[PATCH] fs/lock: Don't allocate file_lock in flock_make_lock().

[Kuniyuki Iwashima <kuniyu@amazon.com>]

Two functions, flock syscall and locks_remove_flock(), call
flock_make_lock().  It allocates struct file_lock from slab
cache if its argument fl is NULL.

When we call flock syscall, we pass NULL to allocate memory
for struct file_lock.  However, we always free it at the end
by locks_free_lock().  We need not allocate it and instead
should use a local variable as locks_remove_flock() does.

Also, the validation for flock_translate_cmd() is not necessary
for locks_remove_flock().  So we move the part to flock syscall
and make flock_make_lock() return nothing.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 fs/locks.c | 57 +++++++++++++++++++-----------------------------------
 1 file changed, 20 insertions(+), 37 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index ca28e0e50e56..db75f4537abc 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -425,21 +425,9 @@ static inline int flock_translate_cmd(int cmd) {
 }
 
 /* Fill in a file_lock structure with an appropriate FLOCK lock. */
-static struct file_lock *
-flock_make_lock(struct file *filp, unsigned int cmd, struct file_lock *fl)
+static void flock_make_lock(struct file *filp, struct file_lock *fl, int type)
 {
-	int type = flock_translate_cmd(cmd);
-
-	if (type < 0)
-		return ERR_PTR(type);
-
-	if (fl == NULL) {
-		fl = locks_alloc_lock();
-		if (fl == NULL)
-			return ERR_PTR(-ENOMEM);
-	} else {
-		locks_init_lock(fl);
-	}
+	locks_init_lock(fl);
 
 	fl->fl_file = filp;
 	fl->fl_owner = filp;
@@ -447,8 +435,6 @@ flock_make_lock(struct file *filp, unsigned int cmd, struct file_lock *fl)
 	fl->fl_flags = FL_FLOCK;
 	fl->fl_type = type;
 	fl->fl_end = OFFSET_MAX;
-
-	return fl;
 }
 
 static int assign_type(struct file_lock *fl, long type)
@@ -2097,14 +2083,18 @@ EXPORT_SYMBOL(locks_lock_inode_wait);
  */
 SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
 {
-	struct fd f = fdget(fd);
-	struct file_lock *lock;
-	int can_sleep, unlock;
+	int can_sleep, unlock, type;
+	struct file_lock fl;
+	struct fd f;
 	int error;
 
-	error = -EBADF;
+	type = flock_translate_cmd(cmd);
+	if (type < 0)
+		return type;
+
+	f = fdget(fd);
 	if (!f.file)
-		goto out;
+		return -EBADF;
 
 	can_sleep = !(cmd & LOCK_NB);
 	cmd &= ~LOCK_NB;
@@ -2127,32 +2117,25 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
 		goto out_putf;
 	}
 
-	lock = flock_make_lock(f.file, cmd, NULL);
-	if (IS_ERR(lock)) {
-		error = PTR_ERR(lock);
-		goto out_putf;
-	}
+	flock_make_lock(f.file, &fl, type);
 
 	if (can_sleep)
-		lock->fl_flags |= FL_SLEEP;
+		fl.fl_flags |= FL_SLEEP;
 
-	error = security_file_lock(f.file, lock->fl_type);
+	error = security_file_lock(f.file, fl.fl_type);
 	if (error)
-		goto out_free;
+		goto out_putf;
 
 	if (f.file->f_op->flock)
 		error = f.file->f_op->flock(f.file,
-					  (can_sleep) ? F_SETLKW : F_SETLK,
-					  lock);
+					    can_sleep ? F_SETLKW : F_SETLK,
+					    &fl);
 	else
-		error = locks_lock_file_wait(f.file, lock);
-
- out_free:
-	locks_free_lock(lock);
+		error = locks_lock_file_wait(f.file, &fl);
 
  out_putf:
 	fdput(f);
- out:
+
 	return error;
 }
 
@@ -2614,7 +2597,7 @@ locks_remove_flock(struct file *filp, struct file_lock_context *flctx)
 	if (list_empty(&flctx->flc_flock))
 		return;
 
-	flock_make_lock(filp, LOCK_UN, &fl);
+	flock_make_lock(filp, &fl, flock_translate_cmd(LOCK_UN));
 	fl.fl_flags |= FL_CLOSE;
 
 	if (filp->f_op->flock)
-- 
2.30.2