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nfs: use change attribute for NFS re-exports 

When exporting NFS, we may as well use the real change attribute
returned by the original server instead of faking up a change attribute
from the ctime.

Note we can't do that by setting I_VERSION--that would also turn on the
logic in iversion.h which treats the lower bit specially, and that
doesn't make sense for NFS.

So instead we define a new export operation for filesystems like NFS
that want to manage the change attribute themselves.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
J. Bruce Fields 2021-01-29 14:26:29 -05:00 committed by Chuck Lever
parent 02591f9feb
commit 3cc55f4434
3 changed files with 23 additions and 1 deletions
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18
fs/nfs/export.c
View File

@ -167,10 +167,28 @@ out:
return parent;
}
static u64 nfs_fetch_iversion(struct inode *inode)
{
struct nfs_server *server = NFS_SERVER(inode);
/* Is this the right call?: */
nfs_revalidate_inode(server, inode);
/*
* Also, note we're ignoring any returned error. That seems to be
* the practice for cache consistency information elsewhere in
* the server, but I'm not sure why.
*/
if (server->nfs_client->rpc_ops->version >= 4)
return inode_peek_iversion_raw(inode);
else
return time_to_chattr(&inode->i_ctime);
}
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,

5
fs/nfsd/nfsfh.h
View File

@ -12,6 +12,7 @@
#include <linux/sunrpc/svc.h>
#include <uapi/linux/nfsd/nfsfh.h>
#include <linux/iversion.h>
#include <linux/exportfs.h>
static inline __u32 ino_t_to_u32(ino_t ino)
{
@ -264,7 +265,9 @@ fh_clear_wcc(struct svc_fh *fhp)
static inline u64 nfsd4_change_attribute(struct kstat *stat,
struct inode *inode)
{
if (IS_I_VERSION(inode)) {
if (inode->i_sb->s_export_op->fetch_iversion)
return inode->i_sb->s_export_op->fetch_iversion(inode);
else if (IS_I_VERSION(inode)) {
u64 chattr;
chattr = stat->ctime.tv_sec;

1
include/linux/exportfs.h
View File

@ -213,6 +213,7 @@ struct export_operations {
bool write, u32 *device_generation);
int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
int nr_iomaps, struct iattr *iattr);
u64 (*fetch_iversion)(struct inode *);
#define EXPORT_OP_NOWCC (0x1) /* don't collect v3 wcc data */
#define EXPORT_OP_NOSUBTREECHK (0x2) /* no subtree checking */
#define EXPORT_OP_CLOSE_BEFORE_UNLINK (0x4) /* close files before unlink */