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    SubjectRe: [PATCH 11/38] whiteout: ext2 whiteout support
    On Tue, Jun 15, 2010 at 11:39:41AM -0700, Valerie Aurora wrote:
    > 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;
    > + }

    This looks odd, can someone tell me what's actually going with de and de1
    here please?

    > + 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 0b038e4..44d190c 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 fc13cc1..5ad2cbb 100644
    > --- a/fs/ext2/inode.c
    > +++ b/fs/ext2/inode.c
    > @@ -1184,7 +1184,8 @@ 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)
    > @@ -1195,6 +1196,8 @@ 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 */
    > @@ -1202,8 +1205,8 @@ 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)
    > @@ -1214,6 +1217,8 @@ 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 71efb0e..12195a5 100644
    > --- a/fs/ext2/namei.c
    > +++ b/fs/ext2/namei.c
    > @@ -55,15 +55,16 @@ 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);
    > @@ -242,6 +243,10 @@ 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);
    > @@ -307,6 +312,61 @@ 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;
    > + }
    > +
    > + dquot_initialize(dir);
    > +
    > + 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);
    > + }

    Is page "always" set in ext2_find_entry(), I couldn't quite make that out?
    If dentry is negative, isn't this a use without initialization of page in
    ext2_whiteout_entry().

    > +
    > + 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 )
    > {
    > @@ -409,6 +469,7 @@ 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 42e4a30..000ee17 100644
    > --- a/fs/ext2/super.c
    > +++ b/fs/ext2/super.c
    > @@ -1079,6 +1079,12 @@ 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_msg(sb, KERN_WARNING,
    > "warning: 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 2dfa707..20468bd 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 = 5,
    > EXT2_FT_SOCK = 6,
    > EXT2_FT_SYMLINK = 7,
    > + EXT2_FT_WHT = 8,
    > EXT2_FT_MAX
    > };
    >
    > --
    > 1.6.3.3
    >
    > --
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