Re: [PATCH] Reinstantiating stale inodes

[Steve Dickson <SteveD@redhat.com>]

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Trond Myklebust wrote:

>You can if and only if
>
>  - The dentry is unhashed, and you are holding the semaphore dir->i_sem
>on the parent directory.
>OR
>  - You are holding the spin lock dcache_lock.
>  
>
I decide to hold the dir->i_sem semaphore since d_drop() needs the
dcache_lock to do the unhashing...

>Note: on 2.6.x, the second condition needs to be modified a bit: you
>probably need to hold dentry->d_lock too since the 2.6.x version of
>d_lookup() is by and large lockless...
>  
>
I'll take a look asaic...

SteveD.

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--- linux-2.4.21/fs/nfs/inode.c.org	2004-04-17 18:26:32.000000000 -0400
+++ linux-2.4.21/fs/nfs/inode.c	2004-04-23 14:44:59.000000000 -0400
@@ -953,13 +953,74 @@ nfs_wait_on_inode(struct inode *inode, i
 }
 
 /*
+ * Reinstantiate an inode that has gone stale
+ */
+static int
+nfs_reinstantiate(
+	struct inode *dir, 
+	struct dentry *dentry, 
+	struct nfs_fattr *fattr)
+{
+	int error;
+	struct nfs_fh fhandle;
+	struct inode *inode;
+
+	/*
+	 * We can only reinstantiate the inode if we are the
+	 * only ones accessing it.
+	 */
+	if (atomic_read(&dentry->d_count) > 1)
+		return EACCES;
+
+	error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, &fhandle, &fattr);
+	if (!error) {
+		error = -ENOMEM;
+		inode = nfs_fhget(dentry, &fhandle, &fattr);
+		if (inode) {
+			/*
+			 * Check again this time holding the i_sem semaphore
+			 * to make sure we are the only ones accessing this
+			 * dentry
+			 */
+			down(&dir->i_sem);
+			if (atomic_read(&dentry->d_count) < 2) {
+				d_drop(dentry);
+				dput(dentry);
+				d_instantiate(dentry, inode);
+				dentry->d_time = jiffies;
+				error = 0;
+			} else
+				iput(inode);
+			up(&dir->i_sem);
+		}
+	}
+	return error;
+}
+
+/*
  * Externally visible revalidation function
  */
 int
 nfs_revalidate(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
-	return nfs_revalidate_inode(NFS_SERVER(inode), inode);
+	struct inode *pinode;
+	struct nfs_fattr fattr;
+	int error;
+
+	error = nfs_revalidate_inode(NFS_SERVER(inode), inode);
+	if (!error || error != -ESTALE)
+		return error;
+	/*
+	 * We have a stale fh so ask the server for another one
+	 */
+	pinode = dentry->d_parent->d_inode;	
+	if (nfs_reinstantiate(pinode, dentry, &fattr) == 0) {
+		inode = dentry->d_inode;
+		if (nfs_refresh_inode(inode, &fattr) == 0)
+			error = 0;
+	}
+	return error;
 }
 
 /*