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2024-05-10 10ebd8556b7990499c896a550e3d416b444211e6 
 kernel/mm/balloon_compaction.c
....@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  * mm/balloon_compaction.c
34  *
....@@ -10,101 +11,183 @@
1011 #include <linux/export.h>
1112 #include <linux/balloon_compaction.h>
1213 
14
+static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
15
+				     struct page *page)
16
+{
17
+	/*
18
+	 * Block others from accessing the 'page' when we get around to
19
+	 * establishing additional references. We should be the only one
20
+	 * holding a reference to the 'page' at this point. If we are not, then
21
+	 * memory corruption is possible and we should stop execution.
22
+	 */
23
+	BUG_ON(!trylock_page(page));
24
+	balloon_page_insert(b_dev_info, page);
25
+	unlock_page(page);
26
+	__count_vm_event(BALLOON_INFLATE);
27
+}
28
+
29
+/**
30
+ * balloon_page_list_enqueue() - inserts a list of pages into the balloon page
31
+ *				 list.
32
+ * @b_dev_info: balloon device descriptor where we will insert a new page to
33
+ * @pages: pages to enqueue - allocated using balloon_page_alloc.
34
+ *
35
+ * Driver must call this function to properly enqueue balloon pages before
36
+ * definitively removing them from the guest system.
37
+ *
38
+ * Return: number of pages that were enqueued.
39
+ */
40
+size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info,
41
+				 struct list_head *pages)
42
+{
43
+	struct page *page, *tmp;
44
+	unsigned long flags;
45
+	size_t n_pages = 0;
46
+
47
+	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
48
+	list_for_each_entry_safe(page, tmp, pages, lru) {
49
+		list_del(&page->lru);
50
+		balloon_page_enqueue_one(b_dev_info, page);
51
+		n_pages++;
52
+	}
53
+	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
54
+	return n_pages;
55
+}
56
+EXPORT_SYMBOL_GPL(balloon_page_list_enqueue);
57
+
58
+/**
59
+ * balloon_page_list_dequeue() - removes pages from balloon's page list and
60
+ *				 returns a list of the pages.
61
+ * @b_dev_info: balloon device decriptor where we will grab a page from.
62
+ * @pages: pointer to the list of pages that would be returned to the caller.
63
+ * @n_req_pages: number of requested pages.
64
+ *
65
+ * Driver must call this function to properly de-allocate a previous enlisted
66
+ * balloon pages before definitively releasing it back to the guest system.
67
+ * This function tries to remove @n_req_pages from the ballooned pages and
68
+ * return them to the caller in the @pages list.
69
+ *
70
+ * Note that this function may fail to dequeue some pages even if the balloon
71
+ * isn't empty - since the page list can be temporarily empty due to compaction
72
+ * of isolated pages.
73
+ *
74
+ * Return: number of pages that were added to the @pages list.
75
+ */
76
+size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
77
+				 struct list_head *pages, size_t n_req_pages)
78
+{
79
+	struct page *page, *tmp;
80
+	unsigned long flags;
81
+	size_t n_pages = 0;
82
+
83
+	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
84
+	list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
85
+		if (n_pages == n_req_pages)
86
+			break;
87
+
88
+		/*
89
+		 * Block others from accessing the 'page' while we get around to
90
+		 * establishing additional references and preparing the 'page'
91
+		 * to be released by the balloon driver.
92
+		 */
93
+		if (!trylock_page(page))
94
+			continue;
95
+
96
+		if (IS_ENABLED(CONFIG_BALLOON_COMPACTION) &&
97
+		    PageIsolated(page)) {
98
+			/* raced with isolation */
99
+			unlock_page(page);
100
+			continue;
101
+		}
102
+		balloon_page_delete(page);
103
+		__count_vm_event(BALLOON_DEFLATE);
104
+		list_add(&page->lru, pages);
105
+		unlock_page(page);
106
+		n_pages++;
107
+	}
108
+	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
109
+
110
+	return n_pages;
111
+}
112
+EXPORT_SYMBOL_GPL(balloon_page_list_dequeue);
113
+
13114 /*
14115  * balloon_page_alloc - allocates a new page for insertion into the balloon
15
- *			  page list.
116
+ *			page list.
16117  *
17
- * Driver must call it to properly allocate a new enlisted balloon page.
18
- * Driver must call balloon_page_enqueue before definitively removing it from
19
- * the guest system.  This function returns the page address for the recently
20
- * allocated page or NULL in the case we fail to allocate a new page this turn.
118
+ * Driver must call this function to properly allocate a new balloon page.
119
+ * Driver must call balloon_page_enqueue before definitively removing the page
120
+ * from the guest system.
121
+ *
122
+ * Return: struct page for the allocated page or NULL on allocation failure.
21123  */
22124 struct page *balloon_page_alloc(void)
23125 {
24126 	struct page *page = alloc_page(balloon_mapping_gfp_mask() |
25
-				       __GFP_NOMEMALLOC | __GFP_NORETRY);
127
+				       __GFP_NOMEMALLOC | __GFP_NORETRY |
128
+				       __GFP_NOWARN);
26129 	return page;
27130 }
28131 EXPORT_SYMBOL_GPL(balloon_page_alloc);
29132 
30133 /*
31
- * balloon_page_enqueue - allocates a new page and inserts it into the balloon
32
- *			  page list.
33
- * @b_dev_info: balloon device descriptor where we will insert a new page to
134
+ * balloon_page_enqueue - inserts a new page into the balloon page list.
