[PATCH] unpaged: VM_UNPAGED

Although we tend to associate VM_RESERVED with remap_pfn_range, quite a few
drivers set VM_RESERVED on areas which are then populated by nopage.  The
PageReserved removal in 2.6.15-rc1 changed VM_RESERVED not to free pages in
zap_pte_range, without changing those drivers not to set it: so their pages
just leak away.

Let's not change miscellaneous drivers now: introduce VM_UNPAGED at the core,
to flag the special areas where the ptes may have no struct page, or if they
have then it's not to be touched.  Replace most instances of VM_RESERVED in
core mm by VM_UNPAGED.  Force it on in remap_pfn_range, and the sparc and
sparc64 io_remap_pfn_range.

Revert addition of VM_RESERVED to powerpc vdso, it's not needed there.  Is it
needed anywhere?  It still governs the mm->reserved_vm statistic, and special
vmas not to be merged, and areas not to be core dumped; but could probably be
eliminated later (the drivers are probably specifying it because in 2.4 it
kept swapout off the vma, but in 2.6 we work from the LRU, which these pages
don't get on).

Use the VM_SHM slot for VM_UNPAGED, and define VM_SHM to 0: it serves no
purpose whatsoever, and should be removed from drivers when we clean up.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9701210c6680..f0cdfd18db55 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -144,7 +144,8 @@ extern unsigned int kobjsize(const void *objp);
 
 #define VM_GROWSDOWN    0x00000100      /* general info on the segment */
 #define VM_GROWSUP      0x00000200
-#define VM_SHM          0x00000400      /* shared memory area, don't swap out */
+#define VM_SHM          0x00000000      /* Means nothing: delete it later */
+#define VM_UNPAGED      0x00000400      /* Pages managed without map count */
 #define VM_DENYWRITE    0x00000800      /* ETXTBSY on write attempts.. */
 
 #define VM_EXECUTABLE   0x00001000
@@ -157,7 +158,7 @@ extern unsigned int kobjsize(const void *objp);
 
 #define VM_DONTCOPY     0x00020000      /* Do not copy this vma on fork */
 #define VM_DONTEXPAND   0x00040000      /* Cannot expand with mremap() */
-#define VM_RESERVED     0x00080000      /* Pages managed in a special way */
+#define VM_RESERVED     0x00080000      /* Count as reserved_vm like IO */
 #define VM_ACCOUNT      0x00100000      /* Is a VM accounted object */
 #define VM_HUGETLB      0x00400000      /* Huge TLB Page VM */
 #define VM_NONLINEAR    0x00800000      /* Is non-linear (remap_file_pages) */