Date:   Mon, 22 May 2017 13:30:23 +0900
From:   Hyunchul Lee <hyc.lee@...il.com>
To:     Richard Weinberger <richard@....at>
CC:     <linux-mtd@...ts.infradead.org>, <david@...ma-star.at>,
        <bfields@...hat.com>, <dedekind1@...il.com>,
        <linux-kernel@...r.kernel.org>, <adrian.hunter@...el.com>,
        <leon.pollak@...il.com>, <adilger.kernel@...ger.ca>,
        <linux-fsdevel@...r.kernel.org>, <marcus.folkesson@...il.com>,
        <akpm@...ux-foundation.org>, <rockdotlee@...il.com>,
        <kernel-team@....com>
Subject: Re: [PATCH 4/6] ubifs: Maintain a parent pointer

Hi Richard,

On Sun, May 21, 2017 at 10:20:49PM +0200, Richard Weinberger wrote:
> The new feature UBIFS_FLG_PARENTPOINTER allows looking
> up the parent. Usually the Linux VFS walks down the filesystem
> and no parent pointers are needed. But when a filesystem
> is exportable via NFS such a lookup is needed.
> We can use a padding field in struct ubifs_ino_node to
> maintain a pointer to the parent inode.
> 
> Signed-off-by: Richard Weinberger <richard@....at>
> ---
>  fs/ubifs/dir.c         | 21 +++++++++++++++++++--
>  fs/ubifs/journal.c     |  5 ++++-
>  fs/ubifs/sb.c          |  2 ++
>  fs/ubifs/super.c       |  1 +
>  fs/ubifs/ubifs-media.h | 12 +++++++++---
>  fs/ubifs/ubifs.h       |  4 ++++
>  6 files changed, 39 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> index e79b529df9c3..a6eadb52a1a8 100644
> --- a/fs/ubifs/dir.c
> +++ b/fs/ubifs/dir.c
> @@ -171,6 +171,7 @@ struct inode *ubifs_new_inode(struct ubifs_info *c, struct inode *dir,
>  	}
>  
>  	inode->i_ino = ++c->highest_inum;
> +	ui->parent_inum = dir->i_ino;
>  	/*
>  	 * The creation sequence number remains with this inode for its
>  	 * lifetime. All nodes for this inode have a greater sequence number,
> @@ -1374,7 +1375,7 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,
>  	if (unlink)
>  		ubifs_assert(inode_is_locked(new_inode));
>  
> -	if (old_dir != new_dir) {
> +	if (move) {
>  		if (ubifs_crypt_is_encrypted(new_dir) &&
>  		    !fscrypt_has_permitted_context(new_dir, old_inode))
>  			return -EPERM;
> @@ -1528,8 +1529,12 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,
>  		mark_inode_dirty(whiteout);
>  		whiteout->i_state &= ~I_LINKABLE;
>  		iput(whiteout);
> +		whiteout_ui->parent_inum = new_dir->i_ino;
>  	}
>  
> +	if (move)
> +		old_inode_ui->parent_inum = new_dir->i_ino;
> +
>  	err = ubifs_jnl_rename(c, old_dir, old_inode, &old_nm, new_dir,
>  			       new_inode, &new_nm, whiteout, sync);

I think that old_inode_ui->parent_inum could point old_dir, even though old_inode
is a child of new_dir. this could happen that there is power-cut before
old_inode is synced. so I guess that old_inode is needed to be written with
rename's node group in ubifs_jnl_rename. is it right?

