linux-kernel - [PATCH 3/3] mm/hugetlb: page faults check for fallocate hole punch in progress and wait

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: <1445033310-13155-4-git-send-email-mike.kravetz@oracle.com>
Date:	Fri, 16 Oct 2015 15:08:30 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:	Dave Hansen <dave.hansen@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Kravetz <mike.kravetz@...cle.com>
Subject: [PATCH 3/3] mm/hugetlb: page faults check for fallocate hole punch in progress and wait

At page fault time, check i_private which indicates a fallocate hole punch
is in progress.  If the fault falls within the hole, wait for the hole
punch operation to complete before proceeding with the fault.

Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
 mm/hugetlb.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3c7db92..540d3a79 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3580,6 +3580,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	struct page *pagecache_page = NULL;
 	struct hstate *h = hstate_vma(vma);
 	struct address_space *mapping;
+	struct inode *inode = file_inode(vma->vm_file);
 	int need_wait_lock = 0;
 
 	address &= huge_page_mask(h);
@@ -3603,6 +3604,42 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	idx = vma_hugecache_offset(h, vma, address);
 
 	/*
+	 * page faults could race with fallocate hole punch.  If a page
+	 * is faulted between unmap and deallocation, it will still remain
+	 * in the punched hole.  During hole punch operations, a hugetlb_falloc
+	 * structure will be pointed to by i_private.  If this fault is for
+	 * a page in a hole being punched, wait for the operation to finish
+	 * before proceeding.
+	 *
+	 * Even with this strategy, it is still possible for a page fault to
+	 * race with hole punch.  However, the race window is considerably
+	 * smaller.
+	 */
+	if (unlikely(inode->i_private)) {
+		struct hugetlb_falloc *hugetlb_falloc;
+
+		spin_lock(&inode->i_lock);
+		hugetlb_falloc = inode->i_private;
+		if (hugetlb_falloc && hugetlb_falloc->waitq &&
+		    idx >= hugetlb_falloc->start &&
+		    idx <= hugetlb_falloc->end) {
+			wait_queue_head_t *hugetlb_falloc_waitq;
+			DEFINE_WAIT(hugetlb_fault_wait);
+
+			hugetlb_falloc_waitq = hugetlb_falloc->waitq;
+			prepare_to_wait(hugetlb_falloc_waitq,
+					&hugetlb_fault_wait,
+					TASK_UNINTERRUPTIBLE);
+			spin_unlock(&inode->i_lock);
+			schedule();
+
+			spin_lock(&inode->i_lock);
+			finish_wait(hugetlb_falloc_waitq, &hugetlb_fault_wait);
+		}
+		spin_unlock(&inode->i_lock);
+	}
+
+	/*
 	 * Serialize hugepage allocation and instantiation, so that we don't
 	 * get spurious allocation failures if two CPUs race to instantiate
 	 * the same page in the page cache.
-- 
2.4.3

--
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/