Re: [PATCH 3/9] xfs: cull unnecessary icdinode fields

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On Mon, Feb 08, 2016 at 03:24:15PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> Now that the struct xfs_icdinode is not directly related to the
> on-disk format, we can cull things in it we really don't need to
> store:
> 
> 	- magic number never changes
> 	- padding is not necessary
> 	- next_unlinked is never used
> 	- inode number is redundant
> 	- uuid is redundant
> 	- lsn is accessed directly from dinode
> 	- inode CRC is only accessed directly from dinode
> 
> Hence we can remove these from the struct xfs_icdinode and redirect
> the code that uses them to the xfs_dinode appripriately.  This
> reduces the size of the struct icdinode from 152 bytes to 88 bytes,
> and removes a fair chunk of unnecessary code, too.
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

>  fs/xfs/libxfs/xfs_inode_buf.c | 39 +++++++++++++--------------------------
>  fs/xfs/libxfs/xfs_inode_buf.h | 25 ++++++-------------------
>  fs/xfs/xfs_inode.c            | 19 +------------------
>  fs/xfs/xfs_inode_item.c       | 19 +++++++++++--------
>  4 files changed, 31 insertions(+), 71 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> index 26e3c46..17ff4e8 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> @@ -202,7 +202,6 @@ xfs_inode_from_disk(
>  	struct xfs_icdinode	*to = &ip->i_d;
>  	struct inode		*inode = VFS_I(ip);
>  
> -	to->di_magic = be16_to_cpu(from->di_magic);
>  	to->di_mode = be16_to_cpu(from->di_mode);
>  	to->di_version = from ->di_version;
>  	to->di_format = from->di_format;
> @@ -212,7 +211,6 @@ xfs_inode_from_disk(
>  	to->di_nlink = be32_to_cpu(from->di_nlink);
>  	to->di_projid_lo = be16_to_cpu(from->di_projid_lo);
>  	to->di_projid_hi = be16_to_cpu(from->di_projid_hi);
> -	memcpy(to->di_pad, from->di_pad, sizeof(to->di_pad));
>  	to->di_flushiter = be16_to_cpu(from->di_flushiter);
>  
>  	/*
> @@ -245,24 +243,22 @@ xfs_inode_from_disk(
>  		to->di_crtime.t_sec = be32_to_cpu(from->di_crtime.t_sec);
>  		to->di_crtime.t_nsec = be32_to_cpu(from->di_crtime.t_nsec);
>  		to->di_flags2 = be64_to_cpu(from->di_flags2);
> -		to->di_ino = be64_to_cpu(from->di_ino);
> -		to->di_lsn = be64_to_cpu(from->di_lsn);
> -		memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
> -		uuid_copy(&to->di_uuid, &from->di_uuid);
>  	}
>  }
>  
>  void
>  xfs_inode_to_disk(
>  	struct xfs_inode	*ip,
> -	struct xfs_dinode	*to)
> +	struct xfs_dinode	*to,
> +	xfs_lsn_t		lsn)
>  {
>  	struct xfs_icdinode	*from = &ip->i_d;
>  	struct inode		*inode = VFS_I(ip);
>  
> -	to->di_magic = cpu_to_be16(from->di_magic);
> +	to->di_magic = cpu_to_be16(XFS_DINODE_MAGIC);
> +
>  	to->di_mode = cpu_to_be16(from->di_mode);
> -	to->di_version = from ->di_version;
> +	to->di_version = from->di_version;
>  	to->di_format = from->di_format;
>  	to->di_onlink = cpu_to_be16(from->di_onlink);
>  	to->di_uid = cpu_to_be32(from->di_uid);
> @@ -270,8 +266,8 @@ xfs_inode_to_disk(
>  	to->di_nlink = cpu_to_be32(from->di_nlink);
>  	to->di_projid_lo = cpu_to_be16(from->di_projid_lo);
>  	to->di_projid_hi = cpu_to_be16(from->di_projid_hi);
> -	memcpy(to->di_pad, from->di_pad, sizeof(to->di_pad));