>  	if (err)
> @@ -1571,6 +1576,8 @@ static int do_rename(struct inode *old_dir, struct dentry *old_dentry,
>  				inc_nlink(old_dir);
>  		}
>  	}
> +	if (move)
> +		old_inode_ui->parent_inum = old_dir->i_ino;
>  	if (whiteout) {
>  		drop_nlink(whiteout);
>  		iput(whiteout);
> @@ -1592,6 +1599,8 @@ static int ubifs_xrename(struct inode *old_dir, struct dentry *old_dentry,
>  	int sync = IS_DIRSYNC(old_dir) || IS_DIRSYNC(new_dir);
>  	struct inode *fst_inode = d_inode(old_dentry);
>  	struct inode *snd_inode = d_inode(new_dentry);
> +	struct ubifs_inode *fst_inode_ui = ubifs_inode(fst_inode);
> +	struct ubifs_inode *snd_inode_ui = ubifs_inode(snd_inode);
>  	struct timespec time;
>  	int err;
>  	struct fscrypt_name fst_nm, snd_nm;
> @@ -1623,7 +1632,10 @@ static int ubifs_xrename(struct inode *old_dir, struct dentry *old_dentry,
>  	old_dir->i_mtime = old_dir->i_ctime = time;
>  	new_dir->i_mtime = new_dir->i_ctime = time;
>  
> -	if (old_dir != new_dir) {
> +	if (new_dir != old_dir) {
> +		fst_inode_ui->parent_inum = new_dir->i_ino;
> +		snd_inode_ui->parent_inum = old_dir->i_ino;
> +
>  		if (S_ISDIR(fst_inode->i_mode) && !S_ISDIR(snd_inode->i_mode)) {
>  			inc_nlink(new_dir);
>  			drop_nlink(old_dir);
> @@ -1637,6 +1649,11 @@ static int ubifs_xrename(struct inode *old_dir, struct dentry *old_dentry,
>  	err = ubifs_jnl_xrename(c, old_dir, fst_inode, &fst_nm, new_dir,
>  				snd_inode, &snd_nm, sync);
>  
> +	if (err && new_dir != old_dir) {
> +		fst_inode_ui->parent_inum = old_dir->i_ino;
> +		snd_inode_ui->parent_inum = new_dir->i_ino;
> +	}
> +
>  	unlock_4_inodes(old_dir, new_dir, NULL, NULL);
>  	ubifs_release_budget(c, &req);
>  
> diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
> index 294519b98874..8eaf8f2f1fe1 100644
> --- a/fs/ubifs/journal.c
> +++ b/fs/ubifs/journal.c
> @@ -66,7 +66,6 @@
>   */
>  static inline void zero_ino_node_unused(struct ubifs_ino_node *ino)
>  {
> -	memset(ino->padding1, 0, 4);
>  	memset(ino->padding2, 0, 26);
>  }
>  
> @@ -470,6 +469,10 @@ static void pack_inode(struct ubifs_info *c, struct ubifs_ino_node *ino,
>  	ino->xattr_cnt   = cpu_to_le32(ui->xattr_cnt);
>  	ino->xattr_size  = cpu_to_le32(ui->xattr_size);
>  	ino->xattr_names = cpu_to_le32(ui->xattr_names);
> +	if (c->parent_pointer)
> +		ino->parent_inum = cpu_to_le32(ui->parent_inum);
> +	else
> +		ino->parent_inum = 0;
>  	zero_ino_node_unused(ino);
>  
>  	/*
> diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
> index 8c25081a5109..f2097c47f629 100644
> --- a/fs/ubifs/sb.c
> +++ b/fs/ubifs/sb.c
> @@ -166,6 +166,7 @@ static int create_default_filesystem(struct ubifs_info *c)
>  	if (big_lpt)
>  		sup_flags |= UBIFS_FLG_BIGLPT;
>  	sup_flags |= UBIFS_FLG_DOUBLE_HASH;
> +	sup_flags |= UBIFS_FLG_PARENTPOINTER;
>  
>  	sup->ch.node_type  = UBIFS_SB_NODE;
>  	sup->key_hash      = UBIFS_KEY_HASH_R5;
> @@ -639,6 +640,7 @@ int ubifs_read_superblock(struct ubifs_info *c)
>  	c->space_fixup = !!(sup_flags & UBIFS_FLG_SPACE_FIXUP);
>  	c->double_hash = !!(sup_flags & UBIFS_FLG_DOUBLE_HASH);
>  	c->encrypted = !!(sup_flags & UBIFS_FLG_ENCRYPTION);
> +	c->parent_pointer = !!(sup_flags & UBIFS_FLG_PARENTPOINTER);
>  
>  	if ((sup_flags & ~UBIFS_FLG_MASK) != 0) {
>  		ubifs_err(c, "Unknown feature flags found: %#x",
> diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
> index cf4cc99b75b5..7560071534bf 100644
> --- a/fs/ubifs/super.c
> +++ b/fs/ubifs/super.c
> @@ -154,6 +154,7 @@ struct inode *ubifs_iget(struct super_block *sb, unsigned long inum)
>  	ui->synced_i_size = ui->ui_size = inode->i_size;
>  
>  	ui->xattr = (ui->flags & UBIFS_XATTR_FL) ? 1 : 0;