135
+ *
136
+ * @b_dev_info: balloon device descriptor where we will insert a new page
34137  * @page: new page to enqueue - allocated using balloon_page_alloc.
35138  *
36
- * Driver must call it to properly enqueue a new allocated balloon page
37
- * before definitively removing it from the guest system.
38
- * This function returns the page address for the recently enqueued page or
39
- * NULL in the case we fail to allocate a new page this turn.
139
+ * Drivers must call this function to properly enqueue a new allocated balloon
140
+ * page before definitively removing the page from the guest system.
141
+ *
142
+ * Drivers must not call balloon_page_enqueue on pages that have been pushed to
143
+ * a list with balloon_page_push before removing them with balloon_page_pop. To
144
+ * enqueue a list of pages, use balloon_page_list_enqueue instead.
40145  */
41146 void balloon_page_enqueue(struct balloon_dev_info *b_dev_info,
42147 			  struct page *page)
43148 {
44149 	unsigned long flags;
45150 
46
-	/*
47
-	 * Block others from accessing the 'page' when we get around to
48
-	 * establishing additional references. We should be the only one
49
-	 * holding a reference to the 'page' at this point.
50
-	 */
51
-	BUG_ON(!trylock_page(page));
52151 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
53
-	balloon_page_insert(b_dev_info, page);
54
-	__count_vm_event(BALLOON_INFLATE);
152
+	balloon_page_enqueue_one(b_dev_info, page);
55153 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
56
-	unlock_page(page);
57154 }
58155 EXPORT_SYMBOL_GPL(balloon_page_enqueue);
59156 
60157 /*
61158  * balloon_page_dequeue - removes a page from balloon's page list and returns
62
- *			  the its address to allow the driver release the page.
159
+ *			  its address to allow the driver to release the page.
63160  * @b_dev_info: balloon device decriptor where we will grab a page from.
64161  *
65
- * Driver must call it to properly de-allocate a previous enlisted balloon page
66
- * before definetively releasing it back to the guest system.
67
- * This function returns the page address for the recently dequeued page or
68
- * NULL in the case we find balloon's page list temporarily empty due to
69
- * compaction isolated pages.
162
+ * Driver must call this function to properly dequeue a previously enqueued page
163
+ * before definitively releasing it back to the guest system.
164
+ *
165
+ * Caller must perform its own accounting to ensure that this
166
+ * function is called only if some pages are actually enqueued.
167
+ *
168
+ * Note that this function may fail to dequeue some pages even if there are
169
+ * some enqueued pages - since the page list can be temporarily empty due to
170
+ * the compaction of isolated pages.
171
+ *
172
+ * TODO: remove the caller accounting requirements, and allow caller to wait
173
+ * until all pages can be dequeued.
174
+ *
175
+ * Return: struct page for the dequeued page, or NULL if no page was dequeued.
70176  */
71177 struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info)
72178 {
73
-	struct page *page, *tmp;
74179 	unsigned long flags;
75
-	bool dequeued_page;
180
+	LIST_HEAD(pages);
181
+	int n_pages;
76182 
77
-	dequeued_page = false;
78
-	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
79
-	list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) {
80
-		/*
81
-		 * Block others from accessing the 'page' while we get around
82
-		 * establishing additional references and preparing the 'page'
83
-		 * to be released by the balloon driver.
84
-		 */
85
-		if (trylock_page(page)) {
86
-#ifdef CONFIG_BALLOON_COMPACTION
87
-			if (PageIsolated(page)) {
88
-				/* raced with isolation */
89
-				unlock_page(page);
90
-				continue;
91
-			}
92
-#endif
93
-			balloon_page_delete(page);
94
-			__count_vm_event(BALLOON_DEFLATE);
95
-			unlock_page(page);
96
-			dequeued_page = true;
97
-			break;
98
-		}
99
-	}
100
-	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
183
+	n_pages = balloon_page_list_dequeue(b_dev_info, &pages, 1);
101184 
102
-	if (!dequeued_page) {
185
+	if (n_pages != 1) {
103186 		/*
104187 		 * If we are unable to dequeue a balloon page because the page
105
-		 * list is empty and there is no isolated pages, then something
188
+		 * list is empty and there are no isolated pages, then something
106189 		 * went out of track and some balloon pages are lost.
107
-		 * BUG() here, otherwise the balloon driver may get stuck into
190
+		 * BUG() here, otherwise the balloon driver may get stuck in
108191 		 * an infinite loop while attempting to release all its pages.
109192 		 */
110193 		spin_lock_irqsave(&b_dev_info->pages_lock, flags);
....@@ -112,9 +195,9 @@
112195 			     !b_dev_info->isolated_pages))
113196 			BUG();
114197 		spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
115
-		page = NULL;
198
+		return NULL;
116199 	}
117
-	return page;
200
+	return list_first_entry(&pages, struct page, lru);
118201 }
119202 EXPORT_SYMBOL_GPL(balloon_page_dequeue);
120203 
....@@ -155,8 +238,8 @@
155238 
156239 	/*
157240 	 * We can not easily support the no copy case here so ignore it as it
158
-	 * is unlikely to be use with ballon pages. See include/linux/hmm.h for
159
-	 * user of the MIGRATE_SYNC_NO_COPY mode.
241
+	 * is unlikely to be used with balloon pages. See include/linux/hmm.h
242
+	 * for a user of the MIGRATE_SYNC_NO_COPY mode.
160243 	 */
161244 	if (mode == MIGRATE_SYNC_NO_COPY)
162245 		return -EINVAL;