From: Jan Blunck <jblunck@xxxxxxx>
do_whiteout() allows removal of a directory when it has whiteouts but
is logically empty.
XXX - This patch abuses readdir() to check if the union directory is
logically empty - that is, all the entries are whiteouts (or "." or
".."). Currently, we have no clean VFS interface to ask the lower
file system if a directory is empty.
Fixes:
- Add ->is_directory_empty() op
- Add is_directory_empty flag to dentry (ugly dcache populate)
- Ask underlying fs to remove it and look for an error return
- (your idea here)
Signed-off-by: Jan Blunck <jblunck@xxxxxxx>
Signed-off-by: Valerie Aurora <vaurora@xxxxxxxxxx>
---
fs/namei.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 90 insertions(+), 0 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 99ca663..0014052 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -32,6 +32,7 @@
#include <linux/fcntl.h>
#include <linux/device_cgroup.h>
#include <linux/fs_struct.h>
+#include <linux/init_task.h>
#include <asm/uaccess.h>
#include "internal.h"
@@ -2645,6 +2646,95 @@ error_unlock:
* dentry, and if that is true (possibly after pruning the dcache),
* then we drop the dentry now.
*
+ * XXX - We are abusing readdir to check if a union directory is
+ * logically empty.
+ */
+static int filldir_is_empty(void *__buf, const char *name, int namelen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ int *is_empty = __buf;
+
+ switch (namelen) {
+ case 2:
+ if (name[1] != '.')
+ break;
+ case 1:
+ if (name[0] != '.')
+ break;
+ return 0;
+ }
+
+ if (d_type == DT_WHT)
+ return 0;
+
+ *is_empty = 0;
+ return 1; /* no point scanning further */
+}
+
+static int directory_is_empty(struct path *path)
+{
+ struct file *file;
+ int err;
+ int is_empty = 1;
+
+ BUG_ON(!S_ISDIR(path->dentry->d_inode->i_mode));
+
+ /* references for the file pointer */
+ path_get(path);
+
+ file = dentry_open(path->dentry, path->mnt, O_RDONLY, &init_cred);
+ if (IS_ERR(file))
+ return 0;
+
+ err = vfs_readdir(file, filldir_is_empty, &is_empty);
+
+ fput(file);
+ return is_empty;
+}
+
+static int do_whiteout(struct nameidata *nd, struct path *path, int isdir)
+{
+ struct path safe = nd->path;
+ struct dentry *dentry = path->dentry;
+ int err;
+
+ path_get(&safe);
+
+ err = may_delete(nd->path.dentry->d_inode, dentry, isdir);
+ if (err)
+ goto out;
+
+ err = -ENOTEMPTY;
+ if (isdir && !directory_is_empty(path))
+ goto out;
+
+ if (nd->path.dentry != dentry->d_parent) {
+ dentry = __lookup_hash(&path->dentry->d_name, nd->path.dentry,
+ nd);
+ err = PTR_ERR(dentry);
+ if (IS_ERR(dentry))
+ goto out;
+
+ dput(path->dentry);
+ if (path->mnt != safe.mnt)
+ mntput(path->mnt);
+ path->mnt = nd->path.mnt;
+ path->dentry = dentry;
+ }
+
+ err = vfs_whiteout(nd->path.dentry->d_inode, dentry, isdir);
+
+out:
+ path_put(&safe);
+ return err;
+}
+
+/*
+ * We try to drop the dentry early: we should have
+ * a usage count of 2 if we're the only user of this
+ * dentry, and if that is true (possibly after pruning
+ * the dcache), then we drop the dentry now.
+ *
* A low-level filesystem can, if it choses, legally
* do a
*
--
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