[PATCH 2/2] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for non-blocking

From: "Kuehling, Felix" <Felix.Kuehling-5C7GfCeVMHo@public.gmane.org>
To: "jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org"
	<jglisse-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
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	"airlied-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
	<airlied-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	"linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org"
	<linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
	"dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org"
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	<amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>
Cc: "Kuehling, Felix" <Felix.Kuehling-5C7GfCeVMHo@public.gmane.org>
Subject: [PATCH 2/2] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for non-blocking
Date: Fri, 10 May 2019 19:53:24 +0000	[thread overview]
Message-ID: <20190510195258.9930-3-Felix.Kuehling@amd.com> (raw)
In-Reply-To: <20190510195258.9930-1-Felix.Kuehling-5C7GfCeVMHo@public.gmane.org>

Don't set this flag by default in hmm_vma_do_fault. It is set
conditionally just a few lines below. Setting it unconditionally
can lead to handle_mm_fault doing a non-blocking fault, returning
-EBUSY and unlocking mmap_sem unexpectedly.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
---
 mm/hmm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index b65c27d5c119..3c4f1d62202f 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -339,7 +339,7 @@ struct hmm_vma_walk {
 static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
 			    bool write_fault, uint64_t *pfn)
 {
-	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
+	unsigned int flags = FAULT_FLAG_REMOTE;
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	struct vm_area_struct *vma = walk->vma;
-- 
2.17.1

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