Stop playing silly games with the VM_ACCOUNT flag

The mmap_region() code would temporarily set the VM_ACCOUNT flag for
anonymous shared mappings just to inform shmem_zero_setup() that it
should enable accounting for the resulting shm object.  It would then
clear the flag after calling ->mmap (for the /dev/zero case) or doing
shmem_zero_setup() (for the MAP_ANON case).

This just resulted in vma merge issues, but also made for just
unnecessary confusion.  Use the already-existing VM_NORESERVE flag for
this instead, and let shmem_{zero|file}_setup() just figure it out from
that.

This also happens to make it obvious that the new DRI2 GEM layer uses a
non-reserving backing store for its object allocation - which is quite
possibly not intentional.  But since I didn't want to change semantics
in this patch, I left it alone, and just updated the caller to use the
new flag semantics.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/ipc/shm.c b/ipc/shm.c
index a9e09ad2263e..c0a021f7f41a 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -368,14 +368,14 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
                 file = hugetlb_file_setup(name, size);
                 shp->mlock_user = current_user();
         } else {
-                int acctflag = VM_ACCOUNT;
+                int acctflag = 0;
                 /*
                  * Do not allow no accounting for OVERCOMMIT_NEVER, even
                  * if it's asked for.
                  */
                 if  ((shmflg & SHM_NORESERVE) &&
                                 sysctl_overcommit_memory != OVERCOMMIT_NEVER)
-                        acctflag = 0;
+                        acctflag = VM_NORESERVE;
                 file = shmem_file_setup(name, size, acctflag);
         }
         error = PTR_ERR(file);