original development tree for Linux kernel GTP module; now long in mainline.
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/*
* fs/isofs/export.c
*
* (C) 2004 Paul Serice - The new inode scheme requires switching
* from iget() to iget5_locked() which means
* the NFS export operations have to be hand
* coded because the default routines rely on
* iget().
*
* The following files are helpful:
*
* Documentation/filesystems/nfs/Exporting
* fs/exportfs/expfs.c.
*/
#include "isofs.h"
static struct dentry *
isofs_export_iget(struct super_block *sb,
unsigned long block,
unsigned long offset,
__u32 generation)
{
struct inode *inode;
if (block == 0)
return ERR_PTR(-ESTALE);
inode = isofs_iget(sb, block, offset);
if (IS_ERR(inode))
return ERR_CAST(inode);
if (generation && inode->i_generation != generation) {
iput(inode);
return ERR_PTR(-ESTALE);
}
return d_obtain_alias(inode);
}
/* This function is surprisingly simple. The trick is understanding
* that "child" is always a directory. So, to find its parent, you
* simply need to find its ".." entry, normalize its block and offset,
* and return the underlying inode. See the comments for
* isofs_normalize_block_and_offset(). */
static struct dentry *isofs_export_get_parent(struct dentry *child)
{
unsigned long parent_block = 0;
unsigned long parent_offset = 0;
struct inode *child_inode = child->d_inode;
struct iso_inode_info *e_child_inode = ISOFS_I(child_inode);
struct iso_directory_record *de = NULL;
struct buffer_head * bh = NULL;
struct dentry *rv = NULL;
/* "child" must always be a directory. */
if (!S_ISDIR(child_inode->i_mode)) {
printk(KERN_ERR "isofs: isofs_export_get_parent(): "
"child is not a directory!\n");
rv = ERR_PTR(-EACCES);
goto out;
}
/* It is an invariant that the directory offset is zero. If
* it is not zero, it means the directory failed to be
* normalized for some reason. */
if (e_child_inode->i_iget5_offset != 0) {
printk(KERN_ERR "isofs: isofs_export_get_parent(): "
"child directory not normalized!\n");
rv = ERR_PTR(-EACCES);
goto out;
}
/* The child inode has been normalized such that its
* i_iget5_block value points to the "." entry. Fortunately,
* the ".." entry is located in the same block. */
parent_block = e_child_inode->i_iget5_block;
/* Get the block in question. */
bh = sb_bread(child_inode->i_sb, parent_block);
if (bh == NULL) {
rv = ERR_PTR(-EACCES);
goto out;
}
/* This is the "." entry. */
de = (struct iso_directory_record*)bh->b_data;
/* The ".." entry is always the second entry. */
parent_offset = (unsigned long)isonum_711(de->length);
de = (struct iso_directory_record*)(bh->b_data + parent_offset);
/* Verify it is in fact the ".." entry. */
if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) {
printk(KERN_ERR "isofs: Unable to find the \"..\" "
"directory for NFS.\n");
rv = ERR_PTR(-EACCES);
goto out;
}
/* Normalize */
isofs_normalize_block_and_offset(de, &parent_block, &parent_offset);
rv = d_obtain_alias(isofs_iget(child_inode->i_sb, parent_block,
parent_offset));
out:
if (bh)
brelse(bh);
return rv;
}
static int
isofs_export_encode_fh(struct inode *inode,
__u32 *fh32,
int *max_len,
struct inode *parent)
{
struct iso_inode_info * ei = ISOFS_I(inode);
int len = *max_len;
int type = 1;
__u16 *fh16 = (__u16*)fh32;
/*
* WARNING: max_len is 5 for NFSv2. Because of this
* limitation, we use the lower 16 bits of fh32[1] to hold the
* offset of the inode and the upper 16 bits of fh32[1] to
* hold the offset of the parent.
*/
if (parent && (len < 5)) {
*max_len = 5;
return FILEID_INVALID;
} else if (len < 3) {
*max_len = 3;
return FILEID_INVALID;
}
len = 3;
fh32[0] = ei->i_iget5_block;
fh16[2] = (__u16)ei->i_iget5_offset; /* fh16 [sic] */
fh16[3] = 0; /* avoid leaking uninitialized data */
fh32[2] = inode->i_generation;
if (parent) {
struct iso_inode_info *eparent;
eparent = ISOFS_I(parent);
fh32[3] = eparent->i_iget5_block;
fh16[3] = (__u16)eparent->i_iget5_offset; /* fh16 [sic] */
fh32[4] = parent->i_generation;
len = 5;
type = 2;
}
*max_len = len;
return type;
}
struct isofs_fid {
u32 block;
u16 offset;
u16 parent_offset;
u32 generation;
u32 parent_block;
u32 parent_generation;
};
static struct dentry *isofs_fh_to_dentry(struct super_block *sb,
struct fid *fid, int fh_len, int fh_type)
{
struct isofs_fid *ifid = (struct isofs_fid *)fid;
if (fh_len < 3 || fh_type > 2)
return NULL;
return isofs_export_iget(sb, ifid->block, ifid->offset,
ifid->generation);
}
static struct dentry *isofs_fh_to_parent(struct super_block *sb,
struct fid *fid, int fh_len, int fh_type)
{
struct isofs_fid *ifid = (struct isofs_fid *)fid;
if (fh_len < 2 || fh_type != 2)
return NULL;
return isofs_export_iget(sb,
fh_len > 2 ? ifid->parent_block : 0,
ifid->parent_offset,
fh_len > 4 ? ifid->parent_generation : 0);
}
const struct export_operations isofs_export_ops = {
.encode_fh = isofs_export_encode_fh,
.fh_to_dentry = isofs_fh_to_dentry,
.fh_to_parent = isofs_fh_to_parent,
.get_parent = isofs_export_get_parent,
};