new_path)) {
++              if (new_path.dentry != new_path.mnt->mnt_root)
++                      continue;
++
++              path_put(path);
++              *path = new_path;
++              return 1;
++      }
++      path_put(&new_path);
++      return 0;
++}
++
+ /*
+  * follow_union_down - follow the union stack one layer down
+  *
+--- a/include/linux/union.h
++++ b/include/linux/union.h
+@@ -47,6 +47,7 @@ extern int append_to_union(struct vfsmou
+                          struct vfsmount *, struct dentry *);
+ extern int follow_union_down(struct path *);
+ extern int follow_union_mount(struct path *);
++extern int follow_union_mountpoint(struct path *path);
+ extern void __d_drop_unions(struct dentry *);
+ extern void shrink_d_unions(struct dentry *);
+ extern void __shrink_d_unions(struct dentry *, struct list_head *);
+@@ -68,6 +69,7 @@ extern int union_permission(struct path 
+ #define append_to_union(x1, y1, x2, y2)       ({ BUG(); (0); })
+ #define follow_union_down(x)          ({ (0); })
+ #define follow_union_mount(x) ({ (0); })
++#define follow_union_mountpoint(x)    ({ (0); })
+ #define __d_drop_unions(x)            do { } while (0)
+ #define shrink_d_unions(x)            do { } while (0)
+ #define __shrink_d_unions(x,y)                do { } while (0)
+--- a/fs/namei.c
++++ b/fs/namei.c
+@@ -613,6 +613,9 @@ static int cache_lookup_union(struct nam
+                   !S_ISDIR(path->dentry->d_inode->i_mode))
+                       goto out;
+ 
++              if (follow_union_mountpoint(path))
++                      goto out;
++
+               /* Build the union stack for this part */
+               res = __cache_lookup_build_union(nd, name, path);
+               if (res) {
+@@ -886,6 +889,9 @@ static int real_lookup_union(struct name
+           !S_ISDIR(path->dentry->d_inode->i_mode))
+               goto out;
+ 
++      if (follow_union_mountpoint(path))
++              goto out;
++
+       /* Build the union stack for this part */
+       res = __real_lookup_build_union(nd, name, path);
+       if (res) {
+@@ -1813,6 +1819,9 @@ int hash_lookup_union(struct nameidata *
+           !S_ISDIR(path->dentry->d_inode->i_mode))
+               goto out;
+ 
++      if (follow_union_mountpoint(path))
++              goto out;
++
+       /* Build the union stack for this part */
+       res = __hash_lookup_build_union(nd, name, path);
+       if (res) {
+--- a/fs/readdir.c
++++ b/fs/readdir.c
+@@ -17,6 +17,7 @@
+ #include <linux/syscalls.h>
+ #include <linux/unistd.h>
+ #include <linux/union.h>
++#include <linux/mount.h>
+ 
+ #include <asm/uaccess.h>
+ 
+@@ -45,7 +46,7 @@ int vfs_readdir(struct file *file, filld
+                * below this one in the union stack.
+                */
+               if (is_unionized(file->f_path.dentry, file->f_path.mnt) &&
+-                  !IS_OPAQUE(inode)) {
++                  !IS_OPAQUE(inode) && IS_MNT_UNION(file->f_path.mnt)) {
+                       res = union_copyup_dir(&file->f_path);
+                       if (res)
+                               goto out_unlock;