From fc4ee73f68d0e9da4ba61112416849c18d933882 Mon Sep 17 00:00:00 2001

From: Sebastien Boeuf <sebastien.boeuf@intel.com>

Date: Mon, 23 Jan 2017 15:03:52 -0800

Subject: [PATCH 151/154] mm: Export do_madvise()

Combined with some interesting flags madvise() system call

allows to free memory more smartly and more efficiently than

we could do with a simple free(). The issue is that is not

available for kernel modules that could need it.

In order to solve this lack of support, this patch exports

do_madvise() so as to make it available to the entire kernel.

The already existing madvise() system call is unchanged and

now relies on this new do_madvise() function.

Suggested-by: Arjan van de Ven <arjan.van.de.ven@intel.com>

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

---

include/linux/mm.h | 2 ++

mm/madvise.c | 25 +++++++++++++++++++++----

2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h

index 43edf659453b..c3153e9ee7ea 100644

--- a/include/linux/mm.h

+++ b/include/linux/mm.h

@@ -2603,5 +2603,7 @@ void __init setup_nr_node_ids(void);

static inline void setup_nr_node_ids(void) {}

#endif

+extern int do_madvise(unsigned long start, size_t len_in, int behavior);

+

#endif /* __KERNEL__ */

#endif /* _LINUX_MM_H */

diff --git a/mm/madvise.c b/mm/madvise.c

index 375cf32087e4..3798dd68692e 100644

--- a/mm/madvise.c

+++ b/mm/madvise.c

@@ -730,9 +730,7 @@ madvise_behavior_valid(int behavior)

}

/*

- * The madvise(2) system call.

- *

- * Applications can use madvise() to advise the kernel how it should

+ * Kernel modules can use do_madvise() to advise the kernel how it should

* handle paging I/O in this VM area. The idea is to help the kernel

* use appropriate read-ahead and caching techniques. The information

* provided is advisory only, and can be safely disregarded by the

@@ -790,7 +788,7 @@ madvise_behavior_valid(int behavior)

* -EBADF - map exists, but area maps something that isn't a file.

* -EAGAIN - a kernel resource was temporarily unavailable.

*/

-SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)

+int do_madvise(unsigned long start, size_t len_in, int behavior)

{

unsigned long end, tmp;

struct vm_area_struct *vma, *prev;

@@ -885,3 +883,22 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)

return error;

}

+EXPORT_SYMBOL_GPL(do_madvise);

+

+/*

+ * The madvise(2) system call.

+ *

+ * Applications can use madvise() system call to advise the kernel how

+ * it should handle paging I/O in this VM area. The idea is to help

+ * the kernel use appropriate read-ahead and caching techniques. The

+ * information provided is advisory only, and can be safely disregarded

+ * by the kernel without affecting the correct operation of the application.

+ *

+ * behavior values are the same than the ones defined in madvise()

+ *

+ * return values are the same than the ones defined in madvise()

+ */

+SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)

+{

+ return do_madvise(start, len_in, behavior);

+}

--

2.15.0