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Subject[patch] fs: remove local variable copy of f_pos to enable thread-safe updates
From: Matti Linnanvuori <mattilinnanvuori@yahoo.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@yahoo.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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