Re: [PATCH 11/38] whiteout: ext2 whiteout support

From: Ian Kent
Date: Tue Jul 13 2010 - 00:24:36 EST

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On Tue, Jun 15, 2010 at 11:39:41AM -0700, Valerie Aurora wrote:
> 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 - 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@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 | 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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Next message: KAMEZAWA Hiroyuki: "Re: [RFC] Tight check of pfn_valid on sparsemem"
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