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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, hch@lst.de, jgg@nvidia.com,
	linux-mm@kvack.org, lizhijian@cn.fujitsu.com,
	mm-commits@vger.kernel.org, stable@vger.kernel.org,
	torvalds@linux-foundation.org
Subject: [patch 1/8] mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled
Date: Wed, 08 Sep 2021 18:10:02 -0700	[thread overview]
Message-ID: <20210909011002.YtOxlcd0s%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210908180859.d523d4bb4ad8eec11c61500d@linux-foundation.org>

From: Li Zhijian <lizhijian@cn.fujitsu.com>
Subject: mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled

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

Link: https://lkml.kernel.org/r/20210830094232.203029-1-lizhijian@cn.fujitsu.com
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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hmm.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/hmm.c~mm-hmm-bypass-devmap-pte-when-all-pfn-requested-flags-are-fulfilled
+++ a/mm/hmm.c
@@ -295,10 +295,13 @@ static int hmm_vma_handle_pte(struct mm_
 		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;
_

  reply	other threads:[~2021-09-09  1:10 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-09  1:08 incoming Andrew Morton
2021-09-09  1:10 ` Andrew Morton [this message]
2021-09-09  1:10 ` [patch 2/8] mm/hugetlb: initialize hugetlb_usage in mm_init Andrew Morton
2021-09-09  1:10 ` [patch 3/8] mm,vmscan: fix divide by zero in get_scan_count Andrew Morton
2021-09-09  1:10 ` [patch 4/8] mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype Andrew Morton
2021-09-09  1:10 ` [patch 5/8] mmap_lock: change trace and locking order Andrew Morton
2021-09-09 12:56   ` Liam Howlett
2021-09-09  1:10 ` [patch 6/8] mm/kmemleak: allow __GFP_NOLOCKDEP passed to kmemleak's gfp Andrew Morton
2021-09-09  1:10 ` [patch 7/8] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task Andrew Morton
2021-09-09  1:10 ` [patch 8/8] nds32/setup: remove unused memblock_region variable in setup_memory() Andrew Morton

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