locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

Please do not apply this to mainline directly, instead please re-run the
coccinelle script shown below and apply its output.

For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't harmful, and changing them results in
churn.

However, for some features, the read/write distinction is critical to
correct operation. To distinguish these cases, separate read/write
accessors must be used. This patch migrates (most) remaining
ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
coccinelle script:

----
// Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
// WRITE_ONCE()

// $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch

virtual patch

@ depends on patch @
expression E1, E2;
@@

- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)

@ depends on patch @
expression E;
@@

- ACCESS_ONCE(E)
+ READ_ONCE(E)
----

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

17 files changed, 27 insertions, 26 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 5a24872..e6de7715 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -576,7 +576,7 @@ static int kiocb_cancel(struct aio_kiocb *kiocb)
 	 * actually has a cancel function, hence the cmpxchg()
 	 */
 
-	cancel = ACCESS_ONCE(kiocb->ki_cancel);
+	cancel = READ_ONCE(kiocb->ki_cancel);
 	do {
 		if (!cancel || cancel == KIOCB_CANCELLED)
 			return -EINVAL;
diff --git a/fs/buffer.c b/fs/buffer.c
index 170df85..32ce01f 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1692,7 +1692,8 @@ static struct buffer_head *create_page_buffers(struct page *page, struct inode *
 	BUG_ON(!PageLocked(page));
 
 	if (!page_has_buffers(page))
-		create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
+		create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
+				     b_state);
 	return page_buffers(page);
 }
 
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index 8e704d1..0083bd4 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -373,7 +373,7 @@ void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
 	struct fscrypt_info *prev;
 
 	if (ci == NULL)
-		ci = ACCESS_ONCE(inode->i_crypt_info);
+		ci = READ_ONCE(inode->i_crypt_info);
 	if (ci == NULL)
 		return;
 
diff --git a/fs/direct-io.c b/fs/direct-io.c
index b53e66d..98fe132 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1152,7 +1152,7 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 		      get_block_t get_block, dio_iodone_t end_io,
 		      dio_submit_t submit_io, int flags)
 {
-	unsigned i_blkbits = ACCESS_ONCE(inode->i_blkbits);
+	unsigned i_blkbits = READ_ONCE(inode->i_blkbits);
 	unsigned blkbits = i_blkbits;
 	unsigned blocksize_mask = (1 << blkbits) - 1;
 	ssize_t retval = -EINVAL;
diff --git a/fs/exec.c b/fs/exec.c
index 3e14ba2..1d6243d 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1911,7 +1911,7 @@ void set_dumpable(struct mm_struct *mm, int value)
 		return;
 
 	do {
-		old = ACCESS_ONCE(mm->flags);
+		old = READ_ONCE(mm->flags);
 		new = (old & ~MMF_DUMPABLE_MASK) | value;
 	} while (cmpxchg(&mm->flags, old, new) != old);
 }
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 448a111..57bf296 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -724,7 +724,7 @@ static void send_sigio_to_task(struct task_struct *p,
 	 * F_SETSIG can change ->signum lockless in parallel, make
 	 * sure we read it once and use the same value throughout.
 	 */
-	int signum = ACCESS_ONCE(fown->signum);
+	int signum = READ_ONCE(fown->signum);
 
 	if (!sigio_perm(p, fown, signum))
 		return;
diff --git a/fs/fs_pin.c b/fs/fs_pin.c
index e747b3d..2d07f29 100644
--- a/fs/fs_pin.c
+++ b/fs/fs_pin.c
@@ -78,7 +78,7 @@ void mnt_pin_kill(struct mount *m)
 	while (1) {
 		struct hlist_node *p;
 		rcu_read_lock();
-		p = ACCESS_ONCE(m->mnt_pins.first);
+		p = READ_ONCE(m->mnt_pins.first);
 		if (!p) {
 			rcu_read_unlock();
 			break;
@@ -92,7 +92,7 @@ void group_pin_kill(struct hlist_head *p)
 	while (1) {
 		struct hlist_node *q;
 		rcu_read_lock();
-		q = ACCESS_ONCE(p->first);
+		q = READ_ONCE(p->first);
 		if (!q) {
 			rcu_read_unlock();
 			break;
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 13c65dd..a42d893 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -33,7 +33,7 @@ static struct fuse_dev *fuse_get_dev(struct file *file)
 	 * Lockless access is OK, because file->private data is set
 	 * once during mount and is valid until the file is released.
 	 */
-	return ACCESS_ONCE(file->private_data);
+	return READ_ONCE(file->private_data);
 }
 
