linux-kernel - [patch] fs: remove local variable copy of f

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Date:	Fri, 2 May 2008 02:14:25 -0700 (PDT)
From:	Matti Linnanvuori <mattilinnanvuori@...oo.com>
To:	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: [patch] fs: remove local variable copy of f_pos to enable thread-safe updates

From: Matti Linnanvuori <mattilinnanvuori@...oo.com>

Remove local variable copy of f_pos to enable thread-safe updates in
implementation functions of system calls read, readv, write and writev.

Signed-off-by: Matti Linnanvuori <mattilinnanvuori@...oo.com>

---

--- linux-next/fs/fs-read_write.c    2008-05-02 11:54:04.715996700 +0300
+++ linux-2.6/fs/fs-read_write.c    2008-05-02 11:57:17.011641000 +0300
@@ -348,16 +348,6 @@ ssize_t vfs_write(struct file *file, con
 
 EXPORT_SYMBOL(vfs_write);
 
-static inline loff_t file_pos_read(struct file *file)
-{
-    return file->f_pos;
-}
-
-static inline void file_pos_write(struct file *file, loff_t pos)
-{
-    file->f_pos = pos;
-}
-
 asmlinkage ssize_t sys_read(unsigned int fd, char __user * buf, size_t count)
 {
     struct file *file;
@@ -366,10 +356,8 @@ asmlinkage ssize_t sys_read(unsigned int
 
     file = fget_light(fd, &fput_needed);
     if (file) {
-        loff_t pos = file_pos_read(file);
         trace_mark(fs_read, "fd %u count %zu", fd, count);
-        ret = vfs_read(file, buf, count, &pos);
-        file_pos_write(file, pos);
+        ret = vfs_read(file, buf, count, &file->f_pos);
         fput_light(file, fput_needed);
     }
 
@@ -384,10 +372,8 @@ asmlinkage ssize_t sys_write(unsigned in
 
     file = fget_light(fd, &fput_needed);
     if (file) {
-        loff_t pos = file_pos_read(file);
         trace_mark(fs_write, "fd %u count %zu", fd, count);
-        ret = vfs_write(file, buf, count, &pos);
-        file_pos_write(file, pos);
+        ret = vfs_write(file, buf, count, &file->f_pos);
         fput_light(file, fput_needed);
     }
 
@@ -679,10 +665,8 @@ sys_readv(unsigned long fd, const struct
 
     file = fget_light(fd, &fput_needed);
     if (file) {
-        loff_t pos = file_pos_read(file);
         trace_mark(fs_readv, "fd %lu vlen %lu", fd, vlen);
-        ret = vfs_readv(file, vec, vlen, &pos);
-        file_pos_write(file, pos);
+        ret = vfs_readv(file, vec, vlen, &file->f_pos);
         fput_light(file, fput_needed);
     }
 
@@ -701,10 +685,8 @@ sys_writev(unsigned long fd, const struc
 
     file = fget_light(fd, &fput_needed);
     if (file) {
-        loff_t pos = file_pos_read(file);
         trace_mark(fs_writev, "fd %lu vlen %lu", fd, vlen);
-        ret = vfs_writev(file, vec, vlen, &pos);
-        file_pos_write(file, pos);
+        ret = vfs_writev(file, vec, vlen, &file->f_pos);
         fput_light(file, fput_needed);
     }


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