[RFC PATCH 52/76] fscache: disable cookie when doing an invalidation for DIO write

[David Howells <dhowells@xxxxxxxxxx>]

From: Jeff Layton <jlayton@xxxxxxxxxx>

O_DIRECT I/O is probably a good indicator that we don't need to be
caching this file at the moment. Disable the cookie by treating it
as we would a NULL cookie after the invalidation completes. Reenable
when the last unuse is done.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 fs/fscache/cookie.c     |    9 ++++++++-
 include/linux/fscache.h |    9 ++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 1b30b28f7cf6..d20028535a86 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -427,8 +427,11 @@ void __fscache_unuse_cookie(struct fscache_cookie *cookie,
 {
 	if (aux_data || object_size)
 		__fscache_update_cookie(cookie, aux_data, object_size);
-	if (atomic_dec_and_test(&cookie->n_active))
+	if (atomic_dec_and_test(&cookie->n_active)) {
+		clear_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags);
+		smp_mb__after_atomic();
 		wake_up_var(&cookie->n_active);
+	}
 }
 EXPORT_SYMBOL(__fscache_unuse_cookie);
 
@@ -554,6 +557,10 @@ void __fscache_invalidate(struct fscache_cookie *cookie,
 	 */
 	ASSERTCMP(cookie->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
 
+	if ((flags & FSCACHE_INVAL_DIO_WRITE) &&
+	    test_and_set_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
+		return;
+
 	spin_lock(&cookie->lock);
 	fscache_update_aux(cookie, aux_data, &new_size);
 	cookie->zero_point = new_size;
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 1d141d17f63b..3c173fb660a6 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -26,11 +26,13 @@
 #define fscache_available() (1)
 #define fscache_cookie_valid(cookie) (cookie)
 #define fscache_object_valid(object) (object)
+#define fscache_cookie_enabled(cookie) (cookie && !test_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags))
 #else
 #define __fscache_available (0)
 #define fscache_available() (0)
 #define fscache_cookie_valid(cookie) (0)
 #define fscache_object_valid(object) (NULL)
+#define fscache_cookie_enabled(cookie) (0)
 #endif
 
 
@@ -127,6 +129,7 @@ struct fscache_cookie {
 
 	unsigned long			flags;
 #define FSCACHE_COOKIE_RELINQUISHED	6		/* T if cookie has been relinquished */
+#define FSCACHE_COOKIE_DISABLED		7		/* T if cookie has been disabled */
 
 	enum fscache_cookie_stage	stage;
 	enum fscache_cookie_type	type:8;
@@ -410,7 +413,7 @@ static inline
 void fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data,
 			   const loff_t *object_size)
 {
-	if (fscache_cookie_valid(cookie))
+	if (fscache_cookie_enabled(cookie))
 		__fscache_update_cookie(cookie, aux_data, object_size);
 }
 
@@ -468,7 +471,7 @@ static inline
 void fscache_invalidate(struct fscache_cookie *cookie,
 			const void *aux_data, loff_t size, unsigned int flags)
 {
-	if (fscache_cookie_valid(cookie))
+	if (fscache_cookie_enabled(cookie))
 		__fscache_invalidate(cookie, aux_data, size, flags);
 }
 
@@ -492,7 +495,7 @@ int fscache_begin_operation(struct fscache_cookie *cookie,
 			    struct fscache_op_resources *opr,
 			    enum fscache_want_stage want_stage)
 {
-	if (fscache_cookie_valid(cookie))
+	if (fscache_cookie_enabled(cookie))
 		return __fscache_begin_operation(cookie, opr, want_stage);
 	return -ENOBUFS;
 }