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Subject[PATCH 07/39] whiteout: Set opaque flag if new directory was previously a whiteout
Date
From: Jan Blunck <jblunck@suse.de>

If we mkdir() a directory on the top layer of a union, we don't want
entries from a matching directory on the lower layer to "show through"
suddenly. To prevent this, we set the opaque flag on a directory if
there was previously a white-out with the same name. (If there is no
white-out and the directory exists in a lower layer, then mkdir() will
fail with EEXIST.)

Signed-off-by: Jan Blunck <jblunck@suse.de>
Signed-off-by: Valerie Aurora <vaurora@redhat.com>
---
fs/namei.c | 11 ++++++++++-
include/linux/fs.h | 5 +++++
2 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 665d394..cd8b0d0 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2108,6 +2108,7 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
int error = may_create(dir, dentry);
+ int opaque = 0;

if (error)
return error;
@@ -2120,9 +2121,17 @@ int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
if (error)
return error;

+ if (d_is_whiteout(dentry))
+ opaque = 1;
+
error = dir->i_op->mkdir(dir, dentry, mode);
- if (!error)
+ if (!error) {
fsnotify_mkdir(dir, dentry);
+ if (opaque) {
+ dentry->d_inode->i_flags |= S_OPAQUE;
+ mark_inode_dirty(dentry->d_inode);
+ }
+ }
return error;
}

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1f80897..1dbe156 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -236,6 +236,7 @@ struct inodes_stat_t {
#define S_NOCMTIME 128 /* Do not update file c/mtime */
#define S_SWAPFILE 256 /* Do not truncate: swapon got its bmaps */
#define S_PRIVATE 512 /* Inode is fs-internal */
+#define S_OPAQUE 1024 /* Directory is opaque */

/*
* Note that nosuid etc flags are inode-specific: setting some file-system
@@ -270,6 +271,7 @@ struct inodes_stat_t {
#define IS_NOCMTIME(inode) ((inode)->i_flags & S_NOCMTIME)
#define IS_SWAPFILE(inode) ((inode)->i_flags & S_SWAPFILE)
#define IS_PRIVATE(inode) ((inode)->i_flags & S_PRIVATE)
+#define IS_OPAQUE(inode) ((inode)->i_flags & S_OPAQUE)

/* the read-only stuff doesn't really belong here, but any other place is
probably as bad and I don't want to create yet another include file. */
@@ -351,8 +353,11 @@ struct inodes_stat_t {
#define FS_NOTAIL_FL 0x00008000 /* file tail should not be merged */
#define FS_DIRSYNC_FL 0x00010000 /* dirsync behaviour (directories only) */
#define FS_TOPDIR_FL 0x00020000 /* Top of directory hierarchies*/
+/* 0x00040000 is used by ext4 */
#define FS_EXTENT_FL 0x00080000 /* Extents */
#define FS_DIRECTIO_FL 0x00100000 /* Use direct i/o */
+/* 0x00200000 and 0x00400000 also used by ext4 */
+#define FS_OPAQUE_FL 0x00800000 /* Dir is opaque */
#define FS_RESERVED_FL 0x80000000 /* reserved for ext2 lib */

#define FS_FL_USER_VISIBLE 0x0003DFFF /* User visible flags */
--
1.6.3.3


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