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    SubjectRe: [PATCH 07/38] whiteout: Set S_OPAQUE inode flag when creating directories
    On Tue, Jun 15, 2010 at 11:39:37AM -0700, Valerie Aurora wrote:
    > From: Jan Blunck <jblunck@suse.de>
    >
    > In case of an union directory we don't want that the directories on lower
    > layers of the union "show through". So to prevent that the contents of
    > underlying directories magically shows up after a mkdir() we set the S_OPAQUE
    > flag if directories are created where a whiteout existed before.

    I found this hard to understand.

    Do you mean:

    For directories within a union that are whiteouts we don't want the entries of
    lower layer file system to "show through". To achieve this we set the S_OPAQUE
    flag after a mkdir() on directories that are whiteouts.

    >
    > Signed-off-by: Jan Blunck <jblunck@suse.de>
    > Signed-off-by: Valerie Aurora <vaurora@redhat.com>
    > ---
    > fs/namei.c | 11 ++++++++++-
    > include/linux/fs.h | 3 +++
    > 2 files changed, 13 insertions(+), 1 deletions(-)
    >
    > diff --git a/fs/namei.c b/fs/namei.c
    > index 2c723e2..8c67636 100644
    > --- a/fs/namei.c
    > +++ b/fs/namei.c
    > @@ -2107,6 +2107,7 @@ 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;
    > @@ -2119,9 +2120,17 @@ 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 7afdbd4..e9aa650 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
    > @@ -271,6 +272,8 @@ struct inodes_stat_t {
    > #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. */
    >
    > --
    > 1.6.3.3
    >
    > --
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