>  
> +	memset(to->di_pad, 0, sizeof(to->di_pad));
>  	to->di_atime.t_sec = cpu_to_be32(inode->i_atime.tv_sec);
>  	to->di_atime.t_nsec = cpu_to_be32(inode->i_atime.tv_nsec);
>  	to->di_mtime.t_sec = cpu_to_be32(inode->i_mtime.tv_sec);
> @@ -296,10 +292,11 @@ xfs_inode_to_disk(
>  		to->di_crtime.t_sec = cpu_to_be32(from->di_crtime.t_sec);
>  		to->di_crtime.t_nsec = cpu_to_be32(from->di_crtime.t_nsec);
>  		to->di_flags2 = cpu_to_be64(from->di_flags2);
> -		to->di_ino = cpu_to_be64(from->di_ino);
> -		to->di_lsn = cpu_to_be64(from->di_lsn);
> -		memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
> -		uuid_copy(&to->di_uuid, &from->di_uuid);
> +
> +		to->di_ino = cpu_to_be64(ip->i_ino);
> +		to->di_lsn = cpu_to_be64(lsn);
> +		memset(to->di_pad2, 0, sizeof(to->di_pad2));
> +		uuid_copy(&to->di_uuid, &ip->i_mount->m_sb.sb_meta_uuid);
>  		to->di_flushiter = 0;
>  	} else {
>  		to->di_flushiter = cpu_to_be16(from->di_flushiter);
> @@ -434,13 +431,10 @@ xfs_iread(
>  	    !(mp->m_flags & XFS_MOUNT_IKEEP)) {
>  		/* initialise the on-disk inode core */
>  		memset(&ip->i_d, 0, sizeof(ip->i_d));
> -		ip->i_d.di_magic = XFS_DINODE_MAGIC;
>  		ip->i_d.di_gen = prandom_u32();
> -		if (xfs_sb_version_hascrc(&mp->m_sb)) {
> +		if (xfs_sb_version_hascrc(&mp->m_sb))
>  			ip->i_d.di_version = 3;
> -			ip->i_d.di_ino = ip->i_ino;
> -			uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid);
> -		} else
> +		else
>  			ip->i_d.di_version = 2;
>  		return 0;
>  	}
> @@ -484,16 +478,10 @@ xfs_iread(
>  		 * Partial initialisation of the in-core inode. Just the bits
>  		 * that xfs_ialloc won't overwrite or relies on being correct.
>  		 */
> -		ip->i_d.di_magic = be16_to_cpu(dip->di_magic);
>  		ip->i_d.di_version = dip->di_version;
>  		ip->i_d.di_gen = be32_to_cpu(dip->di_gen);
>  		ip->i_d.di_flushiter = be16_to_cpu(dip->di_flushiter);
>  
> -		if (dip->di_version == 3) {
> -			ip->i_d.di_ino = be64_to_cpu(dip->di_ino);
> -			uuid_copy(&ip->i_d.di_uuid, &dip->di_uuid);
> -		}
> -
>  		/*
>  		 * Make sure to pull in the mode here as well in
>  		 * case the inode is released without being used.
> @@ -514,7 +502,6 @@ xfs_iread(
>  	 */
>  	if (ip->i_d.di_version == 1) {
>  		ip->i_d.di_version = 2;
> -		memset(&(ip->i_d.di_pad[0]), 0, sizeof(ip->i_d.di_pad));
>  		ip->i_d.di_nlink = ip->i_d.di_onlink;
>  		ip->i_d.di_onlink = 0;
>  		xfs_set_projid(ip, 0);
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.h b/fs/xfs/libxfs/xfs_inode_buf.h
> index adcc9bf..7b8b1b9 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.h
> +++ b/fs/xfs/libxfs/xfs_inode_buf.h
> @@ -22,24 +22,22 @@ struct xfs_inode;
>  struct xfs_dinode;
>  
>  /*
> - * In memory representation of the XFS inode. This is held in the in-core
> - * struct xfs_inode to represent the on disk values, but no longer needs to be
> - * identical to the on-disk structure as it is always translated to on-disk
> + * In memory representation of the XFS inode. This is held in the in-core struct
> + * xfs_inode and represents the current on disk values but the structure is not
> + * in on-disk format.  That is, this structure is always translated to on-disk
>   * format specific structures at the appropriate time.
