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Subject[PATCH 08/39] whiteout: Allow removal of a directory with whiteouts
Date
From: Jan Blunck <jblunck@suse.de>

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@suse.de>
Signed-off-by: Valerie Aurora <vaurora@redhat.com>
---
fs/namei.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 84 insertions(+), 0 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index cd8b0d0..0b6378e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2250,6 +2250,90 @@ static int vfs_whiteout(struct inode *dir, struct dentry *old_dentry, int isdir)
}

/*
+ * 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 namlen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ int *is_empty = (int *)__buf;
+
+ switch (namlen) {
+ 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 0;
+}
+
+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, current_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
--
1.6.3.3


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