> From: Jan Blunck <jblunck@suse.de>
>
> This patch adds whiteout support to EXT2. A whiteout is an empty directory
> entry (inode == 0) with the file type set to EXT2_FT_WHT. Therefore it
> allocates space in directories. Due to being implemented as a filetype it is
> necessary to have the EXT2_FEATURE_INCOMPAT_FILETYPE flag set.
>
> XXX - Needs serious review. Al wonders: What happens with a delete at
> the beginning of a block? Will we find the matching dentry or the
> first empty space?
>
> Signed-off-by: Jan Blunck <jblunck@suse.de>
> Signed-off-by: Valerie Aurora <vaurora@redhat.com>
> Cc: Theodore Tso <tytso@mit.edu>
> Cc:
linux-ext4@vger.kernel.org
> ---
> fs/ext2/dir.c | 96 +++++++++++++++++++++++++++++++++++++++++++++--
> fs/ext2/ext2.h | 3 +
> fs/ext2/inode.c | 11 ++++-
> fs/ext2/namei.c | 67 +++++++++++++++++++++++++++++++-
> fs/ext2/super.c | 6 +++
> include/linux/ext2_fs.h | 4 ++
> 6 files changed, 177 insertions(+), 10 deletions(-)
>
> diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> index 57207a9..030bd46 100644
> --- a/fs/ext2/dir.c
> +++ b/fs/ext2/dir.c
> @@ -219,7 +219,7 @@ static inline int ext2_match (int len, const char * const name,
> {
> if (len != de->name_len)
> return 0;
> - if (!de->inode)
> + if (!de->inode && (de->file_type != EXT2_FT_WHT))
> return 0;
> return !memcmp(name, de->name, len);
> }
> @@ -255,6 +255,7 @@ static unsigned char ext2_filetype_table[EXT2_FT_MAX] = {
> [EXT2_FT_FIFO] = DT_FIFO,
> [EXT2_FT_SOCK] = DT_SOCK,
> [EXT2_FT_SYMLINK] = DT_LNK,
> + [EXT2_FT_WHT] = DT_WHT,
> };
>
> #define S_SHIFT 12
> @@ -448,6 +449,26 @@ ino_t ext2_inode_by_name(struct inode *dir, struct qstr *child)
> return res;
> }
>
> +/* Special version for filetype based whiteout support */
> +ino_t ext2_inode_by_dentry(struct inode *dir, struct dentry *dentry)
> +{
> + ino_t res = 0;
> + struct ext2_dir_entry_2 *de;
> + struct page *page;
> +
> + de = ext2_find_entry (dir, &dentry->d_name, &page);
> + if (de) {
> + res = le32_to_cpu(de->inode);
> + if (!res && de->file_type == EXT2_FT_WHT) {
> + spin_lock(&dentry->d_lock);
> + dentry->d_flags |= DCACHE_WHITEOUT;
> + spin_unlock(&dentry->d_lock);
> + }
> + ext2_put_page(page);
> + }
> + return res;
> +}
> +
> /* Releases the page */
> void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
> struct page *page, struct inode *inode, int update_times)
> @@ -523,7 +544,8 @@ static ext2_dirent * ext2_append_entry(struct dentry * dentry,
> goto got_it;
> name_len = EXT2_DIR_REC_LEN(de->name_len);
> rec_len = ext2_rec_len_from_disk(de->rec_len);
> - if (!de->inode && rec_len >= reclen)
> + if (!de->inode && (de->file_type != EXT2_FT_WHT) &&
> + (rec_len >= reclen))
> goto got_it;
> if (rec_len >= name_len + reclen)
> goto got_it;
> @@ -564,8 +586,11 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
> return PTR_ERR(de);
>
> err = -EEXIST;
> - if (ext2_match (namelen, name, de))
> + if (ext2_match (namelen, name, de)) {
> + if (de->file_type == EXT2_FT_WHT)
> + goto got_it;
> goto out_unlock;
> + }
>
> got_it:
> name_len = EXT2_DIR_REC_LEN(de->name_len);
> @@ -577,7 +602,8 @@ got_it:
> &page, NULL);
> if (err)
> goto out_unlock;
> - if (de->inode) {
> + if (de->inode || ((de->file_type == EXT2_FT_WHT) &&
> + !ext2_match (namelen, name, de))) {
> ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
> de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
> de->rec_len = ext2_rec_len_to_disk(name_len);
> @@ -646,6 +672,68 @@ out:
> return err;
> }
>
> +int ext2_whiteout_entry (struct inode * dir, struct dentry * dentry,
> + struct ext2_dir_entry_2 * de, struct page * page)
> +{
> + const char *name = dentry->d_name.name;
> + int namelen = dentry->d_name.len;
> + unsigned short rec_len, name_len;
> + loff_t pos;
> + int err;
> +
> + if (!de) {
> + de = ext2_append_entry(dentry, &page);
> + BUG_ON(!de);
> + }
> +
> + err = -EEXIST;
> + if (ext2_match (namelen, name, de) &&
> + (de->file_type == EXT2_FT_WHT)) {
> + ext2_error(dir->i_sb, __func__,
> + "entry is already a whiteout in directory #%lu",
> + dir->i_ino);
> + goto out_unlock;
> + }
> +
> + name_len = EXT2_DIR_REC_LEN(de->name_len);
> + rec_len = ext2_rec_len_from_disk(de->rec_len);
> +
> + pos = page_offset(page) +
> + (char*)de - (char*)page_address(page);
> + err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
> + &page, NULL);
> + if (err)
> + goto out_unlock;
> + /*
> + * We whiteout an existing entry. Do what ext2_delete_entry() would do,
> + * except that we don't need to merge with the previous entry since
> + * we are going to reuse it.
> + */
> + if (ext2_match (namelen, name, de))
> + de->inode = 0;
> + if (de->inode || (de->file_type == EXT2_FT_WHT)) {
> + ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
> + de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
> + de->rec_len = ext2_rec_len_to_disk(name_len);
> + de = de1;
> + }
