mm/hugetlb: alloc_huge_page handle areas hole punched by fallocate

Areas hole punched by fallocate will not have entries in the
region/reserve map.  However, shared mappings with min_size subpool
reservations may still have reserved pages.  alloc_huge_page needs to
handle this special case and do the proper accounting.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index bd12e8c..114ad6c 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1733,34 +1733,58 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
        struct hugepage_subpool *spool = subpool_vma(vma);
        struct hstate *h = hstate_vma(vma);
        struct page *page;
-       long chg, commit;
+       long map_chg, map_commit;
+       long gbl_chg;
        int ret, idx;
        struct hugetlb_cgroup *h_cg;
 
        idx = hstate_index(h);
        /*
-        * Processes that did not create the mapping will have no
-        * reserves and will not have accounted against subpool
-        * limit. Check that the subpool limit can be made before
-        * satisfying the allocation MAP_NORESERVE mappings may also
-        * need pages and subpool limit allocated allocated if no reserve
-        * mapping overlaps.
+        * Examine the region/reserve map to determine if the process
+        * has a reservation for the page to be allocated.  A return
+        * code of zero indicates a reservation exists (no change).
         */
-       chg = vma_needs_reservation(h, vma, addr);
-       if (chg < 0)
+       map_chg = gbl_chg = vma_needs_reservation(h, vma, addr);
+       if (map_chg < 0)
                return ERR_PTR(-ENOMEM);
-       if (chg || avoid_reserve)
-               if (hugepage_subpool_get_pages(spool, 1) < 0) {
+
+       /*
+        * Processes that did not create the mapping will have no
+        * reserves as indicated by the region/reserve map. Check
+        * that the allocation will not exceed the subpool limit.
+        * Allocations for MAP_NORESERVE mappings also need to be
+        * checked against any subpool limit.
+        */
+       if (map_chg || avoid_reserve) {
+               gbl_chg = hugepage_subpool_get_pages(spool, 1);
+               if (gbl_chg < 0) {
                        vma_end_reservation(h, vma, addr);
                        return ERR_PTR(-ENOSPC);
                }
 
+               /*
+                * Even though there was no reservation in the region/reserve
+                * map, there could be reservations associated with the
+                * subpool that can be used.  This would be indicated if the
+                * return value of hugepage_subpool_get_pages() is zero.
+                * However, if avoid_reserve is specified we still avoid even
+                * the subpool reservations.
+                */
+               if (avoid_reserve)
+                       gbl_chg = 1;
+       }
+
        ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
        if (ret)
                goto out_subpool_put;
 
        spin_lock(&hugetlb_lock);
-       page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, chg);
+       /*
+        * glb_chg is passed to indicate whether or not a page must be taken
+        * from the global free pool (global change).  gbl_chg == 0 indicates
+        * a reservation exists for the allocation.
+        */
+       page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, gbl_chg);
        if (!page) {
                spin_unlock(&hugetlb_lock);
                page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
@@ -1776,8 +1800,8 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 
        set_page_private(page, (unsigned long)spool);
 
-       commit = vma_commit_reservation(h, vma, addr);
-       if (unlikely(chg > commit)) {
+       map_commit = vma_commit_reservation(h, vma, addr);
+       if (unlikely(map_chg > map_commit)) {
                /*
                 * The page was added to the reservation map between
                 * vma_needs_reservation and vma_commit_reservation.
@@ -1797,7 +1821,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 out_uncharge_cgroup:
        hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg);
 out_subpool_put:
-       if (chg || avoid_reserve)
+       if (map_chg || avoid_reserve)
                hugepage_subpool_put_pages(spool, 1);
        vma_end_reservation(h, vma, addr);
        return ERR_PTR(-ENOSPC);