netdev - [PATCH v2 21/31] NFSD: Refactor __nfsd_file_close

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Date:   Tue, 28 Jun 2022 14:08:02 -0400
From:   Chuck Lever <chuck.lever@...cle.com>
To:     linux-nfs@...r.kernel.org, netdev@...r.kernel.org
Cc:     david@...morbit.com, jlayton@...hat.com, tgraf@...g.ch
Subject: [PATCH v2 21/31] NFSD: Refactor __nfsd_file_close_inode()

The code that computes the hashval is the same in both callers.

To prevent them from going stale, reframe the documenting comments
to remove descriptions of the underlying hash table structure, which
is about to be replaced.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
---
 fs/nfsd/filecache.c |   40 +++++++++++++++++++++-------------------
 fs/nfsd/trace.h     |   44 +++++++++++++++++++++++++++++++++-----------
 2 files changed, 54 insertions(+), 30 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 4143898fff37..9846ba543981 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -565,39 +565,44 @@ static struct shrinker	nfsd_file_shrinker = {
 	.seeks = 1,
 };
 
-static void
-__nfsd_file_close_inode(struct inode *inode, unsigned int hashval,
-			struct list_head *dispose)
+/*
+ * Find all cache items that match the inode and move them to @dispose.
+ * This process is atomic wrt nfsd_file_acquire().
+ */
+static unsigned int
+__nfsd_file_close_inode(struct inode *inode, struct list_head *dispose)
 {
+	unsigned int		hashval = (unsigned int)hash_long(inode->i_ino,
+						NFSD_FILE_HASH_BITS);
+	unsigned int		count = 0;
 	struct nfsd_file	*nf;
 	struct hlist_node	*tmp;
 
 	spin_lock(&nfsd_file_hashtbl[hashval].nfb_lock);
 	hlist_for_each_entry_safe(nf, tmp, &nfsd_file_hashtbl[hashval].nfb_head, nf_node) {
-		if (inode == nf->nf_inode)
+		if (inode == nf->nf_inode) {
 			nfsd_file_unhash_and_release_locked(nf, dispose);
+			count++;
+		}
 	}
 	spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock);
+	return count;
 }
 
 /**
  * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
- * Walk the whole hash bucket, looking for any files that correspond to "inode".
- * If any do, then unhash them and put the hashtable reference to them and
- * destroy any that had their last reference put. Also ensure that any of the
- * fputs also have their final __fput done as well.
+ * Unhash and put, then flush and fput all cache items associated with @inode.
  */
 void
 nfsd_file_close_inode_sync(struct inode *inode)
 {
-	unsigned int		hashval = (unsigned int)hash_long(inode->i_ino,
-						NFSD_FILE_HASH_BITS);
 	LIST_HEAD(dispose);
+	unsigned int count;
 
-	__nfsd_file_close_inode(inode, hashval, &dispose);
-	trace_nfsd_file_close_inode_sync(inode, !list_empty(&dispose));
+	count = __nfsd_file_close_inode(inode, &dispose);
+	trace_nfsd_file_close_inode_sync(inode, count);
 	nfsd_file_dispose_list_sync(&dispose);
 }
 
@@ -605,19 +610,16 @@ nfsd_file_close_inode_sync(struct inode *inode)
  * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
- * Walk the whole hash bucket, looking for any files that correspond to "inode".
- * If any do, then unhash them and put the hashtable reference to them and
- * destroy any that had their last reference put.
+ * Unhash and put all cache item associated with @inode.
  */
 static void
 nfsd_file_close_inode(struct inode *inode)
 {
-	unsigned int		hashval = (unsigned int)hash_long(inode->i_ino,
-						NFSD_FILE_HASH_BITS);
 	LIST_HEAD(dispose);
+	unsigned int count;
 
-	__nfsd_file_close_inode(inode, hashval, &dispose);
-	trace_nfsd_file_close_inode(inode, !list_empty(&dispose));
+	count = __nfsd_file_close_inode(inode, &dispose);
+	trace_nfsd_file_close_inode(inode, count);
 	nfsd_file_dispose_list_delayed(&dispose);
 }
 
diff --git a/fs/nfsd/trace.h b/fs/nfsd/trace.h
index 4b59c61ff41f..95aff644654a 100644
--- a/fs/nfsd/trace.h
+++ b/fs/nfsd/trace.h
@@ -804,30 +804,52 @@ TRACE_EVENT(nfsd_file_open,
 
 DECLARE_EVENT_CLASS(nfsd_file_search_class,
 	TP_PROTO(
-		struct inode *inode,
-		int found
+		const struct inode *inode,
+		unsigned int count
 	),
-	TP_ARGS(inode, found),
+	TP_ARGS(inode, count),
 	TP_STRUCT__entry(
-		__field(struct inode *, inode)
-		__field(int, found)
+		__field(const struct inode *, inode)
+		__field(unsigned int, count)
 	),
 	TP_fast_assign(
 		__entry->inode = inode;
-		__entry->found = found;
+		__entry->count = count;
 	),
-	TP_printk("inode=%p found=%d",
-		__entry->inode, __entry->found)
+	TP_printk("inode=%p count=%u",
+		__entry->inode, __entry->count)
 );
 
 #define DEFINE_NFSD_FILE_SEARCH_EVENT(name)				\
 DEFINE_EVENT(nfsd_file_search_class, name,				\
-	TP_PROTO(struct inode *inode, int found),			\
-	TP_ARGS(inode, found))
+	TP_PROTO(							\
+		const struct inode *inode,				\
+		unsigned int count					\
+	),								\
+	TP_ARGS(inode, count))
 
 DEFINE_NFSD_FILE_SEARCH_EVENT(nfsd_file_close_inode_sync);
 DEFINE_NFSD_FILE_SEARCH_EVENT(nfsd_file_close_inode);
-DEFINE_NFSD_FILE_SEARCH_EVENT(nfsd_file_is_cached);
+
+TRACE_EVENT(nfsd_file_is_cached,
+	TP_PROTO(
+		const struct inode *inode,
+		int found
+	),
+	TP_ARGS(inode, found),
+	TP_STRUCT__entry(
+		__field(const struct inode *, inode)
+		__field(int, found)
+	),
+	TP_fast_assign(
+		__entry->inode = inode;
+		__entry->found = found;
+	),
+	TP_printk("inode=%p is %scached",
+		__entry->inode,
+		__entry->found ? "" : "not "
+	)
+);
 
 TRACE_EVENT(nfsd_file_fsnotify_handle_event,
 	TP_PROTO(struct inode *inode, u32 mask),