 static void fuse_request_init(struct fuse_req *req, struct page **pages,
diff --git a/fs/inode.c b/fs/inode.c
index d1e35b5..fd40102 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2090,7 +2090,7 @@ void inode_set_flags(struct inode *inode, unsigned int flags,
 
 	WARN_ON_ONCE(flags & ~mask);
 	do {
-		old_flags = ACCESS_ONCE(inode->i_flags);
+		old_flags = READ_ONCE(inode->i_flags);
 		new_flags = (old_flags & ~mask) | flags;
 	} while (unlikely(cmpxchg(&inode->i_flags, old_flags,
 				  new_flags) != old_flags));
diff --git a/fs/namei.c b/fs/namei.c
index c75ea03..40a0f34 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1209,7 +1209,7 @@ static int follow_managed(struct path *path, struct nameidata *nd)
 	/* Given that we're not holding a lock here, we retain the value in a
 	 * local variable for each dentry as we look at it so that we don't see
 	 * the components of that value change under us */
-	while (managed = ACCESS_ONCE(path->dentry->d_flags),
+	while (managed = READ_ONCE(path->dentry->d_flags),
 	       managed &= DCACHE_MANAGED_DENTRY,
 	       unlikely(managed != 0)) {
 		/* Allow the filesystem to manage the transit without i_mutex
@@ -1394,7 +1394,7 @@ int follow_down(struct path *path)
 	unsigned managed;
 	int ret;
 
-	while (managed = ACCESS_ONCE(path->dentry->d_flags),
+	while (managed = READ_ONCE(path->dentry->d_flags),
 	       unlikely(managed & DCACHE_MANAGED_DENTRY)) {
 		/* Allow the filesystem to manage the transit without i_mutex
 		 * being held.
diff --git a/fs/namespace.c b/fs/namespace.c
index d18deb4..e158ec6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -353,7 +353,7 @@ int __mnt_want_write(struct vfsmount *m)
 	 * incremented count after it has set MNT_WRITE_HOLD.
 	 */
 	smp_mb();
-	while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
+	while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
 		cpu_relax();
 	/*
 	 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 5ceaeb1..f439f1c 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1081,7 +1081,7 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 	int error;
 
 	if (flags & LOOKUP_RCU) {
-		parent = ACCESS_ONCE(dentry->d_parent);
+		parent = READ_ONCE(dentry->d_parent);
 		dir = d_inode_rcu(parent);
 		if (!dir)
 			return -ECHILD;
@@ -1168,7 +1168,7 @@ out_set_verifier:
 	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
  out_valid:
 	if (flags & LOOKUP_RCU) {
-		if (parent != ACCESS_ONCE(dentry->d_parent))
+		if (parent != READ_ONCE(dentry->d_parent))
 			return -ECHILD;
 	} else
 		dput(parent);
@@ -1582,7 +1582,7 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 		struct inode *dir;
 
