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From: Alistair Popple <apopple@nvidia.com>
To: <akpm@linux-foundation.org>
Cc: rcampbell@nvidia.com, linux-doc@vger.kernel.org,
	nouveau@lists.freedesktop.org,
	Alistair Popple <apopple@nvidia.com>,
	hughd@google.com, linux-kernel@vger.kernel.org,
	willy@infradead.org, hch@infradead.org, linux-mm@kvack.org,
	peterx@redhat.com, shakeelb@google.com,
	dri-devel@lists.freedesktop.org, jgg@nvidia.com,
	bskeggs@redhat.com
Subject: [Nouveau] [PATCH v11 06/10] mm/memory.c: Allow different return codes for copy_nonpresent_pte()
Date: Wed, 16 Jun 2021 20:59:33 +1000	[thread overview]
Message-ID: <20210616105937.23201-7-apopple@nvidia.com> (raw)
In-Reply-To: <20210616105937.23201-1-apopple@nvidia.com>

Currently if copy_nonpresent_pte() returns a non-zero value it is
assumed to be a swap entry which requires further processing outside the
loop in copy_pte_range() after dropping locks. This prevents other
values being returned to signal conditions such as failure which a
subsequent change requires.

Instead make copy_nonpresent_pte() return an error code if further
processing is required and read the value for the swap entry in the main
loop under the ptl.

Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

---

v11:

Rebase on mmots

v10:

Use a unique error code and only check return codes for handling.

v9:

New for v9 to allow device exclusive handling to occur in
copy_nonpresent_pte().
---
 mm/memory.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index b4588402b777..1ac4d0b07c99 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -717,7 +717,7 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 
 	if (likely(!non_swap_entry(entry))) {
 		if (swap_duplicate(entry) < 0)
-			return entry.val;
+			return -EIO;
 
 		/* make sure dst_mm is on swapoff's mmlist. */
 		if (unlikely(list_empty(&dst_mm->mmlist))) {
@@ -973,12 +973,14 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
 			continue;
 		}
 		if (unlikely(!pte_present(*src_pte))) {
-			entry.val = copy_nonpresent_pte(dst_mm, src_mm,
-							dst_pte, src_pte,
-							dst_vma, src_vma,
-							addr, rss);
-			if (entry.val)
+			ret = copy_nonpresent_pte(dst_mm, src_mm,
+						  dst_pte, src_pte,
+						  dst_vma, src_vma,
+						  addr, rss);
+			if (ret == -EIO) {
+				entry = pte_to_swp_entry(*src_pte);
 				break;
+			}
 			progress += 8;
 			continue;
 		}
@@ -1011,20 +1013,24 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
 	pte_unmap_unlock(orig_dst_pte, dst_ptl);
 	cond_resched();
 
-	if (entry.val) {
+	if (ret == -EIO) {
+		VM_WARN_ON_ONCE(!entry.val);
 		if (add_swap_count_continuation(entry, GFP_KERNEL) < 0) {
 			ret = -ENOMEM;
 			goto out;
 		}
 		entry.val = 0;
-	} else if (ret) {
-		WARN_ON_ONCE(ret != -EAGAIN);
+	} else if (ret ==  -EAGAIN) {
 		prealloc = page_copy_prealloc(src_mm, src_vma, addr);
 		if (!prealloc)
 			return -ENOMEM;
-		/* We've captured and resolved the error. Reset, try again. */
-		ret = 0;
+	} else if (ret) {
+		VM_WARN_ON_ONCE(1);
 	}
+
+	/* We've captured and resolved the error. Reset, try again. */
+	ret = 0;
+
 	if (addr != end)
 		goto again;
 out:
-- 
2.20.1

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  parent reply	other threads:[~2021-06-16 11:01 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16 10:59 [Nouveau] [PATCH v11 00/10] Add support for SVM atomics in Nouveau Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 01/10] mm: Remove special swap entry functions Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 02/10] mm/swapops: Rework swap entry manipulation code Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 03/10] mm/rmap: Split try_to_munlock from try_to_unmap Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 04/10] mm/rmap: Split migration into its own function Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 05/10] mm: Rename migrate_pgmap_owner Alistair Popple
2021-06-16 10:59 ` Alistair Popple [this message]
2021-06-16 10:59 ` [Nouveau] [PATCH v11 07/10] mm: Device exclusive memory access Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 08/10] mm: Selftests for exclusive device memory Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 09/10] nouveau/svm: Refactor nouveau_range_fault Alistair Popple
2021-06-16 10:59 ` [Nouveau] [PATCH v11 10/10] nouveau/svm: Implement atomic SVM access Alistair Popple
2021-06-16 23:35 ` [Nouveau] [PATCH v11 00/10] Add support for SVM atomics in Nouveau Andrew Morton
2021-06-17  1:32   ` Alistair Popple
2021-06-17  1:29 ` [Nouveau] Update: " Alistair Popple

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