Message-ID: <87zk75paaj.fsf@devron.myhome.or.jp>
Date:	Thu, 12 Jul 2012 19:02:12 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	"Steven J. Magnani" <steve@...idescorp.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] fat (exportfs): move NFS support code

"Steven J. Magnani" <steve@...idescorp.com> writes:

> Move NFS-related code into its own C file.
> No functional changes.

Looks good.

Acked-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>

> Signed-off-by: Steven J. Magnani <steve@...idescorp.com>
> ---
> diff -uprN a/fs/fat/fat.h b/fs/fat/fat.h
> --- a/fs/fat/fat.h	2012-07-09 08:33:25.206615179 -0500
> +++ b/fs/fat/fat.h	2012-07-10 09:10:14.064615822 -0500
> @@ -341,6 +341,20 @@ extern int fat_fill_super(struct super_b
>  
>  extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
>  		            struct inode *i2);
> +static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
> +				    struct inode *inode)
> +{
> +	loff_t i_pos;
> +#if BITS_PER_LONG == 32
> +	spin_lock(&sbi->inode_hash_lock);
> +#endif
> +	i_pos = MSDOS_I(inode)->i_pos;
> +#if BITS_PER_LONG == 32
> +	spin_unlock(&sbi->inode_hash_lock);
> +#endif
> +	return i_pos;
> +}
> +
>  /* fat/misc.c */
>  extern __printf(3, 4) __cold
>  void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...);
> @@ -366,6 +380,14 @@ extern int fat_sync_bhs(struct buffer_he
>  int fat_cache_init(void);
>  void fat_cache_destroy(void);
>  
> +/* fat/nfs.c */
> +struct fid;
> +extern int fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp,
> +			 struct inode *parent);
> +extern struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
> +				       int fh_len, int fh_type);
> +extern struct dentry *fat_get_parent(struct dentry *child_dir);
> +
>  /* helper for printk */
>  typedef unsigned long long	llu;
>  
> diff -uprN a/fs/fat/inode.c b/fs/fat/inode.c
> --- a/fs/fat/inode.c	2012-07-09 08:33:25.249614939 -0500
> +++ b/fs/fat/inode.c	2012-07-10 09:09:58.654691584 -0500
> @@ -557,20 +557,6 @@ static int fat_statfs(struct dentry *den
>  	return 0;
>  }
>  
> -static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
> -				    struct inode *inode)
> -{
> -	loff_t i_pos;
> -#if BITS_PER_LONG == 32
> -	spin_lock(&sbi->inode_hash_lock);
> -#endif
> -	i_pos = MSDOS_I(inode)->i_pos;
> -#if BITS_PER_LONG == 32
> -	spin_unlock(&sbi->inode_hash_lock);
> -#endif
> -	return i_pos;
> -}
> -
>  static int __fat_write_inode(struct inode *inode, int wait)
>  {
>  	struct super_block *sb = inode->i_sb;
> @@ -663,122 +649,6 @@ static const struct super_operations fat
>  	.show_options	= fat_show_options,
>  };
>  
> -/*
> - * a FAT file handle with fhtype 3 is
> - *  0/  i_ino - for fast, reliable lookup if still in the cache
> - *  1/  i_generation - to see if i_ino is still valid
> - *          bit 0 == 0 iff directory
> - *  2/  i_pos(8-39) - if ino has changed, but still in cache
> - *  3/  i_pos(4-7)|i_logstart - to semi-verify inode found at i_pos
> - *  4/  i_pos(0-3)|parent->i_logstart - maybe used to hunt for the file on disc
> - *
> - * Hack for NFSv2: Maximum FAT entry number is 28bits and maximum
> - * i_pos is 40bits (blocknr(32) + dir offset(8)), so two 4bits
> - * of i_logstart is used to store the directory entry offset.
> - */
> -
> -static struct dentry *fat_fh_to_dentry(struct super_block *sb,
> -		struct fid *fid, int fh_len, int fh_type)
> -{
> -	struct inode *inode = NULL;
> -	u32 *fh = fid->raw;
> -
> -	if (fh_len < 5 || fh_type != 3)
> -		return NULL;
> -
> -	inode = ilookup(sb, fh[0]);
> -	if (!inode || inode->i_generation != fh[1]) {
