[PATCH 15/41] whiteout: ext2 whiteout support

From: Valerie Aurora
Date: Wed Oct 21 2009 - 15:27:47 EST

From: Jan Blunck <jblunck@xxxxxxx>

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 - Whiteouts could be implemented as special symbolic links

Signed-off-by: Jan Blunck <jblunck@xxxxxxx>
Signed-off-by: Valerie Aurora <vaurora@xxxxxxxxxx>
Cc: Theodore Tso <tytso@xxxxxxx>
Cc: linux-ext4@xxxxxxxxxxxxxxx
---
fs/ext2/dir.c | 96 +++++++++++++++++++++++++++++++++++++++++++++--
fs/ext2/ext2.h | 3 +
fs/ext2/inode.c | 11 ++++-
fs/ext2/namei.c | 65 ++++++++++++++++++++++++++++++-
fs/ext2/super.c | 7 +++
include/linux/ext2_fs.h | 4 ++
6 files changed, 176 insertions(+), 10 deletions(-)

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index cb8ceff..d4628c0 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;
+ }
+ de->name_len = namelen;
+ memcpy(de->name, name, namelen);
+ de->inode = 0;
+ de->file_type = EXT2_FT_WHT;
+ err = ext2_commit_chunk(page, pos, rec_len);
+ dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
+ EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
+ mark_inode_dirty(dir);
+ /* OFFSET_CACHE */
+out_put:
+ ext2_put_page(page);
+ return err;
+out_unlock:
+ unlock_page(page);
+ goto out_put;
+}
+
/*
* Set the first fragment of directory.
*/
diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 9a8a8e2..a7f057f 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -102,9 +102,12 @@ extern void ext2_rsv_window_add(struct super_block *sb, struct ext2_reserve_wind
/* dir.c */
extern int ext2_add_link (struct dentry *, struct inode *);
extern ino_t ext2_inode_by_name(struct inode *, struct qstr *);
+extern ino_t ext2_inode_by_dentry(struct inode *, struct dentry *);
extern int ext2_make_empty(struct inode *, struct inode *);
extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,struct qstr *, struct page **);
extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
+extern int ext2_whiteout_entry (struct inode *, struct dentry *,
+ struct ext2_dir_entry_2 *, struct page *);
extern int ext2_empty_dir (struct inode *);
extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int);
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index e271303..5f76e44 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -1176,7 +1176,8 @@ void ext2_set_inode_flags(struct inode *inode)
{
unsigned int flags = EXT2_I(inode)->i_flags;

- inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
+ inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|
+ S_OPAQUE);
if (flags & EXT2_SYNC_FL)
inode->i_flags |= S_SYNC;
if (flags & EXT2_APPEND_FL)
@@ -1187,6 +1188,8 @@ void ext2_set_inode_flags(struct inode *inode)
inode->i_flags |= S_NOATIME;
if (flags & EXT2_DIRSYNC_FL)
inode->i_flags |= S_DIRSYNC;
+ if (flags & EXT2_OPAQUE_FL)
+ inode->i_flags |= S_OPAQUE;
}

/* Propagate flags from i_flags to EXT2_I(inode)->i_flags */
@@ -1194,8 +1197,8 @@ void ext2_get_inode_flags(struct ext2_inode_info *ei)
{
unsigned int flags = ei->vfs_inode.i_flags;

- ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|
- EXT2_IMMUTABLE_FL|EXT2_NOATIME_FL|EXT2_DIRSYNC_FL);
+ ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|EXT2_IMMUTABLE_FL|
+ EXT2_NOATIME_FL|EXT2_DIRSYNC_FL|EXT2_OPAQUE_FL);
if (flags & S_SYNC)
ei->i_flags |= EXT2_SYNC_FL;
if (flags & S_APPEND)
@@ -1206,6 +1209,8 @@ void ext2_get_inode_flags(struct ext2_inode_info *ei)
ei->i_flags |= EXT2_NOATIME_FL;
if (flags & S_DIRSYNC)
ei->i_flags |= EXT2_DIRSYNC_FL;
+ if (flags & S_OPAQUE)
+ ei->i_flags |= EXT2_OPAQUE_FL;
}

struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 78d9b92..9c4eef2 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -54,15 +54,16 @@ static inline int ext2_add_nondir(struct dentry *dentry, struct inode *inode)
* Methods themselves.
*/

-static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, struct nameidata *nd)
+static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry,
+ struct nameidata *nd)
{
struct inode * inode;
ino_t ino;
-
+
if (dentry->d_name.len > EXT2_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);

- ino = ext2_inode_by_name(dir, &dentry->d_name);
+ ino = ext2_inode_by_dentry(dir, dentry);
inode = NULL;
if (ino) {
inode = ext2_iget(dir->i_sb, ino);
@@ -230,6 +231,10 @@ static int ext2_mkdir(struct inode * dir, struct dentry * dentry, int mode)
else
inode->i_mapping->a_ops = &ext2_aops;

