489 lines
12 KiB
C
489 lines
12 KiB
C
/*
|
|
* Copyright (C) Neil Brown 2002
|
|
* Copyright (C) Christoph Hellwig 2007
|
|
*
|
|
* This file contains the code mapping from inodes to NFS file handles,
|
|
* and for mapping back from file handles to dentries.
|
|
*
|
|
* For details on why we do all the strange and hairy things in here
|
|
* take a look at Documentation/filesystems/Exporting.
|
|
*/
|
|
#include <linux/exportfs.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/file.h>
|
|
#include <linux/module.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/namei.h>
|
|
#include <linux/sched.h>
|
|
|
|
#define dprintk(fmt, args...) do{}while(0)
|
|
|
|
|
|
static int get_name(struct vfsmount *mnt, struct dentry *dentry, char *name,
|
|
struct dentry *child);
|
|
|
|
|
|
static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir,
|
|
char *name, struct dentry *child)
|
|
{
|
|
const struct export_operations *nop = dir->d_sb->s_export_op;
|
|
|
|
if (nop->get_name)
|
|
return nop->get_name(dir, name, child);
|
|
else
|
|
return get_name(mnt, dir, name, child);
|
|
}
|
|
|
|
/*
|
|
* Check if the dentry or any of it's aliases is acceptable.
|
|
*/
|
|
static struct dentry *
|
|
find_acceptable_alias(struct dentry *result,
|
|
int (*acceptable)(void *context, struct dentry *dentry),
|
|
void *context)
|
|
{
|
|
struct dentry *dentry, *toput = NULL;
|
|
|
|
if (acceptable(context, result))
|
|
return result;
|
|
|
|
spin_lock(&dcache_lock);
|
|
list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
|
|
dget_locked(dentry);
|
|
spin_unlock(&dcache_lock);
|
|
if (toput)
|
|
dput(toput);
|
|
if (dentry != result && acceptable(context, dentry)) {
|
|
dput(result);
|
|
return dentry;
|
|
}
|
|
spin_lock(&dcache_lock);
|
|
toput = dentry;
|
|
}
|
|
spin_unlock(&dcache_lock);
|
|
|
|
if (toput)
|
|
dput(toput);
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Find root of a disconnected subtree and return a reference to it.
|
|
*/
|
|
static struct dentry *
|
|
find_disconnected_root(struct dentry *dentry)
|
|
{
|
|
dget(dentry);
|
|
spin_lock(&dentry->d_lock);
|
|
while (!IS_ROOT(dentry) &&
|
|
(dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
|
|
struct dentry *parent = dentry->d_parent;
|
|
dget(parent);
|
|
spin_unlock(&dentry->d_lock);
|
|
dput(dentry);
|
|
dentry = parent;
|
|
spin_lock(&dentry->d_lock);
|
|
}
|
|
spin_unlock(&dentry->d_lock);
|
|
return dentry;
|
|
}
|
|
|
|
|
|
/*
|
|
* Make sure target_dir is fully connected to the dentry tree.
|
|
*
|
|
* It may already be, as the flag isn't always updated when connection happens.
|
|
*/
|
|
static int
|
|
reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
|
|
{
|
|
int noprogress = 0;
|
|
int err = -ESTALE;
|
|
|
|
/*
|
|
* It is possible that a confused file system might not let us complete
|
|
* the path to the root. For example, if get_parent returns a directory
|
|
* in which we cannot find a name for the child. While this implies a
|
|
* very sick filesystem we don't want it to cause knfsd to spin. Hence
|
|
* the noprogress counter. If we go through the loop 10 times (2 is
|
|
* probably enough) without getting anywhere, we just give up
|
|
*/
|
|
while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
|
|
struct dentry *pd = find_disconnected_root(target_dir);
|
|
|
|
if (!IS_ROOT(pd)) {
|
|
/* must have found a connected parent - great */
|
|
spin_lock(&pd->d_lock);
|
|
pd->d_flags &= ~DCACHE_DISCONNECTED;
|
|
spin_unlock(&pd->d_lock);
|
|
noprogress = 0;
|
|
} else if (pd == mnt->mnt_sb->s_root) {
|
|
printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
|
|
spin_lock(&pd->d_lock);
|
|
pd->d_flags &= ~DCACHE_DISCONNECTED;
|
|
spin_unlock(&pd->d_lock);
|
|
noprogress = 0;
|
|
} else {
|
|
/*
|
|
* We have hit the top of a disconnected path, try to
|
|
* find parent and connect.