 		if (flags & LOOKUP_RCU) {
-			parent = ACCESS_ONCE(dentry->d_parent);
+			parent = READ_ONCE(dentry->d_parent);
 			dir = d_inode_rcu(parent);
 			if (!dir)
 				return -ECHILD;
@@ -1596,7 +1596,7 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 			ret = -ECHILD;
 		if (!(flags & LOOKUP_RCU))
 			dput(parent);
-		else if (parent != ACCESS_ONCE(dentry->d_parent))
+		else if (parent != READ_ONCE(dentry->d_parent))
 			return -ECHILD;
 		goto out;
 	}
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 77a8eac..375e8bf 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -453,7 +453,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 		cutime = sig->cutime;
 		cstime = sig->cstime;
 		cgtime = sig->cgtime;
-		rsslim = ACCESS_ONCE(sig->rlim[RLIMIT_RSS].rlim_cur);
+		rsslim = READ_ONCE(sig->rlim[RLIMIT_RSS].rlim_cur);
 
 		/* add up live thread stats at the group level */
 		if (whole) {
diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 99dff22..03afd51 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -27,7 +27,7 @@ static unsigned mounts_poll(struct file *file, poll_table *wait)
 
 	poll_wait(file, &p->ns->poll, wait);
 
-	event = ACCESS_ONCE(ns->event);
+	event = READ_ONCE(ns->event);
 	if (m->poll_event != event) {
 		m->poll_event = event;
 		res |= POLLERR | POLLPRI;
diff --git a/fs/splice.c b/fs/splice.c
index f3084cc..39e2dc0 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -253,7 +253,7 @@ EXPORT_SYMBOL(add_to_pipe);
  */
 int splice_grow_spd(const struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 {
-	unsigned int buffers = ACCESS_ONCE(pipe->buffers);
+	unsigned int buffers = READ_ONCE(pipe->buffers);
 
 	spd->nr_pages_max = buffers;
 	if (buffers <= PIPE_DEF_BUFFERS)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 1c713fd..f46d133 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -381,7 +381,7 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
 	 * in __get_user_pages if userfaultfd_release waits on the
 	 * caller of handle_userfault to release the mmap_sem.
 	 */
-	if (unlikely(ACCESS_ONCE(ctx->released))) {
+	if (unlikely(READ_ONCE(ctx->released))) {
 		/*
 		 * Don't return VM_FAULT_SIGBUS in this case, so a non
 		 * cooperative manager can close the uffd after the
@@ -477,7 +477,7 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
 						       vmf->flags, reason);
 	up_read(&mm->mmap_sem);
 
-	if (likely(must_wait && !ACCESS_ONCE(ctx->released) &&
+	if (likely(must_wait && !READ_ONCE(ctx->released) &&
 		   (return_to_userland ? !signal_pending(current) :
 		    !fatal_signal_pending(current)))) {
 		wake_up_poll(&ctx->fd_wqh, POLLIN);
@@ -586,7 +586,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
 		set_current_state(TASK_KILLABLE);
 		if (ewq->msg.event == 0)
 			break;
-		if (ACCESS_ONCE(ctx->released) ||
+		if (READ_ONCE(ctx->released) ||
 		    fatal_signal_pending(current)) {
 			/*
 			 * &ewq->wq may be queued in fork_event, but
@@ -833,7 +833,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
 	struct userfaultfd_wake_range range = { .len = 0, };
 	unsigned long new_flags;
 
-	ACCESS_ONCE(ctx->released) = true;
+	WRITE_ONCE(ctx->released, true);
 
 	if (!mmget_not_zero(mm))
 		goto wakeup;
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 51bf7b8..1299759 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -592,9 +592,9 @@ xlog_valid_lsn(
 	 * a transiently forward state. Instead, we can see the LSN in a
 	 * transiently behind state if we happen to race with a cycle wrap.
 	 */
-	cur_cycle = ACCESS_ONCE(log->l_curr_cycle);
+	cur_cycle = READ_ONCE(log->l_curr_cycle);
 	smp_rmb();
-	cur_block = ACCESS_ONCE(log->l_curr_block);
+	cur_block = READ_ONCE(log->l_curr_block);
 
 	if ((CYCLE_LSN(lsn) > cur_cycle) ||
 	    (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) {