NFS: Allow concurrent inode revalidation

Currently, if two processes are both trying to revalidate metadata for the
same inode, they will find themselves being serialised. There is no good
justification for this now that we have improved our ability to detect
stale attribute data, so we should remove that serialisation.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/inode.c

@@ -472,37 +472,6 @@ void nfs_setattr_update_inode(struct inode *inode, struct iattr *attr)
 	}
 }
 
-static int nfs_wait_schedule(void *word)
-{
-	if (signal_pending(current))
-		return -ERESTARTSYS;
-	schedule();
-	return 0;
-}
-
-/*
- * Wait for the inode to get unlocked.
- */
-static int nfs_wait_on_inode(struct inode *inode)
-{
-	struct nfs_inode *nfsi = NFS_I(inode);
-	int error;
-
-	error = wait_on_bit_lock(&nfsi->flags, NFS_INO_REVALIDATING,
-					nfs_wait_schedule, TASK_KILLABLE);
-
-	return error;
-}
-
-static void nfs_wake_up_inode(struct inode *inode)
-{
-	struct nfs_inode *nfsi = NFS_I(inode);
-
-	clear_bit(NFS_INO_REVALIDATING, &nfsi->flags);
-	smp_mb__after_clear_bit();
-	wake_up_bit(&nfsi->flags, NFS_INO_REVALIDATING);
-}
-
 int nfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 {
 	struct inode *inode = dentry->d_inode;
@@ -697,20 +666,15 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 	dfprintk(PAGECACHE, "NFS: revalidating (%s/%Ld)\n",
 		inode->i_sb->s_id, (long long)NFS_FILEID(inode));
 
-	nfs_inc_stats(inode, NFSIOS_INODEREVALIDATE);
 	if (is_bad_inode(inode))
- 		goto out_nowait;
+		goto out;
 	if (NFS_STALE(inode))
- 		goto out_nowait;
-
-	status = nfs_wait_on_inode(inode);
-	if (status < 0)
 		goto out;
 
-	status = -ESTALE;
 	if (NFS_STALE(inode))
 		goto out;
 
+	nfs_inc_stats(inode, NFSIOS_INODEREVALIDATE);
 	status = NFS_PROTO(inode)->getattr(server, NFS_FH(inode), &fattr);
 	if (status != 0) {
 		dfprintk(PAGECACHE, "nfs_revalidate_inode: (%s/%Ld) getattr failed, error=%d\n",
@@ -740,9 +704,6 @@ __nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 		(long long)NFS_FILEID(inode));
 
  out:
-	nfs_wake_up_inode(inode);
-
- out_nowait:
 	return status;
 }
 

include/linux/nfs_fs.h

@@ -200,11 +200,10 @@ struct nfs_inode {
 /*
  * Bit offsets in flags field
  */
-#define NFS_INO_REVALIDATING	(0)		/* revalidating attrs */
-#define NFS_INO_ADVISE_RDPLUS	(1)		/* advise readdirplus */
-#define NFS_INO_STALE		(2)		/* possible stale inode */
-#define NFS_INO_ACL_LRU_SET	(3)		/* Inode is on the LRU list */
-#define NFS_INO_MOUNTPOINT	(4)		/* inode is remote mountpoint */
+#define NFS_INO_ADVISE_RDPLUS	(0)		/* advise readdirplus */
+#define NFS_INO_STALE		(1)		/* possible stale inode */
+#define NFS_INO_ACL_LRU_SET	(2)		/* Inode is on the LRU list */
+#define NFS_INO_MOUNTPOINT	(3)		/* inode is remote mountpoint */
 
 static inline struct nfs_inode *NFS_I(const struct inode *inode)
 {