linux-kernel - Re: [PATCH] knfsd: add nfs-export support to ramfs

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Message-ID: <CAGsJ_4wOdLhR3gSE8Fpy5D7Tic1DDQw=AwOkXEz0MgrjxKNG2g@mail.gmail.com>
Date:   Sun, 21 Jul 2019 03:25:18 +1200
From:   Barry Song <21cnbao@...il.com>
To:     Haodong Wong <haydenw.kernel@...il.com>
Cc:     haodwang@...co.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] knfsd: add nfs-export support to ramfs

the subject is unsuitable? i mean the prefix should be fs/ramfs rather
than knfsd?

2019-05-22 3:25 GMT+12:00, Haodong Wong <haydenw.kernel@...il.com>:
> Refer to tmpfs, use inode number and generation number
> to construct the filehandle for nfs-export

would you like to describe what is happening without this patch?

BTW, i guess you can keep Andrew Morton in the loop to review the
patch when you resend it.

>
> Signed-off-by: Haodong Wong <haydenw.kernel@...il.com>
> ---
>  fs/ramfs/inode.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
>
> diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
> index 11201b2d06b9..418b2551f6fd 100644
> --- a/fs/ramfs/inode.c
> +++ b/fs/ramfs/inode.c
> @@ -36,6 +36,7 @@
>  #include <linux/magic.h>
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
> +#include <linux/exportfs.h>
>  #include "internal.h"
>
>  struct ramfs_mount_opts {
> @@ -66,6 +67,7 @@ struct inode *ramfs_get_inode(struct super_block *sb,
>  	if (inode) {
>  		inode->i_ino = get_next_ino();
>  		inode_init_owner(inode, dir, mode);
> +		inode->i_generation = get_seconds();
>  		inode->i_mapping->a_ops = &ramfs_aops;
>  		mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
>  		mapping_set_unevictable(inode->i_mapping);
> @@ -217,6 +219,75 @@ static int ramfs_parse_options(char *data, struct
> ramfs_mount_opts *opts)
>  	return 0;
>  }
>
> +static struct dentry *ramfs_get_parent(struct dentry *child)
> +{
> +	return ERR_PTR(-ESTALE);
> +}
> +
> +static int ramfs_match(struct inode *ino, void *vfh)
> +{
> +	__u32 *fh = vfh;
> +	__u64 inum = fh[2];
> +
> +	inum = (inum << 32) | fh[1];
> +	return ino->i_ino == inum && fh[0] == ino->i_generation;
> +}
> +
> +static struct dentry *ramfs_fh_to_dentry(struct super_block *sb,
> +			   struct fid *fid, int fh_len, int fh_type)
> +
> +{
> +	struct inode *inode;
> +	struct dentry *dentry = NULL;
> +	u64 inum;
> +
> +	if (fh_len < 3)
> +		return NULL;
> +
> +	inum = fid->raw[2];
> +	inum = (inum << 32) | fid->raw[1];
> +	inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
> +				ramfs_match, fid->raw);
> +
> +	if (inode) {
> +		dentry = d_find_alias(inode);
> +		iput(inode);
> +	}
> +
> +	return dentry;
> +}
> +
> +static int ramfs_encode_fh(struct inode *inode, __u32 *fh, int *len,
> +			   struct inode *parent)
> +{
> +	if (*len < 3) {
> +		*len = 3;
> +		return FILEID_INVALID;
> +	}
> +
> +	if (inode_unhashed(inode)) {
> +		static DEFINE_SPINLOCK(lock);
> +
> +		spin_lock(&lock);
> +		if (inode_unhashed(inode))
> +			__insert_inode_hash(inode,
> +				inode->i_ino + inode->i_generation);
> +		spin_unlock(&lock);
> +	}
> +	fh[0] = inode->i_generation;
> +	fh[1] = inode->i_ino;
> +	fh[2] = ((__u64)inode->i_ino) >> 32;
> +
> +	*len = 3;
> +	return 1;
> +}
> +
> +static const struct export_operations ramfs_export_ops = {
> +	.get_parent     = ramfs_get_parent,
> +	.encode_fh      = ramfs_encode_fh,
> +	.fh_to_dentry   = ramfs_fh_to_dentry,
> +};
> +
>  int ramfs_fill_super(struct super_block *sb, void *data, int silent)
>  {
>  	struct ramfs_fs_info *fsi;
> @@ -238,6 +309,7 @@ int ramfs_fill_super(struct super_block *sb, void *data,
> int silent)
>  	sb->s_magic		= RAMFS_MAGIC;
>  	sb->s_op		= &ramfs_ops;
>  	sb->s_time_gran		= 1;
> +	sb->s_export_op         = &ramfs_export_ops;
>
>  	inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
>  	sb->s_root = d_make_root(inode);
> --
> 2.17.1
>
>

-barry