From: Li Zhijian <lizhijian@cn.fujitsu.com>
To: <linux-mm@kvack.org>, <linux-rdma@vger.kernel.org>,
<akpm@linux-foundation.org>, <jglisse@redhat.com>, <jgg@ziepe.ca>,
<hch@infradead.org>
Cc: <yishaih@nvidia.com>, <linux-kernel@vger.kernel.org>,
Li Zhijian <lizhijian@cn.fujitsu.com>, <stable@vger.kernel.org>
Subject: [PATCH v3] mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled
Date: Mon, 30 Aug 2021 17:42:32 +0800 [thread overview]
Message-ID: <20210830094232.203029-1-lizhijian@cn.fujitsu.com> (raw)
Previously, we noticed the one rpma example was failed[1] since 36f30e486d,
where it will use ODP feature to do RDMA WRITE between fsdax files.
After digging into the code, we found hmm_vma_handle_pte() will still
return EFAULT even though all the its requesting flags has been
fulfilled. That's because a DAX page will be marked as
(_PAGE_SPECIAL | PAGE_DEVMAP) by pte_mkdevmap().
[1]: https://github.com/pmem/rpma/issues/1142
CC: stable@vger.kernel.org
Fixes: 405506274922 ("mm/hmm: add missing call to hmm_pte_need_fault in HMM_PFN_SPECIAL handling")
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
---
V3: adjust the checking order
---
mm/hmm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/mm/hmm.c b/mm/hmm.c
index fad6be2bf072..842e26599238 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -295,10 +295,13 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
goto fault;
/*
+ * Bypass devmap pte such as DAX page when all pfn requested
+ * flags(pfn_req_flags) are fulfilled.
* Since each architecture defines a struct page for the zero page, just
* fall through and treat it like a normal page.
*/
- if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
+ if (pte_special(pte) && !pte_devmap(pte) &&
+ !is_zero_pfn(pte_pfn(pte))) {
if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
pte_unmap(ptep);
return -EFAULT;
--
2.31.1
next reply other threads:[~2021-08-30 9:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-30 9:42 Li Zhijian [this message]
2021-08-30 10:09 ` [PATCH v3] mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled Christoph Hellwig
2021-08-30 12:40 ` Jason Gunthorpe
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