|
|
*
|
|
* Racing with some other process renaming a directory
|
|
* isn't much of a problem here. If someone renames
|
|
* the directory, it will end up properly connected,
|
|
* which is what we want
|
|
*
|
|
* Getting the parent can't be supported generically,
|
|
* the locking is too icky.
|
|
*
|
|
* Instead we just return EACCES. If server reboots
|
|
* or inodes get flushed, you lose
|
|
*/
|
|
struct dentry *ppd = ERR_PTR(-EACCES);
|
|
struct dentry *npd;
|
|
|
|
mutex_lock(&pd->d_inode->i_mutex);
|
|
if (mnt->mnt_sb->s_export_op->get_parent)
|
|
ppd = mnt->mnt_sb->s_export_op->get_parent(pd);
|
|
mutex_unlock(&pd->d_inode->i_mutex);
|
|
|
|
if (IS_ERR(ppd)) {
|
|
err = PTR_ERR(ppd);
|
|
dprintk("%s: get_parent of %ld failed, err %d\n",
|
|
__func__, pd->d_inode->i_ino, err);
|
|
dput(pd);
|
|
break;
|
|
}
|
|
|
|
dprintk("%s: find name of %lu in %lu\n", __func__,
|
|
pd->d_inode->i_ino, ppd->d_inode->i_ino);
|
|
err = exportfs_get_name(mnt, ppd, nbuf, pd);
|
|
if (err) {
|
|
dput(ppd);
|
|
dput(pd);
|
|
if (err == -ENOENT)
|
|
/* some race between get_parent and
|
|
* get_name? just try again
|
|
*/
|
|
continue;
|
|
break;
|
|
}
|
|
dprintk("%s: found name: %s\n", __func__, nbuf);
|
|
mutex_lock(&ppd->d_inode->i_mutex);
|
|
npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
|
|
mutex_unlock(&ppd->d_inode->i_mutex);
|
|
if (IS_ERR(npd)) {
|
|
err = PTR_ERR(npd);
|
|
dprintk("%s: lookup failed: %d\n",
|
|
__func__, err);
|
|
dput(ppd);
|
|
dput(pd);
|
|
break;
|
|
}
|
|
/* we didn't really want npd, we really wanted
|
|
* a side-effect of the lookup.
|
|
* hopefully, npd == pd, though it isn't really
|
|
* a problem if it isn't
|
|
*/
|
|
if (npd == pd)
|
|
noprogress = 0;
|
|
else
|
|
printk("%s: npd != pd\n", __func__);
|
|
dput(npd);
|
|
dput(ppd);
|
|
if (IS_ROOT(pd)) {
|
|
/* something went wrong, we have to give up */
|
|
dput(pd);
|
|
break;
|
|
}
|
|
}
|
|
dput(pd);
|
|
}
|
|
|
|
if (target_dir->d_flags & DCACHE_DISCONNECTED) {
|
|
/* something went wrong - oh-well */
|
|
if (!err)
|
|
err = -ESTALE;
|
|
return err;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
struct getdents_callback {
|
|
char *name; /* name that was found. It already points to a
|
|
buffer NAME_MAX+1 is size */
|
|
unsigned long ino; /* the inum we are looking for */
|
|
int found; /* inode matched? */
|
|
int sequence; /* sequence counter */
|
|
};
|
|
|
|
/*
|
|
* A rather strange filldir function to capture
|
|
* the name matching the specified inode number.
|
|
*/
|
|
static int filldir_one(void * __buf, const char * name, int len,
|
|
loff_t pos, u64 ino, unsigned int d_type)
|
|
{
|
|
struct getdents_callback *buf = __buf;
|
|
int result = 0;
|
|
|
|
buf->sequence++;
|
|
if (buf->ino == ino) {
|
|
memcpy(buf->name, name, len);
|
|
buf->name[len] = '\0';
|
|
buf->found = 1;
|
|
result = -1;
|
|
}
|
|
return result;
|
|
}
|
|
|
|
/**
|
|
* get_name - default export_operations->get_name function
|
|
* @dentry: the directory in which to find a name
|
|
* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
|
|
* @child: the dentry for the child directory.
