fs: remove fget_many and fput_many interface

These two interface were added in 091141a commit,
but now there is no place to call them.

The only user of fput/fget_many() was removed in commit
62906e8 ("io_uring: remove file batch-get optimisation").

A user of get_file_rcu_many() were removed in commit
f073531 ("init: add an init_dup helper").

And replace atomic_long_sub/add to atomic_long_dec/inc
can improve performance.

Here are the test results of unixbench:

Cmd: ./Run -c 64 context1

Without patch:
System Benchmarks Partial Index              BASELINE       RESULT    INDEX
Pipe-based Context Switching                   4000.0    2798407.0   6996.0
                                                                   ========
System Benchmarks Index Score (Partial Only)                         6996.0

With patch:
System Benchmarks Partial Index              BASELINE       RESULT    INDEX
Pipe-based Context Switching                   4000.0    3486268.8   8715.7
                                                                   ========
System Benchmarks Index Score (Partial Only)                         8715.7

Signed-off-by: Gou Hao <gouhao@uniontech.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Author: Gou Hao

fs/file.c

@@ -871,7 +871,7 @@ void do_close_on_exec(struct files_struct *files)
 }
 
 static inline struct file *__fget_files_rcu(struct files_struct *files,
-	unsigned int fd, fmode_t mask, unsigned int refs)
+	unsigned int fd, fmode_t mask)
 {
 	for (;;) {
 		struct file *file;
@@ -897,10 +897,9 @@ static inline struct file *__fget_files_rcu(struct files_struct *files,
 		 * Such a race can take two forms:
 		 *
 		 *  (a) the file ref already went down to zero,
-		 *      and get_file_rcu_many() fails. Just try
-		 *      again:
+		 *      and get_file_rcu() fails. Just try again:
 		 */
-		if (unlikely(!get_file_rcu_many(file, refs)))
+		if (unlikely(!get_file_rcu(file)))
 			continue;
 
 		/*
@@ -909,11 +908,11 @@ static inline struct file *__fget_files_rcu(struct files_struct *files,
 		 *       pointer having changed, because it always goes
 		 *       hand-in-hand with 'fdt'.
 		 *
-		 * If so, we need to put our refs and try again.
+		 * If so, we need to put our ref and try again.
 		 */
 		if (unlikely(rcu_dereference_raw(files->fdt) != fdt) ||
 		    unlikely(rcu_dereference_raw(*fdentry) != file)) {
-			fput_many(file, refs);
+			fput(file);
 			continue;
 		}
 
@@ -926,37 +925,31 @@ static inline struct file *__fget_files_rcu(struct files_struct *files,
 }
 
 static struct file *__fget_files(struct files_struct *files, unsigned int fd,
-				 fmode_t mask, unsigned int refs)
+				 fmode_t mask)
 {
 	struct file *file;
 
 	rcu_read_lock();
-	file = __fget_files_rcu(files, fd, mask, refs);
+	file = __fget_files_rcu(files, fd, mask);
 	rcu_read_unlock();
 
 	return file;
 }
 
-static inline struct file *__fget(unsigned int fd, fmode_t mask,
-				  unsigned int refs)
-{
-	return __fget_files(current->files, fd, mask, refs);
-}
-
-struct file *fget_many(unsigned int fd, unsigned int refs)
+static inline struct file *__fget(unsigned int fd, fmode_t mask)
 {
-	return __fget(fd, FMODE_PATH, refs);
+	return __fget_files(current->files, fd, mask);
 }
 
 struct file *fget(unsigned int fd)
 {
-	return __fget(fd, FMODE_PATH, 1);
+	return __fget(fd, FMODE_PATH);
 }
 EXPORT_SYMBOL(fget);
 
 struct file *fget_raw(unsigned int fd)
 {
-	return __fget(fd, 0, 1);
+	return __fget(fd, 0);
 }
 EXPORT_SYMBOL(fget_raw);
 
@@ -966,7 +959,7 @@ struct file *fget_task(struct task_struct *task, unsigned int fd)
 
 	task_lock(task);
 	if (task->files)
-		file = __fget_files(task->files, fd, 0, 1);
+		file = __fget_files(task->files, fd, 0);
 	task_unlock(task);
 
 	return file;
@@ -1035,7 +1028,7 @@ static unsigned long __fget_light(unsigned int fd, fmode_t mask)
 			return 0;
 		return (unsigned long)file;
 	} else {
-		file = __fget(fd, mask, 1);
+		file = __fget(fd, mask);
 		if (!file)
 			return 0;
 		return FDPUT_FPUT | (unsigned long)file;

fs/file_table.c

@@ -368,9 +368,9 @@ EXPORT_SYMBOL_GPL(flush_delayed_fput);
 
 static DECLARE_DELAYED_WORK(delayed_fput_work, delayed_fput);
 
-void fput_many(struct file *file, unsigned int refs)
+void fput(struct file *file)
 {
-	if (atomic_long_sub_and_test(refs, &file->f_count)) {
+	if (atomic_long_dec_and_test(&file->f_count)) {
 		struct task_struct *task = current;
 
 		if (likely(!in_interrupt() && !(task->flags & PF_KTHREAD))) {
@@ -389,11 +389,6 @@ void fput_many(struct file *file, unsigned int refs)
 	}
 }
 
-void fput(struct file *file)
-{
-	fput_many(file, 1);
-}
-
 /*
  * synchronous analog of fput(); for kernel threads that might be needed
  * in some umount() (and thus can't use flush_delayed_fput() without

include/linux/file.h

@@ -14,7 +14,6 @@
 struct file;
 
 extern void fput(struct file *);
-extern void fput_many(struct file *, unsigned int);
 
 struct file_operations;
 struct task_struct;
@@ -47,7 +46,6 @@ static inline void fdput(struct fd fd)
 }
 
 extern struct file *fget(unsigned int fd);
-extern struct file *fget_many(unsigned int fd, unsigned int refs);
 extern struct file *fget_raw(unsigned int fd);
 extern struct file *fget_task(struct task_struct *task, unsigned int fd);
 extern unsigned long __fdget(unsigned int fd);

include/linux/fs.h

@@ -981,9 +981,7 @@ static inline struct file *get_file(struct file *f)
 	atomic_long_inc(&f->f_count);
 	return f;
 }
-#define get_file_rcu_many(x, cnt)	\
-	atomic_long_add_unless(&(x)->f_count, (cnt), 0)
-#define get_file_rcu(x) get_file_rcu_many((x), 1)
+#define get_file_rcu(x) atomic_long_inc_not_zero(&(x)->f_count)
 #define file_count(x)	atomic_long_read(&(x)->f_count)
 
 #define	MAX_NON_LFS	((1UL<<31) - 1)