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/*
* Overlayfs NFS export support.
*
* Amir Goldstein <amir73il@gmail.com>
*
* Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*/
#include <linux/fs.h>
#include <linux/cred.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/exportfs.h>
#include <linux/ratelimit.h>
#include "overlayfs.h"
static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen)
{
struct dentry *upper = ovl_dentry_upper(dentry);
struct dentry *origin = ovl_dentry_lower(dentry);
struct ovl_fh *fh = NULL;
int err;
/*
* On overlay with an upper layer, overlay root inode is encoded as
* an upper file handle, because upper root dir is not indexed.
*/
if (dentry == dentry->d_sb->s_root && upper)
origin = NULL;
err = -EACCES;
if (!upper || origin)
goto fail;
/* TODO: encode non pure-upper by origin */
fh = ovl_encode_fh(upper, true);
err = -EOVERFLOW;
if (fh->len > buflen)
goto fail;
memcpy(buf, (char *)fh, fh->len);
err = fh->len;
out:
kfree(fh);
return err;
fail:
pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n",
dentry, err, buflen, fh ? (int)fh->len : 0,
fh ? fh->type : 0);
goto out;
}
static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len)
{
int res, len = *max_len << 2;
res = ovl_d_to_fh(dentry, (char *)fid, len);
if (res <= 0)
return FILEID_INVALID;
len = res;
/* Round up to dwords */
*max_len = (len + 3) >> 2;
return OVL_FILEID;
}
static int ovl_encode_inode_fh(struct inode *inode, u32 *fid, int *max_len,
struct inode *parent)
{
struct dentry *dentry;
int type;
/* TODO: encode connectable file handles */
if (parent)
return FILEID_INVALID;
dentry = d_find_any_alias(inode);
if (WARN_ON(!dentry))
return FILEID_INVALID;
type = ovl_dentry_to_fh(dentry, fid, max_len);
dput(dentry);
return type;
}
/*
* Find or instantiate an overlay dentry from real dentries.
*/
static struct dentry *ovl_obtain_alias(struct super_block *sb,
struct dentry *upper,
struct ovl_path *lowerpath)
{
struct inode *inode;
struct dentry *dentry;
struct ovl_entry *oe;
void *fsdata = &oe;
/* TODO: obtain non pure-upper */
if (lowerpath)
return ERR_PTR(-EIO);
inode = ovl_get_inode(sb, dget(upper), NULL, NULL, 0);
if (IS_ERR(inode)) {
dput(upper);
return ERR_CAST(inode);
}
dentry = d_find_any_alias(inode);
if (!dentry) {
dentry = d_alloc_anon(inode->i_sb);
if (!dentry)
goto nomem;
oe = ovl_alloc_entry(0);
if (!oe)
goto nomem;
dentry->d_fsdata = oe;
ovl_dentry_set_upper_alias(dentry);
}
return d_instantiate_anon(dentry, inode);
nomem:
iput(inode);
dput(dentry);
return ERR_PTR(-ENOMEM);
}
static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
struct ovl_fh *fh)
{
struct ovl_fs *ofs = sb->s_fs_info;
struct dentry *dentry;
struct dentry *upper;
if (!ofs->upper_mnt)
return ERR_PTR(-EACCES);
upper = ovl_decode_fh(fh, ofs->upper_mnt);
if (IS_ERR_OR_NULL(upper))
return upper;
dentry = ovl_obtain_alias(sb, upper, NULL);
dput(upper);
return dentry;
}
static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid,
int fh_len, int fh_type)
{
struct dentry *dentry = NULL;
struct ovl_fh *fh = (struct ovl_fh *) fid;
int len = fh_len << 2;
unsigned int flags = 0;
int err;
err = -EINVAL;
if (fh_type != OVL_FILEID)
goto out_err;
err = ovl_check_fh_len(fh, len);
if (err)
goto out_err;
/* TODO: decode non-upper */
flags = fh->flags;
if (flags & OVL_FH_FLAG_PATH_UPPER)
dentry = ovl_upper_fh_to_d(sb, fh);
err = PTR_ERR(dentry);
if (IS_ERR(dentry) && err != -ESTALE)
goto out_err;
return dentry;
out_err:
pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n",
len, fh_type, flags, err);
return ERR_PTR(err);
}
const struct export_operations ovl_export_operations = {
.encode_fh = ovl_encode_inode_fh,
.fh_to_dentry = ovl_fh_to_dentry,
};
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