Re: [PATCH -V11 1/9] exportfs: Return the minimum required handlesize

[J. Bruce Fields]

On Thu, May 20, 2010 at 01:05:30PM +0530, Aneesh Kumar K.V wrote:
> The exportfs encode handle function should return the minimum required
> handle size. This helps user to find out the handle size by passing 0
> handle size in the first step and then redoing to the call again with
> the returned handle size value.

The encode_fh() interface is a little confusing.  (Not your fault,
really, mainly it's the return value (and the special use of 255) that I
always find odd.)

But maybe it would help to have a little more documention in the
export_encode_fh() kerneldoc comment and/or in
Documentation/filesystems/nfs/Exporting?

--b.

> 
> Acked-by: Serge Hallyn <serue@xxxxxxxxxx>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
>  fs/btrfs/export.c             |    8 ++++++--
>  fs/exportfs/expfs.c           |    9 +++++++--
>  fs/fat/inode.c                |    4 +++-
>  fs/fuse/inode.c               |    4 +++-
>  fs/gfs2/export.c              |    8 ++++++--
>  fs/isofs/export.c             |    8 ++++++--
>  fs/ocfs2/export.c             |    8 +++++++-
>  fs/reiserfs/inode.c           |    7 ++++++-
>  fs/udf/namei.c                |    7 ++++++-
>  fs/xfs/linux-2.6/xfs_export.c |    4 +++-
>  mm/shmem.c                    |    4 +++-
>  11 files changed, 56 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
> index 951ef09..5f8ee5a 100644
> --- a/fs/btrfs/export.c
> +++ b/fs/btrfs/export.c
> @@ -21,9 +21,13 @@ static int btrfs_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
>  	int len = *max_len;
>  	int type;
>  
> -	if ((len < BTRFS_FID_SIZE_NON_CONNECTABLE) ||
> -	    (connectable && len < BTRFS_FID_SIZE_CONNECTABLE))
> +	if (connectable && (len < BTRFS_FID_SIZE_CONNECTABLE)) {
> +		*max_len = BTRFS_FID_SIZE_CONNECTABLE;
>  		return 255;
> +	} else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
> +		*max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;
> +		return 255;
> +	}
>  
>  	len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
>  	type = FILEID_BTRFS_WITHOUT_PARENT;
> diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> index e9e1759..cfee0f0 100644
> --- a/fs/exportfs/expfs.c
> +++ b/fs/exportfs/expfs.c
> @@ -319,9 +319,14 @@ static int export_encode_fh(struct dentry *dentry, struct fid *fid,
>  	struct inode * inode = dentry->d_inode;
>  	int len = *max_len;
>  	int type = FILEID_INO32_GEN;
> -	
> -	if (len < 2 || (connectable && len < 4))
> +
> +	if (connectable && (len < 4)) {
> +		*max_len = 4;
> +		return 255;
> +	} else if (len < 2) {
> +		*max_len = 2;
>  		return 255;
> +	}
>  
>  	len = 2;
>  	fid->i32.ino = inode->i_ino;
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index 0ce143b..6f83bc7 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -738,8 +738,10 @@ fat_encode_fh(struct dentry *de, __u32 *fh, int *lenp, int connectable)
>  	struct inode *inode =  de->d_inode;
>  	u32 ipos_h, ipos_m, ipos_l;
>  
> -	if (len < 5)
> +	if (len < 5) {
> +		*lenp = 5;
>  		return 255; /* no room */
> +	}
>  
>  	ipos_h = MSDOS_I(inode)->i_pos >> 8;
>  	ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index ec14d19..beaea69 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -638,8 +638,10 @@ static int fuse_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
>  	u64 nodeid;
>  	u32 generation;
>  
> -	if (*max_len < len)
> +	if (*max_len < len) {
> +		*max_len = len;
>  		return  255;
> +	}
>  
>  	nodeid = get_fuse_inode(inode)->nodeid;
>  	generation = inode->i_generation;
> diff --git a/fs/gfs2/export.c b/fs/gfs2/export.c
> index c22c211..d022236 100644
> --- a/fs/gfs2/export.c
> +++ b/fs/gfs2/export.c
> @@ -36,9 +36,13 @@ static int gfs2_encode_fh(struct dentry *dentry, __u32 *p, int *len,
