linux-kernel - [PATCH v3 06/10] mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1436761268-6397-7-git-send-email-mike.kravetz@oracle.com>
Date:	Sun, 12 Jul 2015 21:21:04 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Cc:	Dave Hansen <dave.hansen@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH v3 06/10] mm/hugetlb: vma_has_reserves() needs to handle fallocate hole punch

In vma_has_reserves(), the current assumption is that reserves are
always present for shared mappings.  However, this will not be the
case with fallocate hole punch.  When punching a hole, the present
page will be deleted as well as the region/reserve map entry (and
hence any reservation).  vma_has_reserves is passed "chg" which
indicates whether or not a region/reserve map is present.  Use
this to determine if reserves are actually present or were removed
via hole punch.

Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
 mm/hugetlb.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index def39e3..f72cb96 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -801,9 +801,19 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
 			return 0;
 	}
 
-	/* Shared mappings always use reserves */
-	if (vma->vm_flags & VM_MAYSHARE)
-		return 1;
+	if (vma->vm_flags & VM_MAYSHARE) {
+		/*
+		 * We know VM_NORESERVE is not set.  Therefore, there SHOULD
+		 * be a region map for all pages.  The only situation where
+		 * there is no region map is if a hole was punched via
+		 * fallocate.  In this case, there really are no reverves to
+		 * use.  This situation is indicated if chg != 0.
+		 */
+		if (chg)
+			return 0;
+		else
+			return 1;
+	}
 
 	/*
 	 * Only the process that called mmap() has reserves for
-- 
2.1.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/