From bd2a31d522344b3ac2fb680bd2366e77a9bd8209 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 4 Mar 2014 14:54:22 -0500
Subject: [PATCH] get rid of fget_light()

instead of returning the flags by reference, we can just have the
low-level primitive return those in lower bits of unsigned long,
with struct file * derived from the rest.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/file.c            | 56 ++++++++++++++++++++++++++++++++++----------
 fs/read_write.c      | 16 +------------
 include/linux/file.h | 21 +++++++++--------
 include/linux/fs.h   |  2 +-
 4 files changed, 56 insertions(+), 39 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index db25c2bdfe46..60a45e9f5323 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -683,35 +683,65 @@ EXPORT_SYMBOL(fget_raw);
  * The fput_needed flag returned by fget_light should be passed to the
  * corresponding fput_light.
  */
-struct file *__fget_light(unsigned int fd, fmode_t mask, int *fput_needed)
+static unsigned long __fget_light(unsigned int fd, fmode_t mask)
 {
 	struct files_struct *files = current->files;
 	struct file *file;
 
-	*fput_needed = 0;
 	if (atomic_read(&files->count) == 1) {
 		file = __fcheck_files(files, fd);
-		if (file && (file->f_mode & mask))
-			file = NULL;
+		if (!file || unlikely(file->f_mode & mask))
+			return 0;
+		return (unsigned long)file;
 	} else {
 		file = __fget(fd, mask);
-		if (file)
-			*fput_needed = 1;
+		if (!file)
+			return 0;
+		return FDPUT_FPUT | (unsigned long)file;
 	}
-
-	return file;
 }
-struct file *fget_light(unsigned int fd, int *fput_needed)
+unsigned long __fdget(unsigned int fd)
 {
-	return __fget_light(fd, FMODE_PATH, fput_needed);
+	return __fget_light(fd, FMODE_PATH);
 }
-EXPORT_SYMBOL(fget_light);
+EXPORT_SYMBOL(__fdget);
 
-struct file *fget_raw_light(unsigned int fd, int *fput_needed)
+unsigned long __fdget_raw(unsigned int fd)
 {
-	return __fget_light(fd, 0, fput_needed);
+	return __fget_light(fd, 0);
 }
 
+unsigned long __fdget_pos(unsigned int fd)
+{
+	struct files_struct *files = current->files;
+	struct file *file;
+	unsigned long v;
+
+	if (atomic_read(&files->count) == 1) {
+		file = __fcheck_files(files, fd);
+		v = 0;
+	} else {
+		file = __fget(fd, 0);
+		v = FDPUT_FPUT;
+	}
+	if (!file)
+		return 0;
+
+	if (file->f_mode & FMODE_ATOMIC_POS) {
+		if (file_count(file) > 1) {
+			v |= FDPUT_POS_UNLOCK;
+			mutex_lock(&file->f_pos_lock);
+		}
+	}
+	return v | (unsigned long)file;
+}
+
+/*
+ * We only lock f_pos if we have threads or if the file might be
+ * shared with another process. In both cases we'll have an elevated
+ * file count (done either by fdget() or by fork()).
+ */
+
 void set_close_on_exec(unsigned int fd, int flag)
 {
 	struct files_struct *files = current->files;
diff --git a/fs/read_write.c b/fs/read_write.c
index 932bb3414a96..54e19b9392dc 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -264,23 +264,9 @@ loff_t vfs_llseek(struct file *file, loff_t offset, int whence)
 }
 EXPORT_SYMBOL(vfs_llseek);
 
-/*
- * We only lock f_pos if we have threads or if the file might be
- * shared with another process. In both cases we'll have an elevated
- * file count (done either by fdget() or by fork()).
- */
 static inline struct fd fdget_pos(int fd)
 {
-	struct fd f = fdget(fd);
-	struct file *file = f.file;
-
-	if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
-		if (file_count(file) > 1) {
-			f.flags |= FDPUT_POS_UNLOCK;
-			mutex_lock(&file->f_pos_lock);
-		}
-	}
-	return f;
+	return __to_fd(__fdget_pos(fd));
 }
 
 static inline void fdput_pos(struct fd f)
diff --git a/include/linux/file.h b/include/linux/file.h
index f2517fa2d610..4d69123377a2 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -40,23 +40,24 @@ static inline void fdput(struct fd fd)
 }
 
 extern struct file *fget(unsigned int fd);
-extern struct file *fget_light(unsigned int fd, int *fput_needed);
+extern struct file *fget_raw(unsigned int fd);
+extern unsigned long __fdget(unsigned int fd);
+extern unsigned long __fdget_raw(unsigned int fd);
+extern unsigned long __fdget_pos(unsigned int fd);
+
+static inline struct fd __to_fd(unsigned long v)
+{
+	return (struct fd){(struct file *)(v & ~3),v & 3};
+}
 
 static inline struct fd fdget(unsigned int fd)
 {
-	int b;
-	struct file *f = fget_light(fd, &b);
-	return (struct fd){f,b};
+	return __to_fd(__fdget(fd));
 }
 
-extern struct file *fget_raw(unsigned int fd);
-extern struct file *fget_raw_light(unsigned int fd, int *fput_needed);
-
 static inline struct fd fdget_raw(unsigned int fd)
 {
-	int b;
-	struct file *f = fget_raw_light(fd, &b);
-	return (struct fd){f,b};
+	return __to_fd(__fdget_raw(fd));
 }
 
 extern int f_dupfd(unsigned int from, struct file *file, unsigned flags);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ebfde04bca06..23b2a35d712e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -812,7 +812,7 @@ struct file {
 #ifdef CONFIG_DEBUG_WRITECOUNT
 	unsigned long f_mnt_write_state;
 #endif
-};
+} __attribute__((aligned(4)));	/* lest something weird decides that 2 is OK */
 
 struct file_handle {
 	__u32 handle_bytes;