|
|
*
|
|
* calls readdir on the parent until it finds an entry with
|
|
* the same inode number as the child, and returns that.
|
|
*/
|
|
static int get_name(struct vfsmount *mnt, struct dentry *dentry,
|
|
char *name, struct dentry *child)
|
|
{
|
|
const struct cred *cred = current_cred();
|
|
struct inode *dir = dentry->d_inode;
|
|
int error;
|
|
struct file *file;
|
|
struct getdents_callback buffer;
|
|
|
|
error = -ENOTDIR;
|
|
if (!dir || !S_ISDIR(dir->i_mode))
|
|
goto out;
|
|
error = -EINVAL;
|
|
if (!dir->i_fop)
|
|
goto out;
|
|
/*
|
|
* Open the directory ...
|
|
*/
|
|
file = dentry_open(dget(dentry), mntget(mnt), O_RDONLY, cred);
|
|
error = PTR_ERR(file);
|
|
if (IS_ERR(file))
|
|
goto out;
|
|
|
|
error = -EINVAL;
|
|
if (!file->f_op->readdir)
|
|
goto out_close;
|
|
|
|
buffer.name = name;
|
|
buffer.ino = child->d_inode->i_ino;
|
|
buffer.found = 0;
|
|
buffer.sequence = 0;
|
|
while (1) {
|
|
int old_seq = buffer.sequence;
|
|
|
|
error = vfs_readdir(file, filldir_one, &buffer);
|
|
if (buffer.found) {
|
|
error = 0;
|
|
break;
|
|
}
|
|
|
|
if (error < 0)
|
|
break;
|
|
|
|
error = -ENOENT;
|
|
if (old_seq == buffer.sequence)
|
|
break;
|
|
}
|
|
|
|
out_close:
|
|
fput(file);
|
|
out:
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* export_encode_fh - default export_operations->encode_fh function
|
|
* @dentry: the dentry to encode
|
|
* @fh: where to store the file handle fragment
|
|
* @max_len: maximum length to store there
|
|
* @connectable: whether to store parent information
|
|
*
|
|
* This default encode_fh function assumes that the 32 inode number
|
|
* is suitable for locating an inode, and that the generation number
|
|
* can be used to check that it is still valid. It places them in the
|
|
* filehandle fragment where export_decode_fh expects to find them.
|
|
*/
|
|
static int export_encode_fh(struct dentry *dentry, struct fid *fid,
|
|
int *max_len, int connectable)
|
|
{
|
|
struct inode * inode = dentry->d_inode;
|
|
int len = *max_len;
|
|
int type = FILEID_INO32_GEN;
|
|
|
|
if (len < 2 || (connectable && len < 4))
|
|
return 255;
|
|
|
|
len = 2;
|
|
fid->i32.ino = inode->i_ino;
|
|
fid->i32.gen = inode->i_generation;
|
|
if (connectable && !S_ISDIR(inode->i_mode)) {
|
|
struct inode *parent;
|
|
|
|
spin_lock(&dentry->d_lock);
|
|
parent = dentry->d_parent->d_inode;
|
|
fid->i32.parent_ino = parent->i_ino;
|
|
fid->i32.parent_gen = parent->i_generation;
|
|
spin_unlock(&dentry->d_lock);
|
|
len = 4;
|
|
type = FILEID_INO32_GEN_PARENT;
|
|
}
|
|
*max_len = len;
|
|
return type;
|
|
}
|
|
|
|
int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
|
|
int connectable)
|
|
{
|
|
const struct export_operations *nop = dentry->d_sb->s_export_op;
|
|
int error;
|
|
|
|
if (nop->encode_fh)
|
|
error = nop->encode_fh(dentry, fid->raw, max_len, connectable);
|
|
else
|
|
error = export_encode_fh(dentry, fid, max_len, connectable);
|
|
|
|
return error;
|
|
}
|
|
EXPORT_SYMBOL_GPL(exportfs_encode_fh);
|
|
|
|
struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
|
|
int fh_len, int fileid_type,
|
|
int (*acceptable)(void *, struct dentry *), void *context)
|
|
{
|
|
const struct export_operations *nop = mnt->mnt_sb->s_export_op;
|
|
struct dentry *result, *alias;
|
|
char nbuf[NAME_MAX+1];
|
|
int err;
|
|
|
|
/*
|
|
* Try to get any dentry for the given file handle from the filesystem.