> -		if (inode)
> -			iput(inode);
> -		inode = NULL;
> -	}
> -	if (!inode) {
> -		loff_t i_pos;
> -		int i_logstart = fh[3] & 0x0fffffff;
> -
> -		i_pos = (loff_t)fh[2] << 8;
> -		i_pos |= ((fh[3] >> 24) & 0xf0) | (fh[4] >> 28);
> -
> -		/* try 2 - see if i_pos is in F-d-c
> -		 * require i_logstart to be the same
> -		 * Will fail if you truncate and then re-write
> -		 */
> -
> -		inode = fat_iget(sb, i_pos);
> -		if (inode && MSDOS_I(inode)->i_logstart != i_logstart) {
> -			iput(inode);
> -			inode = NULL;
> -		}
> -	}
> -
> -	/*
> -	 * For now, do nothing if the inode is not found.
> -	 *
> -	 * What we could do is:
> -	 *
> -	 *	- follow the file starting at fh[4], and record the ".." entry,
> -	 *	  and the name of the fh[2] entry.
> -	 *	- then follow the ".." file finding the next step up.
> -	 *
> -	 * This way we build a path to the root of the tree. If this works, we
> -	 * lookup the path and so get this inode into the cache.  Finally try
> -	 * the fat_iget lookup again.  If that fails, then we are totally out
> -	 * of luck.  But all that is for another day
> -	 */
> -	return d_obtain_alias(inode);
> -}
> -
> -static int
> -fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp, struct inode *parent)
> -{
> -	int len = *lenp;
> -	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
> -	loff_t i_pos;
> -
> -	if (len < 5) {
> -		*lenp = 5;
> -		return 255; /* no room */
> -	}
> -
> -	i_pos = fat_i_pos_read(sbi, inode);
> -	*lenp = 5;
> -	fh[0] = inode->i_ino;
> -	fh[1] = inode->i_generation;
> -	fh[2] = i_pos >> 8;
> -	fh[3] = ((i_pos & 0xf0) << 24) | MSDOS_I(inode)->i_logstart;
> -	fh[4] = (i_pos & 0x0f) << 28;
> -	if (parent)
> -		fh[4] |= MSDOS_I(parent)->i_logstart;
> -	return 3;
> -}
> -
> -static struct dentry *fat_get_parent(struct dentry *child)
> -{
> -	struct super_block *sb = child->d_sb;
> -	struct buffer_head *bh;
> -	struct msdos_dir_entry *de;
> -	loff_t i_pos;
> -	struct dentry *parent;
> -	struct inode *inode;
> -	int err;
> -
> -	lock_super(sb);
> -
> -	err = fat_get_dotdot_entry(child->d_inode, &bh, &de, &i_pos);
> -	if (err) {
> -		parent = ERR_PTR(err);
> -		goto out;
> -	}
> -	inode = fat_build_inode(sb, de, i_pos);
> -	brelse(bh);
> -
> -	parent = d_obtain_alias(inode);
> -out:
> -	unlock_super(sb);
> -
> -	return parent;
> -}
> -
>  static const struct export_operations fat_export_ops = {
>  	.encode_fh	= fat_encode_fh,
>  	.fh_to_dentry	= fat_fh_to_dentry,
> diff -uprN a/fs/fat/Makefile b/fs/fat/Makefile
> --- a/fs/fat/Makefile	2012-07-09 08:33:25.240614990 -0500
> +++ b/fs/fat/Makefile	2012-07-09 08:33:25.370614268 -0500
> @@ -6,6 +6,6 @@ obj-$(CONFIG_FAT_FS) += fat.o
>  obj-$(CONFIG_VFAT_FS) += vfat.o
>  obj-$(CONFIG_MSDOS_FS) += msdos.o
>  
> -fat-y := cache.o dir.o fatent.o file.o inode.o misc.o
> +fat-y := cache.o dir.o fatent.o file.o inode.o misc.o nfs.o
>  vfat-y := namei_vfat.o
>  msdos-y := namei_msdos.o
> diff -uprN a/fs/fat/nfs.c b/fs/fat/nfs.c
> --- a/fs/fat/nfs.c	1969-12-31 18:00:00.000000000 -0600
> +++ b/fs/fat/nfs.c	2012-07-10 08:53:24.272703129 -0500
> @@ -0,0 +1,151 @@
> +/* fs/fat/nfs.c
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/exportfs.h>
> +#include "fat.h"
> +
> +/*
> + * a FAT file handle with fhtype 3 is
> + *  0/  i_ino - for fast, reliable lookup if still in the cache
> + *  1/  i_generation - to see if i_ino is still valid
> + *          bit 0 == 0 iff directory
> + *  2/  i_pos(8-39) - if ino has changed, but still in cache
> + *  3/  i_pos(4-7)|i_logstart - to semi-verify inode found at i_pos
