mm: introduce mm_populate() for populating new vmas

When creating new mappings using the MAP_POPULATE / MAP_LOCKED flags (or
with MCL_FUTURE in effect), we want to populate the pages within the
newly created vmas.  This may take a while as we may have to read pages
from disk, so ideally we want to do this outside of the write-locked
mmap_sem region.

This change introduces mm_populate(), which is used to defer populating
such mappings until after the mmap_sem write lock has been released.
This is implemented as a generalization of the former do_mlock_pages(),
which accomplished the same task but was using during mlock() /
mlockall().

Signed-off-by: Michel Lespinasse <walken@google.com>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Acked-by: Rik van Riel <riel@redhat.com>
Tested-by: Andy Lutomirski <luto@amacapital.net>
Cc: Greg Ungerer <gregungerer@westnet.com.au>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 3 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9d9dcc35d6a1..da0a0fe970c2 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1474,11 +1474,23 @@ extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned lo
 extern unsigned long mmap_region(struct file *file, unsigned long addr,
         unsigned long len, unsigned long flags,
         vm_flags_t vm_flags, unsigned long pgoff);
-extern unsigned long do_mmap_pgoff(struct file *, unsigned long,
-        unsigned long, unsigned long,
-        unsigned long, unsigned long);
+extern unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
+        unsigned long len, unsigned long prot, unsigned long flags,
+        unsigned long pgoff, bool *populate);
 extern int do_munmap(struct mm_struct *, unsigned long, size_t);
 
+#ifdef CONFIG_MMU
+extern int __mm_populate(unsigned long addr, unsigned long len,
+                         int ignore_errors);
+static inline void mm_populate(unsigned long addr, unsigned long len)
+{
+        /* Ignore errors */
+        (void) __mm_populate(addr, len, 1);
+}
+#else
+static inline void mm_populate(unsigned long addr, unsigned long len) {}
+#endif
+
 /* These take the mm semaphore themselves */
 extern unsigned long vm_brk(unsigned long, unsigned long);
 extern int vm_munmap(unsigned long, size_t);