>   */
>  struct xfs_icdinode {
> -	__uint16_t	di_magic;	/* inode magic # = XFS_DINODE_MAGIC */
>  	__uint16_t	di_mode;	/* mode and type of file */
>  	__int8_t	di_version;	/* inode version */
>  	__int8_t	di_format;	/* format of di_c data */
>  	__uint16_t	di_onlink;	/* old number of links to file */
> +	__uint16_t	di_flushiter;	/* incremented on flush */
>  	__uint32_t	di_uid;		/* owner's user id */
>  	__uint32_t	di_gid;		/* owner's group id */
>  	__uint32_t	di_nlink;	/* number of links to file */
>  	__uint16_t	di_projid_lo;	/* lower part of owner's project id */
>  	__uint16_t	di_projid_hi;	/* higher part of owner's project id */
> -	__uint8_t	di_pad[6];	/* unused, zeroed space */
> -	__uint16_t	di_flushiter;	/* incremented on flush */
>  	xfs_fsize_t	di_size;	/* number of bytes in file */
>  	xfs_rfsblock_t	di_nblocks;	/* # of direct & btree blocks used */
>  	xfs_extlen_t	di_extsize;	/* basic/minimum extent size for file */
> @@ -52,22 +50,10 @@ struct xfs_icdinode {
>  	__uint16_t	di_flags;	/* random flags, XFS_DIFLAG_... */
>  	__uint32_t	di_gen;		/* generation number */
>  
> -	/* di_next_unlinked is the only non-core field in the old dinode */
> -	xfs_agino_t	di_next_unlinked;/* agi unlinked list ptr */
> -
> -	/* start of the extended dinode, writable fields */
> -	__uint32_t	di_crc;		/* CRC of the inode */
>  	__uint64_t	di_changecount;	/* number of attribute changes */
> -	xfs_lsn_t	di_lsn;		/* flush sequence */
>  	__uint64_t	di_flags2;	/* more random flags */
> -	__uint8_t	di_pad2[16];	/* more padding for future expansion */
>  
> -	/* fields only written to during inode creation */
>  	xfs_ictimestamp_t di_crtime;	/* time created */
> -	xfs_ino_t	di_ino;		/* inode number */
> -	uuid_t		di_uuid;	/* UUID of the filesystem */
> -
> -	/* structure must be padded to 64 bit alignment */
>  };
>  
>  /*
> @@ -86,7 +72,8 @@ int	xfs_imap_to_bp(struct xfs_mount *, struct xfs_trans *,
>  int	xfs_iread(struct xfs_mount *, struct xfs_trans *,
>  		  struct xfs_inode *, uint);
>  void	xfs_dinode_calc_crc(struct xfs_mount *, struct xfs_dinode *);
> -void	xfs_inode_to_disk(struct xfs_inode *ip, struct xfs_dinode *to);
> +void	xfs_inode_to_disk(struct xfs_inode *ip, struct xfs_dinode *to,
> +			  xfs_lsn_t lsn);
>  void	xfs_inode_from_disk(struct xfs_inode *ip, struct xfs_dinode *from);
>  void	xfs_log_dinode_to_disk(struct xfs_log_dinode *from,
>  			       struct xfs_dinode *to);
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 9ad9e35..45acdee 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -809,7 +809,6 @@ xfs_ialloc(
>  	ip->i_d.di_uid = xfs_kuid_to_uid(current_fsuid());
>  	ip->i_d.di_gid = xfs_kgid_to_gid(current_fsgid());
>  	xfs_set_projid(ip, prid);
> -	memset(&(ip->i_d.di_pad[0]), 0, sizeof(ip->i_d.di_pad));
>  
>  	if (pip && XFS_INHERIT_GID(pip)) {
>  		ip->i_d.di_gid = pip->i_d.di_gid;
> @@ -847,13 +846,8 @@ xfs_ialloc(
>  	ip->i_d.di_flags = 0;
>  
>  	if (ip->i_d.di_version == 3) {
> -		ASSERT(ip->i_d.di_ino == ino);
> -		ASSERT(uuid_equal(&ip->i_d.di_uuid, &mp->m_sb.sb_meta_uuid));
> -		ip->i_d.di_crc = 0;
>  		ip->i_d.di_changecount = 1;
> -		ip->i_d.di_lsn = 0;
>  		ip->i_d.di_flags2 = 0;
> -		memset(&(ip->i_d.di_pad2[0]), 0, sizeof(ip->i_d.di_pad2));
>  		ip->i_d.di_crtime.t_sec = (__int32_t)tv.tv_sec;
>  		ip->i_d.di_crtime.t_nsec = (__int32_t)tv.tv_nsec;
>  	}
> @@ -3464,13 +3458,6 @@ xfs_iflush_int(
>  			__func__, ip->i_ino, be16_to_cpu(dip->di_magic), dip);
>  		goto corrupt_out;
>  	}
> -	if (XFS_TEST_ERROR(ip->i_d.di_magic != XFS_DINODE_MAGIC,
> -				mp, XFS_ERRTAG_IFLUSH_2, XFS_RANDOM_IFLUSH_2)) {
> -		xfs_alert_tag(mp, XFS_PTAG_IFLUSH,
> -			"%s: Bad inode %Lu, ptr 0x%p, magic number 0x%x",
> -			__func__, ip->i_ino, ip, ip->i_d.di_magic);
> -		goto corrupt_out;
> -	}
>  	if (S_ISREG(ip->i_d.di_mode)) {
>  		if (XFS_TEST_ERROR(
>  		    (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS) &&
> @@ -3529,7 +3516,7 @@ xfs_iflush_int(
>  	 * copy out the core of the inode, because if the inode is dirty at all
>  	 * the core must be.
