shmem: fix shared anonymous accounting

[safe/jmp/linux-2.6] / mm / hugetlb.c

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2074642..107da3d 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2272,10 +2272,18 @@ int hugetlb_reserve_pages(struct inode *inode,
                                        struct vm_area_struct *vma,
                                        int acctflag)
 {
-       long ret = 0, chg;
+       long ret, chg;
        struct hstate *h = hstate_inode(inode);
 
        /*
+        * Only apply hugepage reservation if asked. At fault time, an
+        * attempt will be made for VM_NORESERVE to allocate a page
+        * and filesystem quota without using reserves
+        */
+       if (acctflag & VM_NORESERVE)
+               return 0;
+
+       /*
         * Shared mappings base their reservation on the number of pages that
         * are already allocated on behalf of the file. Private mappings need
         * to reserve the full area even if read-only as mprotect() may be
@@ -2283,42 +2291,47 @@ int hugetlb_reserve_pages(struct inode *inode,
         */
        if (!vma || vma->vm_flags & VM_SHARED)
                chg = region_chg(&inode->i_mapping->private_list, from, to);
-       else
+       else {
+               struct resv_map *resv_map = resv_map_alloc();
+               if (!resv_map)
+                       return -ENOMEM;
+
                chg = to - from;
 
+               set_vma_resv_map(vma, resv_map);
+               set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
+       }
+
        if (chg < 0)
                return chg;
 
+       /* There must be enough filesystem quota for the mapping */
        if (hugetlb_get_quota(inode->i_mapping, chg))
                return -ENOSPC;
 
        /*
-        * Only apply hugepage reservation if asked. We still have to
-        * take the filesystem quota because it is an upper limit
-        * defined for the mount and not necessarily memory as a whole
+        * Check enough hugepages are available for the reservation.
+        * Hand back the quota if there are not
         */
-       if (acctflag & VM_NORESERVE) {
-               reset_vma_resv_huge_pages(vma);
-               return 0;
-       }
-
        ret = hugetlb_acct_memory(h, chg);
        if (ret < 0) {
                hugetlb_put_quota(inode->i_mapping, chg);
                return ret;
        }
+
+       /*
+        * Account for the reservations made. Shared mappings record regions
+        * that have reservations as they are shared by multiple VMAs.
+        * When the last VMA disappears, the region map says how much
+        * the reservation was and the page cache tells how much of
+        * the reservation was consumed. Private mappings are per-VMA and
+        * only the consumed reservations are tracked. When the VMA
+        * disappears, the original reservation is the VMA size and the
+        * consumed reservations are stored in the map. Hence, nothing
+        * else has to be done for private mappings here
+        */
        if (!vma || vma->vm_flags & VM_SHARED)
                region_add(&inode->i_mapping->private_list, from, to);
-       else {
-               struct resv_map *resv_map = resv_map_alloc();
-
-               if (!resv_map)
-                       return -ENOMEM;
-
-               set_vma_resv_map(vma, resv_map);
-               set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
-       }
-
        return 0;
 }