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Date: Tue, 2 Jun 2015 09:59:12 -0700
From: Mike Kravetz <mike.kravetz@...cle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
Davidlohr Bueso <dave@...olabs.net>,
David Rientjes <rientjes@...gle.com>,
Luiz Capitulino <lcapitulino@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH v4 2/3] mm/hugetlb: compute/return the number of regions added by region_add()
Modify region_add() to keep track of regions(pages) added to the
reserve map and return this value. The return value can be
compared to the return value of region_chg() to determine if the
map was modified between calls.
Make vma_commit_reservation() also pass along the return value of
region_add(). In the normal case, we want vma_commit_reservation
to return the same value as the preceding call to vma_needs_reservation.
Create a common __vma_reservation_common routine to help keep the
special case return values in sync
Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
mm/hugetlb.c | 72 ++++++++++++++++++++++++++++++++++++++++--------------------
1 file changed, 48 insertions(+), 24 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4a1d702..cd3fc41 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -245,11 +245,15 @@ struct file_region {
* expanded, because region_add is only called after region_chg
* with the same range. If a new file_region structure must
* be allocated, it is done in region_chg.
+ *
+ * Return the number of new huge pages added to the map. This
+ * number is greater than or equal to zero.
*/
static long region_add(struct resv_map *resv, long f, long t)
{
struct list_head *head = &resv->regions;
struct file_region *rg, *nrg, *trg;
+ long add = 0;
spin_lock(&resv->lock);
/* Locate the region we are either in or before. */
@@ -275,14 +279,24 @@ static long region_add(struct resv_map *resv, long f, long t)
if (rg->to > t)
t = rg->to;
if (rg != nrg) {
+ /* Decrement return value by the deleted range.
+ * Another range will span this area so that by
+ * end of routine add will be >= zero
+ */
+ add -= (rg->to - rg->from);
list_del(&rg->link);
kfree(rg);
}
}
+
+ add += (nrg->from - f); /* Added to beginning of region */
nrg->from = f;
+ add += t - nrg->to; /* Added to end of region */
nrg->to = t;
+
spin_unlock(&resv->lock);
- return 0;
+ VM_BUG_ON(add < 0);
+ return add;
}
/*
@@ -1470,46 +1484,56 @@ static void return_unused_surplus_pages(struct hstate *h,
}
/*
- * Determine if the huge page at addr within the vma has an associated
- * reservation. Where it does not we will need to logically increase
- * reservation and actually increase subpool usage before an allocation
- * can occur. Where any new reservation would be required the
- * reservation change is prepared, but not committed. Once the page
- * has been allocated from the subpool and instantiated the change should
- * be committed via vma_commit_reservation. No action is required on
- * failure.
+ * vma_needs_reservation and vma_commit_reservation are used by the huge
+ * page allocation routines to manage reservations.
+ *
+ * vma_needs_reservation is called to determine if the huge page at addr
+ * within the vma has an associated reservation. If a reservation is
+ * needed, the value 1 is returned. The caller is then responsible for
+ * managing the global reservation and subpool usage counts. After
+ * the huge page has been allocated, vma_commit_reservation is called
+ * to add the page to the reservation map.
+ *
+ * In the normal case, vma_commit_reservation returns the same value
+ * as the preceding vma_needs_reservation call. The only time this
+ * is not the case is if a reserve map was changed between calls. It
+ * is the responsibility of the caller to notice the difference and
+ * take appropriate action.
*/
-static long vma_needs_reservation(struct hstate *h,
- struct vm_area_struct *vma, unsigned long addr)
+static long __vma_reservation_common(struct hstate *h,
+ struct vm_area_struct *vma, unsigned long addr,
+ bool commit)
{
struct resv_map *resv;
pgoff_t idx;
- long chg;
+ long ret;
resv = vma_resv_map(vma);
if (!resv)
return 1;
idx = vma_hugecache_offset(h, vma, addr);
- chg = region_chg(resv, idx, idx + 1);
+ if (commit)
+ ret = region_add(resv, idx, idx + 1);
+ else
+ ret = region_chg(resv, idx, idx + 1);
if (vma->vm_flags & VM_MAYSHARE)
- return chg;
+ return ret;
else
- return chg < 0 ? chg : 0;
+ return ret < 0 ? ret : 0;
}
-static void vma_commit_reservation(struct hstate *h,
+
+static long vma_needs_reservation(struct hstate *h,
struct vm_area_struct *vma, unsigned long addr)
{
- struct resv_map *resv;
- pgoff_t idx;
-
- resv = vma_resv_map(vma);
- if (!resv)
- return;
+ return __vma_reservation_common(h, vma, addr, false);
+}
- idx = vma_hugecache_offset(h, vma, addr);
- region_add(resv, idx, idx + 1);
+static long vma_commit_reservation(struct hstate *h,
+ struct vm_area_struct *vma, unsigned long addr)
+{
+ return __vma_reservation_common(h, vma, addr, true);
}
static struct page *alloc_huge_page(struct vm_area_struct *vma,
--
2.1.0
--
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