From: Miaohe Lin <linmiaohe@huawei.com>
To: <akpm@linux-foundation.org>
Cc: <ying.huang@intel.com>, <dennis@kernel.org>,
<tim.c.chen@linux.intel.com>, <hughd@google.com>,
<hannes@cmpxchg.org>, <mhocko@suse.com>, <iamjoonsoo.kim@lge.com>,
<alexs@kernel.org>, <willy@infradead.org>, <minchan@kernel.org>,
<richard.weiyang@gmail.com>, <shy828301@gmail.com>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<linmiaohe@huawei.com>
Subject: [PATCH v3 4/4] mm/shmem: fix shmem_swapin() race with swapoff
Date: Tue, 20 Apr 2021 09:30:48 -0400 [thread overview]
Message-ID: <20210420133048.6773-5-linmiaohe@huawei.com> (raw)
In-Reply-To: <20210420133048.6773-1-linmiaohe@huawei.com>
When I was investigating the swap code, I found the below possible race
window:
CPU 1 CPU 2
----- -----
shmem_swapin
swap_cluster_readahead
if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) {
swapoff
percpu_ref_kill(&p->users)
synchronize_rcu()
wait_for_completion
..
si->swap_file = NULL;
struct inode *inode = si->swap_file->f_mapping->host;[oops!]
Close this race window by using get/put_swap_device() to guard against
concurrent swapoff.
Fixes: 8fd2e0b505d1 ("mm: swap: check if swap backing device is congested or not")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/shmem.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/shmem.c b/mm/shmem.c
index 26c76b13ad23..936ba5595297 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1492,15 +1492,21 @@ static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
+ struct swap_info_struct *si;
struct vm_area_struct pvma;
struct page *page;
struct vm_fault vmf = {
.vma = &pvma,
};
+ /* Prevent swapoff from happening to us. */
+ si = get_swap_device(swap);
+ if (unlikely(!si))
+ return NULL;
shmem_pseudo_vma_init(&pvma, info, index);
page = swap_cluster_readahead(swap, gfp, &vmf);
shmem_pseudo_vma_destroy(&pvma);
+ put_swap_device(si);
return page;
}
--
2.19.1
next prev parent reply other threads:[~2021-04-20 13:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 13:30 [PATCH v3 0/4] close various race windows for swap Miaohe Lin
2021-04-20 13:30 ` [PATCH v3 1/4] mm/swapfile: use percpu_ref to serialize against concurrent swapoff Miaohe Lin
2021-04-21 1:05 ` Huang, Ying
2021-04-21 1:59 ` Miaohe Lin
2021-04-20 13:30 ` [PATCH v3 2/4] swap: fix do_swap_page() race with swapoff Miaohe Lin
2021-04-21 0:52 ` Huang, Ying
2021-04-20 13:30 ` [PATCH v3 3/4] mm/swap: remove confusing checking for non_swap_entry() in swap_ra_info() Miaohe Lin
2021-04-21 0:58 ` Huang, Ying
2021-04-20 13:30 ` Miaohe Lin [this message]
2021-04-21 1:02 ` [PATCH v3 4/4] mm/shmem: fix shmem_swapin() race with swapoff Huang, Ying
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