>  	struct super_block *sb = inode->i_sb;
>  	struct gfs2_inode *ip = GFS2_I(inode);
>  
> -	if (*len < GFS2_SMALL_FH_SIZE ||
> -	    (connectable && *len < GFS2_LARGE_FH_SIZE))
> +	if (connectable && (*len < GFS2_LARGE_FH_SIZE)) {
> +		*len = GFS2_LARGE_FH_SIZE;
>  		return 255;
> +	} else if (*len < GFS2_SMALL_FH_SIZE) {
> +		*len = GFS2_SMALL_FH_SIZE;
> +		return 255;
> +	}
>  
>  	fh[0] = cpu_to_be32(ip->i_no_formal_ino >> 32);
>  	fh[1] = cpu_to_be32(ip->i_no_formal_ino & 0xFFFFFFFF);
> diff --git a/fs/isofs/export.c b/fs/isofs/export.c
> index ed752cb..dd4687f 100644
> --- a/fs/isofs/export.c
> +++ b/fs/isofs/export.c
> @@ -124,9 +124,13 @@ isofs_export_encode_fh(struct dentry *dentry,
>  	 * offset of the inode and the upper 16 bits of fh32[1] to
>  	 * hold the offset of the parent.
>  	 */
> -
> -	if (len < 3 || (connectable && len < 5))
> +	if (connectable && (len < 5)) {
> +		*max_len = 5;
> +		return 255;
> +	} else if (len < 3) {
> +		*max_len = 3;
>  		return 255;
> +	}
>  
>  	len = 3;
>  	fh32[0] = ei->i_iget5_block;
> diff --git a/fs/ocfs2/export.c b/fs/ocfs2/export.c
> index 19ad145..250a347 100644
> --- a/fs/ocfs2/export.c
> +++ b/fs/ocfs2/export.c
> @@ -201,8 +201,14 @@ static int ocfs2_encode_fh(struct dentry *dentry, u32 *fh_in, int *max_len,
>  		   dentry->d_name.len, dentry->d_name.name,
>  		   fh, len, connectable);
>  
> -	if (len < 3 || (connectable && len < 6)) {
> +	if (connectable && (len < 6)) {
>  		mlog(ML_ERROR, "fh buffer is too small for encoding\n");
> +		*max_len = 6;
> +		type = 255;
> +		goto bail;
> +	} else if (len < 3) {
> +		mlog(ML_ERROR, "fh buffer is too small for encoding\n");
> +		*max_len = 3;
>  		type = 255;
>  		goto bail;
>  	}
> diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
> index dc2c65e..5fff1e2 100644
> --- a/fs/reiserfs/inode.c
> +++ b/fs/reiserfs/inode.c
> @@ -1588,8 +1588,13 @@ int reiserfs_encode_fh(struct dentry *dentry, __u32 * data, int *lenp,
>  	struct inode *inode = dentry->d_inode;
>  	int maxlen = *lenp;
>  
> -	if (maxlen < 3)
> +	if (need_parent && (maxlen < 5)) {
> +		*lenp = 5;
>  		return 255;
> +	} else if (maxlen < 3) {
> +		*lenp = 3;
> +		return 255;
> +	}
>  
>  	data[0] = inode->i_ino;
>  	data[1] = le32_to_cpu(INODE_PKEY(inode)->k_dir_id);
> diff --git a/fs/udf/namei.c b/fs/udf/namei.c
> index 7581602..37ce713 100644
> --- a/fs/udf/namei.c
> +++ b/fs/udf/namei.c
> @@ -1360,8 +1360,13 @@ static int udf_encode_fh(struct dentry *de, __u32 *fh, int *lenp,
>  	struct fid *fid = (struct fid *)fh;
>  	int type = FILEID_UDF_WITHOUT_PARENT;
>  
> -	if (len < 3 || (connectable && len < 5))
> +	if (connectable && (len < 5)) {
> +		*lenp = 5;
> +		return 255;
> +	} else if (len < 3) {
> +		*lenp = 3;
>  		return 255;
> +	}
>  
>  	*lenp = 3;
>  	fid->udf.block = location.logicalBlockNum;
> diff --git a/fs/xfs/linux-2.6/xfs_export.c b/fs/xfs/linux-2.6/xfs_export.c
> index 846b75a..82c0553 100644
> --- a/fs/xfs/linux-2.6/xfs_export.c
> +++ b/fs/xfs/linux-2.6/xfs_export.c
> @@ -81,8 +81,10 @@ xfs_fs_encode_fh(
>  	 * seven combinations work.  The real answer is "don't use v2".
>  	 */
>  	len = xfs_fileid_length(fileid_type);
> -	if (*max_len < len)
> +	if (*max_len < len) {
> +		*max_len = len
>  		return 255;
> +	}
>  	*max_len = len;
>  
>  	switch (fileid_type) {
> diff --git a/mm/shmem.c b/mm/shmem.c
> index eef4ebe..bbeda1c 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2125,8 +2125,10 @@ static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
>  {
>  	struct inode *inode = dentry->d_inode;
>  
> -	if (*len < 3)
> +	if (*len < 3) {
> +		*len = 3;
>  		return 255;
> +	}
>  
>  	if (hlist_unhashed(&inode->i_hash)) {
>  		/* Unfortunately insert_inode_hash is not idempotent,
> -- 
> 1.7.1.78.g212f0
> 
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