[PATCH 06/45] fs: add do_lookup_dcookie() helper; remove in-kernel call to syscall

From: Dominik Brodowski
Date: Thu Mar 22 2018 - 05:14:16 EST


Using the fs-internal do_lookup_dcookie() helper allows us to get rid of
fs-internal calls to the sys_lookup_dcookie() syscall.

This patch is part of a series which tries to remove in-kernel calls to
syscalls. On this basis, the syscall entry path can be streamlined.

Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
fs/dcookies.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/dcookies.c b/fs/dcookies.c
index 0d0461cf2431..57bc96435feb 100644
--- a/fs/dcookies.c
+++ b/fs/dcookies.c
@@ -146,7 +146,7 @@ int get_dcookie(const struct path *path, unsigned long *cookie)
/* And here is where the userspace process can look up the cookie value
* to retrieve the path.
*/
-SYSCALL_DEFINE3(lookup_dcookie, u64, cookie64, char __user *, buf, size_t, len)
+static int do_lookup_dcookie(u64 cookie64, char __user *buf, size_t len)
{
unsigned long cookie = (unsigned long)cookie64;
int err = -EINVAL;
@@ -203,13 +203,18 @@ SYSCALL_DEFINE3(lookup_dcookie, u64, cookie64, char __user *, buf, size_t, len)
return err;
}

+SYSCALL_DEFINE3(lookup_dcookie, u64, cookie64, char __user *, buf, size_t, len)
+{
+ return do_lookup_dcookie(cookie64, buf, len);
+}
+
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(lookup_dcookie, u32, w0, u32, w1, char __user *, buf, compat_size_t, len)
{
#ifdef __BIG_ENDIAN
- return sys_lookup_dcookie(((u64)w0 << 32) | w1, buf, len);
+ return do_lookup_dcookie(((u64)w0 << 32) | w1, buf, len);
#else
- return sys_lookup_dcookie(((u64)w1 << 32) | w0, buf, len);
+ return do_lookup_dcookie(((u64)w1 << 32) | w0, buf, len);
#endif
}
#endif
--
2.16.2