> + *  4/  i_pos(0-3)|parent->i_logstart - maybe used to hunt for the file on disc
> + *
> + * Hack for NFSv2: Maximum FAT entry number is 28bits and maximum
> + * i_pos is 40bits (blocknr(32) + dir offset(8)), so two 4bits
> + * of i_logstart is used to store the directory entry offset.
> + */
> +
> +int
> +fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp, struct inode *parent)
> +{
> +	int len = *lenp;
> +	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
> +	loff_t i_pos;
> +
> +	if (len < 5) {
> +		*lenp = 5;
> +		return 255; /* no room */
> +	}
> +
> +	i_pos = fat_i_pos_read(sbi, inode);
> +	*lenp = 5;
> +	fh[0] = inode->i_ino;
> +	fh[1] = inode->i_generation;
> +	fh[2] = i_pos >> 8;
> +	fh[3] = ((i_pos & 0xf0) << 24) | MSDOS_I(inode)->i_logstart;
> +	fh[4] = (i_pos & 0x0f) << 28;
> +	if (parent)
> +		fh[4] |= MSDOS_I(parent)->i_logstart;
> +	return 3;
> +}
> +
> +static int fat_is_valid_fh(int fh_len, int fh_type)
> +{
> +	return ((fh_len >= 5) && (fh_type == 3));
> +}
> +
> +/**
> + * Map a NFS file handle to a corresponding dentry.
> + * The dentry may or may not be connected to the filesystem root.
> + */
> +struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
> +				int fh_len, int fh_type)
> +{
> +	struct inode *inode = NULL;
> +	u32 *fh = fid->raw;
> +	loff_t i_pos;
> +	unsigned long i_ino;
> +	__u32 i_generation;
> +	int i_logstart;
> +
> +	if (!fat_is_valid_fh(fh_len, fh_type))
> +		return NULL;
> +
> +	i_ino = fh[0];
> +	i_generation = fh[1];
> +	i_logstart = fh[3] & 0x0fffffff;
> +
> +	/* Try i_ino lookup first - fastest and most reliable */
> +	inode = ilookup(sb, i_ino);
> +	if (inode && (inode->i_generation != i_generation)) {
> +		iput(inode);
> +		inode = NULL;
> +	}
> +	if (!inode) {
> +		i_pos = (loff_t)fh[2] << 8;
> +		i_pos |= ((fh[3] >> 24) & 0xf0) | (fh[4] >> 28);
> +
> +		/* try 2 - see if i_pos is in F-d-c
> +		 * require i_logstart to be the same
> +		 * Will fail if you truncate and then re-write
> +		 */
> +
> +		inode = fat_iget(sb, i_pos);
> +		if (inode && MSDOS_I(inode)->i_logstart != i_logstart) {
> +			iput(inode);
> +			inode = NULL;
> +		}
> +	}
> +
> +	/*
> +	 * For now, do nothing if the inode is not found.
> +	 *
> +	 * What we could do is:
> +	 *
> +	 *	- follow the file starting at fh[4], and record the ".." entry,
> +	 *	  and the name of the fh[2] entry.
> +	 *	- then follow the ".." file finding the next step up.
> +	 *
> +	 * This way we build a path to the root of the tree. If this works, we
> +	 * lookup the path and so get this inode into the cache.  Finally try
> +	 * the fat_iget lookup again.  If that fails, then we are totally out
> +	 * of luck.  But all that is for another day
> +	 */
> +	return d_obtain_alias(inode);
> +}
> +
> +/*
> + * Find the parent for a directory that is not currently connected to
> + * the filesystem root.
> + *
> + * On entry, the caller holds child_dir->d_inode->i_mutex.
> + */
> +struct dentry *fat_get_parent(struct dentry *child_dir)
> +{
> +	struct super_block *sb = child_dir->d_sb;
> +	struct buffer_head *bh = NULL;
> +	struct msdos_dir_entry *de;
> +	loff_t i_pos;
> +	struct dentry *parent;
> +	struct inode *inode;
> +	int err;
> +
> +	lock_super(sb);
> +
> +	err = fat_get_dotdot_entry(child_dir->d_inode, &bh, &de, &i_pos);
> +	if (err) {
> +		parent = ERR_PTR(err);
> +		goto out;
> +	}
> +	inode = fat_build_inode(sb, de, i_pos);
> +
> +	parent = d_obtain_alias(inode);
> +out:
> +	brelse(bh);
> +	unlock_super(sb);
> +
> +	return parent;
> +}
>

-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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