+ /* if we call mkdir on a whiteout create an opaque directory */
+ if (dentry->d_flags & DCACHE_WHITEOUT)
+ inode->i_flags |= S_OPAQUE;
+
inode_inc_link_count(inode);

err = ext2_make_empty(inode, dir);
@@ -293,6 +298,59 @@ static int ext2_rmdir (struct inode * dir, struct dentry *dentry)
return err;
}

+/*
+ * Create a whiteout for the dentry
+ */
+static int ext2_whiteout(struct inode *dir, struct dentry *dentry,
+ struct dentry *new_dentry)
+{
+ struct inode * inode = dentry->d_inode;
+ struct ext2_dir_entry_2 * de = NULL;
+ struct page * page;
+ int err = -ENOTEMPTY;
+
+ if (!EXT2_HAS_INCOMPAT_FEATURE(dir->i_sb,
+ EXT2_FEATURE_INCOMPAT_FILETYPE)) {
+ ext2_error (dir->i_sb, "ext2_whiteout",
+ "can't set whiteout filetype");
+ err = -EPERM;
+ goto out;
+ }
+
+ if (inode) {
+ if (S_ISDIR(inode->i_mode) && !ext2_empty_dir(inode))
+ goto out;
+
+ err = -ENOENT;
+ de = ext2_find_entry (dir, &dentry->d_name, &page);
+ if (!de)
+ goto out;
+ lock_page(page);
+ }
+
+ err = ext2_whiteout_entry (dir, dentry, de, page);
+ if (err)
+ goto out;
+
+ spin_lock(&new_dentry->d_lock);
+ new_dentry->d_flags |= DCACHE_WHITEOUT;
+ spin_unlock(&new_dentry->d_lock);
+ d_add(new_dentry, NULL);
+
+ if (inode) {
+ inode->i_ctime = dir->i_ctime;
+ inode_dec_link_count(inode);
+ if (S_ISDIR(inode->i_mode)) {
+ inode->i_size = 0;
+ inode_dec_link_count(inode);
+ inode_dec_link_count(dir);
+ }
+ }
+ err = 0;
+out:
+ return err;
+}
+
static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
struct inode * new_dir, struct dentry * new_dentry )
{
@@ -392,6 +450,7 @@ const struct inode_operations ext2_dir_inode_operations = {
.mkdir = ext2_mkdir,
.rmdir = ext2_rmdir,
.mknod = ext2_mknod,
+ .whiteout = ext2_whiteout,
.rename = ext2_rename,
#ifdef CONFIG_EXT2_FS_XATTR
.setxattr = generic_setxattr,
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 1a9ffee..c414c6d 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1062,6 +1062,13 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL))
ext2_warning(sb, __func__,
"mounting ext3 filesystem as ext2");
+
+ /*
+ * Whiteouts (and fallthrus) require explicit whiteout support.
+ */
+ if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_WHITEOUT))
+ sb->s_flags |= MS_WHITEOUT;
+
ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY);
return 0;

diff --git a/include/linux/ext2_fs.h b/include/linux/ext2_fs.h
index 121720d..bd10826 100644
--- a/include/linux/ext2_fs.h
+++ b/include/linux/ext2_fs.h
@@ -189,6 +189,7 @@ struct ext2_group_desc
#define EXT2_NOTAIL_FL FS_NOTAIL_FL /* file tail should not be merged */
#define EXT2_DIRSYNC_FL FS_DIRSYNC_FL /* dirsync behaviour (directories only) */
#define EXT2_TOPDIR_FL FS_TOPDIR_FL /* Top of directory hierarchies*/
+#define EXT2_OPAQUE_FL 0x00040000
#define EXT2_RESERVED_FL FS_RESERVED_FL /* reserved for ext2 lib */

#define EXT2_FL_USER_VISIBLE FS_FL_USER_VISIBLE /* User visible flags */
@@ -503,10 +504,12 @@ struct ext2_super_block {
#define EXT3_FEATURE_INCOMPAT_RECOVER 0x0004
#define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV 0x0008
#define EXT2_FEATURE_INCOMPAT_META_BG 0x0010
+#define EXT2_FEATURE_INCOMPAT_WHITEOUT 0x0020
#define EXT2_FEATURE_INCOMPAT_ANY 0xffffffff

#define EXT2_FEATURE_COMPAT_SUPP EXT2_FEATURE_COMPAT_EXT_ATTR
#define EXT2_FEATURE_INCOMPAT_SUPP (EXT2_FEATURE_INCOMPAT_FILETYPE| \
+ EXT2_FEATURE_INCOMPAT_WHITEOUT| \
EXT2_FEATURE_INCOMPAT_META_BG)
#define EXT2_FEATURE_RO_COMPAT_SUPP (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \
EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \
@@ -573,6 +576,7 @@ enum {
EXT2_FT_FIFO,
EXT2_FT_SOCK,
EXT2_FT_SYMLINK,
+ EXT2_FT_WHT,
EXT2_FT_MAX
};

--
1.6.3.3

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