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>
diff --git a/ipc/shm.c b/ipc/shm.c
index 4fa6d8f..9f047ba 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -967,11 +967,11 @@
unsigned long flags;
unsigned long prot;
int acc_mode;
- unsigned long user_addr;
struct ipc_namespace *ns;
struct shm_file_data *sfd;
struct path path;
fmode_t f_mode;
+ bool populate = false;
err = -EINVAL;
if (shmid < 0)
@@ -1070,13 +1070,15 @@
goto invalid;
}
- user_addr = do_mmap_pgoff(file, addr, size, prot, flags, 0);
- *raddr = user_addr;
+ addr = do_mmap_pgoff(file, addr, size, prot, flags, 0, &populate);
+ *raddr = addr;
err = 0;
- if (IS_ERR_VALUE(user_addr))
- err = (long)user_addr;
+ if (IS_ERR_VALUE(addr))
+ err = (long)addr;
invalid:
up_write(¤t->mm->mmap_sem);
+ if (populate)
+ mm_populate(addr, size);
out_fput:
fput(file);