mm: new arch_remap() hook

Some architectures would like to be triggered when a memory area is moved
through the mremap system call.

This patch introduces a new arch_remap() mm hook which is placed in the
path of mremap, and is called before the old area is unmapped (and the
arch_unmap() hook is called).

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 20 insertions, 6 deletions

diff --git a/include/linux/mm-arch-hooks.h b/include/linux/mm-arch-hooks.h
index 63005e367abd..4efc3f56e6df 100644
--- a/include/linux/mm-arch-hooks.h
+++ b/include/linux/mm-arch-hooks.h
@@ -13,4 +13,13 @@
 
 #include <asm/mm-arch-hooks.h>
 
+#ifndef arch_remap
+static inline void arch_remap(struct mm_struct *mm,
+                              unsigned long old_start, unsigned long old_end,
+                              unsigned long new_start, unsigned long new_end)
+{
+}
+#define arch_remap arch_remap
+#endif
+
 #endif /* _LINUX_MM_ARCH_HOOKS_H */
diff --git a/mm/mremap.c b/mm/mremap.c
index 034e2d360652..a7c93eceb1c8 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -22,6 +22,7 @@
 #include <linux/mmu_notifier.h>
 #include <linux/sched/sysctl.h>
 #include <linux/uaccess.h>
+#include <linux/mm-arch-hooks.h>
 
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
@@ -286,13 +287,17 @@ static unsigned long move_vma(struct vm_area_struct *vma,
                 old_len = new_len;
                 old_addr = new_addr;
                 new_addr = -ENOMEM;
-        } else if (vma->vm_file && vma->vm_file->f_op->mremap) {
-                err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
-                if (err < 0) {
-                        move_page_tables(new_vma, new_addr, vma, old_addr,
-                                         moved_len, true);
-                        return err;
+        } else {
+                if (vma->vm_file && vma->vm_file->f_op->mremap) {
+                        err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
+                        if (err < 0) {
+                                move_page_tables(new_vma, new_addr, vma,
+                                                 old_addr, moved_len, true);
+                                return err;
+                        }
                 }
+                arch_remap(mm, old_addr, old_addr + old_len,
+                           new_addr, new_addr + new_len);
         }
 
         /* Conceal VM_ACCOUNT so old reservation is not undone */