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Don't bother with redoing rw_verify_area() from default_file_splice_from()

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default_file_splice_from() ends up calling vfs_write() (via very convoluted
callchain).  It's an overkill, since we already have done rw_verify_area()
in the caller by the time we call vfs_write() we are under set_fs(KERNEL_DS),
so access_ok() is also pointless.  Add a new helper (__kernel_write()),
use it instead of kernel_write() in there.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2013-03-20 13:19:30 -04:00
parent f6161aa153
commit 06ae43f34b
3 changed files with 33 additions and 1 deletions
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25
fs/read_write.c
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@ -17,6 +17,7 @@
#include <linux/splice.h>
#include <linux/compat.h>
#include "read_write.h"
#include "internal.h"
#include <asm/uaccess.h>
#include <asm/unistd.h>
@ -417,6 +418,30 @@ ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, lof
EXPORT_SYMBOL(do_sync_write);
ssize_t __kernel_write(struct file *file, const char *buf, size_t count, loff_t *pos)
{
mm_segment_t old_fs;
const char __user *p;
ssize_t ret;
old_fs = get_fs();
set_fs(get_ds());
p = (__force const char __user *)buf;
if (count > MAX_RW_COUNT)
count = MAX_RW_COUNT;
if (file->f_op->write)
ret = file->f_op->write(file, p, count, pos);
else
ret = do_sync_write(file, p, count, pos);
set_fs(old_fs);
if (ret > 0) {
fsnotify_modify(file);
add_wchar(current, ret);
}
inc_syscw(current);
return ret;
}
ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
ssize_t ret;