linux/fs/nfs/export.c
J. Bruce Fields 40595cdc93 nfs: block notification on fs with its own ->lock
NFSv4.1 supports an optional lock notification feature which notifies
the client when a lock comes available.  (Normally NFSv4 clients just
poll for locks if necessary.)  To make that work, we need to request a
blocking lock from the filesystem.

We turned that off for NFS in commit f657f8eef3 ("nfs: don't atempt
blocking locks on nfs reexports") [sic] because it actually blocks the
nfsd thread while waiting for the lock.

Thanks to Vasily Averin for pointing out that NFS isn't the only
filesystem with that problem.

Any filesystem that leaves ->lock NULL will use posix_lock_file(), which
does the right thing.  Simplest is just to assume that any filesystem
that defines its own ->lock is not safe to request a blocking lock from.

So, this patch mostly reverts commit f657f8eef3 ("nfs: don't atempt
blocking locks on nfs reexports") [sic] and commit b840be2f00 ("lockd:
don't attempt blocking locks on nfs reexports"), and instead uses a
check of ->lock (Vasily's suggestion) to decide whether to support
blocking lock notifications on a given filesystem.  Also add a little
documentation.

Perhaps someday we could add back an export flag later to allow
filesystems with "good" ->lock methods to support blocking lock
notifications.

Reported-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
[ cel: Description rewritten to address checkpatch nits ]
[ cel: Fixed warning when SUNRPC debugging is disabled ]
[ cel: Fixed NULL check ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Vasily Averin <vvs@virtuozzo.com>
2022-01-08 14:42:01 -05:00

163 lines
4.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2015, Primary Data, Inc. All rights reserved.
*
* Tao Peng <bergwolf@primarydata.com>
*/
#include <linux/dcache.h>
#include <linux/exportfs.h>
#include <linux/nfs.h>
#include <linux/nfs_fs.h>
#include "internal.h"
#include "nfstrace.h"
#define NFSDBG_FACILITY NFSDBG_VFS
enum {
FILEID_HIGH_OFF = 0, /* inode fileid high */
FILEID_LOW_OFF, /* inode fileid low */
FILE_I_TYPE_OFF, /* inode type */
EMBED_FH_OFF /* embeded server fh */
};
static struct nfs_fh *nfs_exp_embedfh(__u32 *p)
{
return (struct nfs_fh *)(p + EMBED_FH_OFF);
}
/*
* Let's break subtree checking for now... otherwise we'll have to embed parent fh
* but there might not be enough space.
*/
static int
nfs_encode_fh(struct inode *inode, __u32 *p, int *max_len, struct inode *parent)
{
struct nfs_fh *server_fh = NFS_FH(inode);
struct nfs_fh *clnt_fh = nfs_exp_embedfh(p);
size_t fh_size = offsetof(struct nfs_fh, data) + server_fh->size;
int len = EMBED_FH_OFF + XDR_QUADLEN(fh_size);
dprintk("%s: max fh len %d inode %p parent %p",
__func__, *max_len, inode, parent);
if (*max_len < len || IS_AUTOMOUNT(inode)) {
dprintk("%s: fh len %d too small, required %d\n",
__func__, *max_len, len);
*max_len = len;
return FILEID_INVALID;
}
p[FILEID_HIGH_OFF] = NFS_FILEID(inode) >> 32;
p[FILEID_LOW_OFF] = NFS_FILEID(inode);
p[FILE_I_TYPE_OFF] = inode->i_mode & S_IFMT;
p[len - 1] = 0; /* Padding */
nfs_copy_fh(clnt_fh, server_fh);
*max_len = len;
dprintk("%s: result fh fileid %llu mode %u size %d\n",
__func__, NFS_FILEID(inode), inode->i_mode, *max_len);
return *max_len;
}
static struct dentry *
nfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
int fh_len, int fh_type)
{
struct nfs_fattr *fattr = NULL;
struct nfs_fh *server_fh = nfs_exp_embedfh(fid->raw);
size_t fh_size = offsetof(struct nfs_fh, data) + server_fh->size;
const struct nfs_rpc_ops *rpc_ops;
struct dentry *dentry;
struct inode *inode;
int len = EMBED_FH_OFF + XDR_QUADLEN(fh_size);
u32 *p = fid->raw;
int ret;
/* NULL translates to ESTALE */
if (fh_len < len || fh_type != len)
return NULL;
fattr = nfs_alloc_fattr_with_label(NFS_SB(sb));
if (fattr == NULL) {
dentry = ERR_PTR(-ENOMEM);
goto out;
}
fattr->fileid = ((u64)p[FILEID_HIGH_OFF] << 32) + p[FILEID_LOW_OFF];
fattr->mode = p[FILE_I_TYPE_OFF];
fattr->valid |= NFS_ATTR_FATTR_FILEID | NFS_ATTR_FATTR_TYPE;
dprintk("%s: fileid %llu mode %d\n", __func__, fattr->fileid, fattr->mode);
inode = nfs_ilookup(sb, fattr, server_fh);
if (inode)
goto out_found;
rpc_ops = NFS_SB(sb)->nfs_client->rpc_ops;
ret = rpc_ops->getattr(NFS_SB(sb), server_fh, fattr, NULL);
if (ret) {
dprintk("%s: getattr failed %d\n", __func__, ret);
trace_nfs_fh_to_dentry(sb, server_fh, fattr->fileid, ret);
dentry = ERR_PTR(ret);
goto out_free_fattr;
}
inode = nfs_fhget(sb, server_fh, fattr);
out_found:
dentry = d_obtain_alias(inode);
out_free_fattr:
nfs_free_fattr(fattr);
out:
return dentry;
}
static struct dentry *
nfs_get_parent(struct dentry *dentry)
{
int ret;
struct inode *inode = d_inode(dentry), *pinode;
struct super_block *sb = inode->i_sb;
struct nfs_server *server = NFS_SB(sb);
struct nfs_fattr *fattr = NULL;
struct dentry *parent;
struct nfs_rpc_ops const *ops = server->nfs_client->rpc_ops;
struct nfs_fh fh;
if (!ops->lookupp)
return ERR_PTR(-EACCES);
fattr = nfs_alloc_fattr_with_label(server);
if (fattr == NULL)
return ERR_PTR(-ENOMEM);
ret = ops->lookupp(inode, &fh, fattr);
if (ret) {
parent = ERR_PTR(ret);
goto out;
}
pinode = nfs_fhget(sb, &fh, fattr);
parent = d_obtain_alias(pinode);
out:
nfs_free_fattr(fattr);
return parent;
}
static u64 nfs_fetch_iversion(struct inode *inode)
{
nfs_revalidate_inode(inode, NFS_INO_INVALID_CHANGE);
return inode_peek_iversion_raw(inode);
}
const struct export_operations nfs_export_ops = {
.encode_fh = nfs_encode_fh,
.fh_to_dentry = nfs_fh_to_dentry,
.get_parent = nfs_get_parent,
.fetch_iversion = nfs_fetch_iversion,
.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|
EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS|
EXPORT_OP_NOATOMIC_ATTR,
};