> +	ui->parent_inum = le32_to_cpu(ino->parent_inum);
>  
>  	err = validate_inode(c, inode);
>  	if (err)
> diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
> index 5939776c7359..b3cb76cedf20 100644
> --- a/fs/ubifs/ubifs-media.h
> +++ b/fs/ubifs/ubifs-media.h
> @@ -427,15 +427,21 @@ enum {
>   * UBIFS_FLG_DOUBLE_HASH: store a 32bit cookie in directory entry nodes to
>   *			  support 64bit cookies for lookups by hash
>   * UBIFS_FLG_ENCRYPTION: this filesystem contains encrypted files
> + * UBIFS_FLG_PARENTPOINTER: inode nodes maintain a pointer to the parent dir
>   */
>  enum {
>  	UBIFS_FLG_BIGLPT = 0x02,
>  	UBIFS_FLG_SPACE_FIXUP = 0x04,
>  	UBIFS_FLG_DOUBLE_HASH = 0x08,
>  	UBIFS_FLG_ENCRYPTION = 0x10,
> +	UBIFS_FLG_PARENTPOINTER = 0x20,
>  };
>  
> -#define UBIFS_FLG_MASK (UBIFS_FLG_BIGLPT|UBIFS_FLG_SPACE_FIXUP|UBIFS_FLG_DOUBLE_HASH|UBIFS_FLG_ENCRYPTION)
> +#define UBIFS_FLG_MASK (UBIFS_FLG_BIGLPT		\
> +			|UBIFS_FLG_SPACE_FIXUP		\
> +			|UBIFS_FLG_DOUBLE_HASH		\
> +			|UBIFS_FLG_ENCRYPTION		\
> +			|UBIFS_FLG_PARENTPOINTER)
>  
>  /**
>   * struct ubifs_ch - common header node.
> @@ -494,7 +500,7 @@ union ubifs_dev_desc {
>   * @data_len: inode data length
>   * @xattr_cnt: count of extended attributes this inode has
>   * @xattr_size: summarized size of all extended attributes in bytes
> - * @padding1: reserved for future, zeroes
> + * @parent_inum: parent inode number
>   * @xattr_names: sum of lengths of all extended attribute names belonging to
>   *               this inode
>   * @compr_type: compression type used for this inode
> @@ -528,7 +534,7 @@ struct ubifs_ino_node {
>  	__le32 data_len;
>  	__le32 xattr_cnt;
>  	__le32 xattr_size;
> -	__u8 padding1[4]; /* Watch 'zero_ino_node_unused()' if changing! */
> +	__le32 parent_inum;
>  	__le32 xattr_names;
>  	__le16 compr_type;
>  	__u8 padding2[26]; /* Watch 'zero_ino_node_unused()' if changing! */
> diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
> index f14dcc890e47..3c64481f4032 100644
> --- a/fs/ubifs/ubifs.h
> +++ b/fs/ubifs/ubifs.h
> @@ -353,6 +353,7 @@ struct ubifs_gced_idx_leb {
>   *                 currently stored on the flash; used only for regular file
>   *                 inodes
>   * @ui_size: inode size used by UBIFS when writing to flash
> + * @parent_inum: inode number of the parent directory
>   * @flags: inode flags (@UBIFS_COMPR_FL, etc)
>   * @compr_type: default compression type used for this inode
>   * @last_page_read: page number of last page read (for bulk read)
> @@ -404,6 +405,7 @@ struct ubifs_inode {
>  	spinlock_t ui_lock;
>  	loff_t synced_i_size;
>  	loff_t ui_size;
> +	ino_t parent_inum;
>  	int flags;
>  	pgoff_t last_page_read;
>  	pgoff_t read_in_a_row;
> @@ -1012,6 +1014,7 @@ struct ubifs_debug_info;
>   * @space_fixup: flag indicating that free space in LEBs needs to be cleaned up
>   * @double_hash: flag indicating that we can do lookups by hash
>   * @encrypted: flag indicating that this file system contains encrypted files
> + * @parent_pointer: flag indicating that inodes have pointers to the parent dir
>   * @no_chk_data_crc: do not check CRCs when reading data nodes (except during
>   *                   recovery)
>   * @bulk_read: enable bulk-reads
> @@ -1255,6 +1258,7 @@ struct ubifs_info {
>  	unsigned int space_fixup:1;
>  	unsigned int double_hash:1;
>  	unsigned int encrypted:1;
> +	unsigned int parent_pointer:1;
>  	unsigned int no_chk_data_crc:1;
>  	unsigned int bulk_read:1;
>  	unsigned int default_compr:2;
> -- 
> 2.12.0
> 
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

-- 

Thanks,
Hyunchul

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