From: Jeff Layton <jeff.layton@primarydata.com>
Date: Sun, 18 Aug 2019 14:18:44 -0400
Subject: sunrpc: add a new cache_detail operation for when a cache is flushed
Patch-mainline: v5.4-rc1
Git-commit: f69d6d8eef7807f8d937b81da24bebd2e926e4d2
References: bsc#1154353

When the exports table is changed, exportfs will usually write a new
time to the "flush" file in the nfsd.export cache procfile. This tells
the kernel to flush any entries that are older than that value.

This gives us a mechanism to tell whether an unexport might have
occurred. Add a new ->flush cache_detail operation that is called after
flushing the cache whenever someone writes to a "flush" file.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/linux/sunrpc/cache.h |    1 +
 net/sunrpc/cache.c           |    3 +++
 2 files changed, 4 insertions(+)

--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -87,6 +87,7 @@ struct cache_detail {
 					      int has_died);
 
 	struct cache_head *	(*alloc)(void);
+	void			(*flush)(void);
 	int			(*match)(struct cache_head *orig, struct cache_head *new);
 	void			(*init)(struct cache_head *orig, struct cache_head *new);
 	void			(*update)(struct cache_head *orig, struct cache_head *new);
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -1524,6 +1524,9 @@ static ssize_t write_flush(struct file *
 	cd->nextcheck = now;
 	cache_flush();
 
+	if (cd->flush)
+		cd->flush();
+
 	*ppos += count;
 	return count;
 }