|
|
*/
|
|
result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
|
|
if (!result)
|
|
result = ERR_PTR(-ESTALE);
|
|
if (IS_ERR(result))
|
|
return result;
|
|
|
|
if (S_ISDIR(result->d_inode->i_mode)) {
|
|
/*
|
|
* This request is for a directory.
|
|
*
|
|
* On the positive side there is only one dentry for each
|
|
* directory inode. On the negative side this implies that we
|
|
* to ensure our dentry is connected all the way up to the
|
|
* filesystem root.
|
|
*/
|
|
if (result->d_flags & DCACHE_DISCONNECTED) {
|
|
err = reconnect_path(mnt, result, nbuf);
|
|
if (err)
|
|
goto err_result;
|
|
}
|
|
|
|
if (!acceptable(context, result)) {
|
|
err = -EACCES;
|
|
goto err_result;
|
|
}
|
|
|
|
return result;
|
|
} else {
|
|
/*
|
|
* It's not a directory. Life is a little more complicated.
|
|
*/
|
|
struct dentry *target_dir, *nresult;
|
|
|
|
/*
|
|
* See if either the dentry we just got from the filesystem
|
|
* or any alias for it is acceptable. This is always true
|
|
* if this filesystem is exported without the subtreecheck
|
|
* option. If the filesystem is exported with the subtree
|
|
* check option there's a fair chance we need to look at
|
|
* the parent directory in the file handle and make sure
|
|
* it's connected to the filesystem root.
|
|
*/
|
|
alias = find_acceptable_alias(result, acceptable, context);
|
|
if (alias)
|
|
return alias;
|
|
|
|
/*
|
|
* Try to extract a dentry for the parent directory from the
|
|
* file handle. If this fails we'll have to give up.
|
|
*/
|
|
err = -ESTALE;
|
|
if (!nop->fh_to_parent)
|
|
goto err_result;
|
|
|
|
target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
|
|
fh_len, fileid_type);
|
|
if (!target_dir)
|
|
goto err_result;
|
|
err = PTR_ERR(target_dir);
|
|
if (IS_ERR(target_dir))
|
|
goto err_result;
|
|
|
|
/*
|
|
* And as usual we need to make sure the parent directory is
|
|
* connected to the filesystem root. The VFS really doesn't
|
|
* like disconnected directories..
|
|
*/
|
|
err = reconnect_path(mnt, target_dir, nbuf);
|
|
if (err) {
|
|
dput(target_dir);
|
|
goto err_result;
|
|
}
|
|
|
|
/*
|
|
* Now that we've got both a well-connected parent and a
|
|
* dentry for the inode we're after, make sure that our
|
|
* inode is actually connected to the parent.
|
|
*/
|
|
err = exportfs_get_name(mnt, target_dir, nbuf, result);
|
|
if (!err) {
|
|
mutex_lock(&target_dir->d_inode->i_mutex);
|
|
nresult = lookup_one_len(nbuf, target_dir,
|
|
strlen(nbuf));
|
|
mutex_unlock(&target_dir->d_inode->i_mutex);
|
|
if (!IS_ERR(nresult)) {
|
|
if (nresult->d_inode) {
|
|
dput(result);
|
|
result = nresult;
|
|
} else
|
|
dput(nresult);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* At this point we are done with the parent, but it's pinned
|
|
* by the child dentry anyway.
|
|
*/
|
|
dput(target_dir);
|
|
|
|
/*
|
|
* And finally make sure the dentry is actually acceptable
|
|
* to NFSD.
|
|
*/
|
|
alias = find_acceptable_alias(result, acceptable, context);
|
|
if (!alias) {
|
|
err = -EACCES;
|
|
goto err_result;
|
|
}
|
|
|
|
return alias;
|
|
}
|
|
|
|
err_result:
|
|
dput(result);
|
|
return ERR_PTR(err);
|
|
}
|
|
EXPORT_SYMBOL_GPL(exportfs_decode_fh);
|
|
|
|
MODULE_LICENSE("GPL");
|