>  	 */
> -	xfs_inode_to_disk(ip, dip);
> +	xfs_inode_to_disk(ip, dip, iip->ili_item.li_lsn);
>  
>  	/* Wrap, we never let the log put out DI_MAX_FLUSH */
>  	if (ip->i_d.di_flushiter == DI_MAX_FLUSH)
> @@ -3581,10 +3568,6 @@ xfs_iflush_int(
>  	 */
>  	xfs_buf_attach_iodone(bp, xfs_iflush_done, &iip->ili_item);
>  
> -	/* update the lsn in the on disk inode if required */
> -	if (ip->i_d.di_version == 3)
> -		dip->di_lsn = cpu_to_be64(iip->ili_item.li_lsn);
> -
>  	/* generate the checksum. */
>  	xfs_dinode_calc_crc(mp, dip);
>  
> diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
> index 9dcbf58..588d1b4 100644
> --- a/fs/xfs/xfs_inode_item.c
> +++ b/fs/xfs/xfs_inode_item.c
> @@ -325,12 +325,14 @@ xfs_inode_item_format_attr_fork(
>  static void
>  xfs_inode_to_log_dinode(
>  	struct xfs_inode	*ip,
> -	struct xfs_log_dinode	*to)
> +	struct xfs_log_dinode	*to,
> +	xfs_lsn_t		lsn)
>  {
>  	struct xfs_icdinode	*from = &ip->i_d;
>  	struct inode		*inode = VFS_I(ip);
>  
> -	to->di_magic = from->di_magic;
> +	to->di_magic = XFS_DINODE_MAGIC;
> +
>  	to->di_mode = from->di_mode;
>  	to->di_version = from->di_version;
>  	to->di_format = from->di_format;
> @@ -340,8 +342,8 @@ xfs_inode_to_log_dinode(
>  	to->di_nlink = from->di_nlink;
>  	to->di_projid_lo = from->di_projid_lo;
>  	to->di_projid_hi = from->di_projid_hi;
> -	memcpy(to->di_pad, from->di_pad, sizeof(to->di_pad));
>  
> +	memset(to->di_pad, 0, sizeof(to->di_pad));
>  	to->di_atime.t_sec = inode->i_atime.tv_sec;
>  	to->di_atime.t_nsec = inode->i_atime.tv_nsec;
>  	to->di_mtime.t_sec = inode->i_mtime.tv_sec;
> @@ -366,10 +368,11 @@ xfs_inode_to_log_dinode(
>  		to->di_crtime.t_sec = from->di_crtime.t_sec;
>  		to->di_crtime.t_nsec = from->di_crtime.t_nsec;
>  		to->di_flags2 = from->di_flags2;
> -		to->di_ino = from->di_ino;
> -		to->di_lsn = from->di_lsn;
> -		memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
> -		uuid_copy(&to->di_uuid, &from->di_uuid);
> +
> +		to->di_ino = ip->i_ino;
> +		to->di_lsn = lsn;
> +		memset(to->di_pad2, 0, sizeof(to->di_pad2));
> +		uuid_copy(&to->di_uuid, &ip->i_mount->m_sb.sb_meta_uuid);
>  		to->di_flushiter = 0;
>  	} else {
>  		to->di_flushiter = from->di_flushiter;
> @@ -390,7 +393,7 @@ xfs_inode_item_format_core(
>  	struct xfs_log_dinode	*dic;
>  
>  	dic = xlog_prepare_iovec(lv, vecp, XLOG_REG_TYPE_ICORE);
> -	xfs_inode_to_log_dinode(ip, dic);
> +	xfs_inode_to_log_dinode(ip, dic, ip->i_itemp->ili_item.li_lsn);
>  	xlog_finish_iovec(lv, *vecp, xfs_log_dinode_size(ip->i_d.di_version));
>  }
>  
> -- 
> 2.5.0
> 
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