Replace direct atomic operation for the file refcount witht the

refcount interface.
It also introduces the correct usage of memory barriers, as sometimes
fdrop() and fhold() are used with shared locks, which don't use any
release barrier.

2 files changed, 7 insertions, 5 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index cbb7653..201d7ca 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -1449,9 +1449,9 @@ falloc(struct thread *td, struct file **resultfp, int *resultfd)
 	 * descriptor to the list of open files at that point, otherwise
 	 * put it at the front of the list of open files.
 	 */
-	fp->f_count = 1;
+	refcount_init(&fp->f_count, 1);
 	if (resultfp)
-		fp->f_count++;
+		fhold(fp);
 	fp->f_cred = crhold(td->td_ucred);
 	fp->f_ops = &badfileops;
 	fp->f_data = NULL;
diff --git a/sys/sys/file.h b/sys/sys/file.h
index e3fdd60..3b05440 100644
--- a/sys/sys/file.h
+++ b/sys/sys/file.h
@@ -39,6 +39,7 @@
 #include <sys/unistd.h>
 #else
 #include <sys/queue.h>
+#include <sys/refcount.h>
 #include <sys/_lock.h>
 #include <sys/_mutex.h>
 
@@ -116,7 +117,7 @@ struct file {
 	short		f_type;		/* descriptor type */
 	short     	f_vnread_flags; /* (f) Sleep lock for f_offset */
 	volatile u_int	f_flag;		/* see fcntl.h */
-	volatile int 	f_count;	/* reference count */
+	volatile u_int 	f_count;	/* reference count */
 	/*
 	 *  DTYPE_VNODE specific fields.
 	 */
@@ -196,9 +197,10 @@ int fgetvp_write(struct thread *td, int fd, struct vnode **vpp);
 int fgetsock(struct thread *td, int fd, struct socket **spp, u_int *fflagp);
 void fputsock(struct socket *sp);
 
-#define	fhold(fp)	atomic_add_int(&(fp)->f_count, 1)
+#define	fhold(fp)							\
+	(refcount_acquire(&(fp)->f_count))
 #define	fdrop(fp, td)							\
-	(atomic_fetchadd_int(&(fp)->f_count, -1) <= 1 ? _fdrop((fp), (td)) : 0)
+	(refcount_release(&(fp)->f_count) ? _fdrop((fp), (td)) : 0)
 
 static __inline fo_rdwr_t	fo_read;
 static __inline fo_rdwr_t	fo_write;