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/* 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"
struct fat_fid {
u32 i_gen;
u32 i_pos_low;
u16 i_pos_hi;
u16 parent_i_pos_hi;
u32 parent_i_pos_low;
u32 parent_i_gen;
};
#define FAT_FID_SIZE_WITHOUT_PARENT 3
#define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32))
/**
* Look up a directory inode given its starting cluster.
*/
static struct inode *fat_dget(struct super_block *sb, int i_logstart)
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
struct hlist_head *head;
struct msdos_inode_info *i;
struct inode *inode = NULL;
head = sbi->dir_hashtable + fat_dir_hash(i_logstart);
spin_lock(&sbi->dir_hash_lock);
hlist_for_each_entry(i, head, i_dir_hash) {
BUG_ON(i->vfs_inode.i_sb != sb);
if (i->i_logstart != i_logstart)
continue;
inode = igrab(&i->vfs_inode);
if (inode)
break;
}
spin_unlock(&sbi->dir_hash_lock);
return inode;
}
static struct inode *__fat_nfs_get_inode(struct super_block *sb,
u64 ino, u32 generation, loff_t i_pos)
{
struct inode *inode;
if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
return NULL;
inode = ilookup(sb, ino);
if (inode && generation && (inode->i_generation != generation)) {
iput(inode);
inode = NULL;
}
return inode;
}
static struct inode *fat_nfs_get_inode(struct super_block *sb,
u64 ino, u32 generation)
{
return __fat_nfs_get_inode(sb, ino, generation, 0);
}
static int
fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp,
struct inode *parent)
{
int len = *lenp;
struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
struct fat_fid *fid = (struct fat_fid *) fh;
loff_t i_pos;
int type = FILEID_FAT_WITHOUT_PARENT;
if (parent) {
if (len < FAT_FID_SIZE_WITH_PARENT) {
*lenp = FAT_FID_SIZE_WITH_PARENT;
return FILEID_INVALID;
}
} else {
if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
return FILEID_INVALID;
}
}
i_pos = fat_i_pos_read(sbi, inode);
*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
fid->i_gen = inode->i_generation;
fid->i_pos_low = i_pos & 0xFFFFFFFF;
fid->i_pos_hi = (i_pos >> 32) & 0xFFFF;
if (parent) {
i_pos = fat_i_pos_read(sbi, parent);
fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF;
fid->parent_i_pos_low = i_pos & 0xFFFFFFFF;
fid->parent_i_gen = parent->i_generation;
type = FILEID_FAT_WITH_PARENT;
*lenp = FAT_FID_SIZE_WITH_PARENT;
}
return type;
}
/**
* Map a NFS file handle to a corresponding dentry.
* The dentry may or may not be connected to the filesystem root.
*/
static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
int fh_len, int fh_type)
{
return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
fat_nfs_get_inode);
}
static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb,
struct fid *fh, int fh_len,
int fh_type)
{
struct inode *inode = NULL;
struct fat_fid *fid = (struct fat_fid *)fh;
loff_t i_pos;
switch (fh_type) {
case FILEID_FAT_WITHOUT_PARENT:
if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT)
return NULL;
break;
case FILEID_FAT_WITH_PARENT:
if (fh_len < FAT_FID_SIZE_WITH_PARENT)
return NULL;
break;
default:
return NULL;
}
i_pos = fid->i_pos_hi;
i_pos = (i_pos << 32) | (fid->i_pos_low);
inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos);
return d_obtain_alias(inode);
}
/*
* Find the parent for a file specified by NFS handle.
* This requires that the handle contain the i_ino of the parent.
*/
static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
int fh_len, int fh_type)
{
return generic_fh_to_parent(sb, fid, fh_len, fh_type,
fat_nfs_get_inode);
}
static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
struct fid *fh, int fh_len,
int fh_type)
{
struct inode *inode = NULL;
struct fat_fid *fid = (struct fat_fid *)fh;
loff_t i_pos;
if (fh_len < FAT_FID_SIZE_WITH_PARENT)
return NULL;
switch (fh_type) {
case FILEID_FAT_WITH_PARENT:
i_pos = fid->parent_i_pos_hi;
i_pos = (i_pos << 32) | (fid->parent_i_pos_low);
inode = __fat_nfs_get_inode(sb, 0, fid->parent_i_gen, i_pos);
break;
}
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.
*/
static 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;
struct inode *parent_inode = NULL;
if (!fat_get_dotdot_entry(child_dir->d_inode, &bh, &de)) {
int parent_logstart = fat_get_start(MSDOS_SB(sb), de);
parent_inode = fat_dget(sb, parent_logstart);
}
brelse(bh);
return d_obtain_alias(parent_inode);
}
const struct export_operations fat_export_ops = {
.fh_to_dentry = fat_fh_to_dentry,
.fh_to_parent = fat_fh_to_parent,
.get_parent = fat_get_parent,
};
const struct export_operations fat_export_ops_nostale = {
.encode_fh = fat_encode_fh_nostale,
.fh_to_dentry = fat_fh_to_dentry_nostale,
.fh_to_parent = fat_fh_to_parent_nostale,
.get_parent = fat_get_parent,
};
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