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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c 
 kernel/fs/btrfs/zstd.c
....@@ -6,25 +6,32 @@
66  */
77 
88 #include <linux/bio.h>
9
+#include <linux/bitmap.h>
910 #include <linux/err.h>
1011 #include <linux/init.h>
1112 #include <linux/kernel.h>
1213 #include <linux/mm.h>
14
+#include <linux/sched/mm.h>
1315 #include <linux/pagemap.h>
1416 #include <linux/refcount.h>
1517 #include <linux/sched.h>
1618 #include <linux/slab.h>
1719 #include <linux/zstd.h>
20
+#include "misc.h"
1821 #include "compression.h"
22
+#include "ctree.h"
1923 
2024 #define ZSTD_BTRFS_MAX_WINDOWLOG 17
2125 #define ZSTD_BTRFS_MAX_INPUT (1 << ZSTD_BTRFS_MAX_WINDOWLOG)
2226 #define ZSTD_BTRFS_DEFAULT_LEVEL 3
27
+#define ZSTD_BTRFS_MAX_LEVEL 15
28
+/* 307s to avoid pathologically clashing with transaction commit */
29
+#define ZSTD_BTRFS_RECLAIM_JIFFIES (307 * HZ)
2330 
24
-static ZSTD_parameters zstd_get_btrfs_parameters(size_t src_len)
31
+static ZSTD_parameters zstd_get_btrfs_parameters(unsigned int level,
32
+						 size_t src_len)
2533 {
26
-	ZSTD_parameters params = ZSTD_getParams(ZSTD_BTRFS_DEFAULT_LEVEL,
27
-						src_len, 0);
34
+	ZSTD_parameters params = ZSTD_getParams(level, src_len, 0);
2835 
2936 	if (params.cParams.windowLog > ZSTD_BTRFS_MAX_WINDOWLOG)
3037 		params.cParams.windowLog = ZSTD_BTRFS_MAX_WINDOWLOG;
....@@ -36,12 +43,295 @@
3643 	void *mem;
3744 	size_t size;
3845 	char *buf;
46
+	unsigned int level;
47
+	unsigned int req_level;
48
+	unsigned long last_used; /* jiffies */
3949 	struct list_head list;
50
+	struct list_head lru_list;
4051 	ZSTD_inBuffer in_buf;
4152 	ZSTD_outBuffer out_buf;
4253 };
4354 
44
-static void zstd_free_workspace(struct list_head *ws)
55
+/*
56
+ * Zstd Workspace Management
57
+ *
58
+ * Zstd workspaces have different memory requirements depending on the level.
59
+ * The zstd workspaces are managed by having individual lists for each level
60
+ * and a global lru.  Forward progress is maintained by protecting a max level
61
+ * workspace.
62
+ *
63
+ * Getting a workspace is done by using the bitmap to identify the levels that
64
+ * have available workspaces and scans up.  This lets us recycle higher level
65
+ * workspaces because of the monotonic memory guarantee.  A workspace's
66
+ * last_used is only updated if it is being used by the corresponding memory
67
+ * level.  Putting a workspace involves adding it back to the appropriate places
68
+ * and adding it back to the lru if necessary.
69
+ *
70
+ * A timer is used to reclaim workspaces if they have not been used for
71
+ * ZSTD_BTRFS_RECLAIM_JIFFIES.  This helps keep only active workspaces around.
72
+ * The upper bound is provided by the workqueue limit which is 2 (percpu limit).
73
+ */
74
+
75
+struct zstd_workspace_manager {
76
+	const struct btrfs_compress_op *ops;
77
+	spinlock_t lock;
78
+	struct list_head lru_list;
79
+	struct list_head idle_ws[ZSTD_BTRFS_MAX_LEVEL];
80
+	unsigned long active_map;
81
+	wait_queue_head_t wait;
82
+	struct timer_list timer;
83
+};
84
+
85
+static struct zstd_workspace_manager wsm;
86
+
87
+static size_t zstd_ws_mem_sizes[ZSTD_BTRFS_MAX_LEVEL];
88
+
89
+static inline struct workspace *list_to_workspace(struct list_head *list)
90
+{
91
+	return container_of(list, struct workspace, list);
92
+}
93
+
94
+void zstd_free_workspace(struct list_head *ws);
95
+struct list_head *zstd_alloc_workspace(unsigned int level);
96
+/*
97
+ * zstd_reclaim_timer_fn - reclaim timer
98
+ * @t: timer
99
+ *
100
+ * This scans the lru_list and attempts to reclaim any workspace that hasn't
101
+ * been used for ZSTD_BTRFS_RECLAIM_JIFFIES.
102
+ */
103
+static void zstd_reclaim_timer_fn(struct timer_list *timer)
104
+{
105
+	unsigned long reclaim_threshold = jiffies - ZSTD_BTRFS_RECLAIM_JIFFIES;
106
+	struct list_head *pos, *next;
107
+
108
+	spin_lock_bh(&wsm.lock);
109
+
110
+	if (list_empty(&wsm.lru_list)) {
111
+		spin_unlock_bh(&wsm.lock);
112
+		return;
113
+	}
114
+
115
+	list_for_each_prev_safe(pos, next, &wsm.lru_list) {
116
+		struct workspace *victim = container_of(pos, struct workspace,
117
+							lru_list);
118
+		unsigned int level;
119
+
120
+		if (time_after(victim->last_used, reclaim_threshold))
121
+			break;
122
+
123
+		/* workspace is in use */
124
+		if (victim->req_level)
125
+			continue;
126
+
127
+		level = victim->level;
128
+		list_del(&victim->lru_list);
129
+		list_del(&victim->list);
130
+		zstd_free_workspace(&victim->list);
131
+
132
+		if (list_empty(&wsm.idle_ws[level - 1]))
133
+			clear_bit(level - 1, &wsm.active_map);
134
+
135
+	}
136
+
137
+	if (!list_empty(&wsm.lru_list))
138
+		mod_timer(&wsm.timer, jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
139
+
140
+	spin_unlock_bh(&wsm.lock);
141
+}
142
+
143
+/*
144
+ * zstd_calc_ws_mem_sizes - calculate monotonic memory bounds
145
+ *
146
+ * It is possible based on the level configurations that a higher level
147
+ * workspace uses less memory than a lower level workspace.  In order to reuse
148
+ * workspaces, this must be made a monotonic relationship.  This precomputes
149
+ * the required memory for each level and enforces the monotonicity between
150
+ * level and memory required.
151
+ */
152
+static void zstd_calc_ws_mem_sizes(void)
153
+{
154
+	size_t max_size = 0;
155
+	unsigned int level;
156
+
157
+	for (level = 1; level <= ZSTD_BTRFS_MAX_LEVEL; level++) {
158
+		ZSTD_parameters params =
159
+			zstd_get_btrfs_parameters(level, ZSTD_BTRFS_MAX_INPUT);
160
+		size_t level_size =
161
+			max_t(size_t,
162
+			      ZSTD_CStreamWorkspaceBound(params.cParams),
163
+			      ZSTD_DStreamWorkspaceBound(ZSTD_BTRFS_MAX_INPUT));
164
+
165
+		max_size = max_t(size_t, max_size, level_size);
166
+		zstd_ws_mem_sizes[level - 1] = max_size;
167
+	}
168
+}
169
+
170
+void zstd_init_workspace_manager(void)
171
+{
172
+	struct list_head *ws;
173
+	int i;
174
+
175
+	zstd_calc_ws_mem_sizes();
176
+
177
+	wsm.ops = &btrfs_zstd_compress;
178
+	spin_lock_init(&wsm.lock);
179
+	init_waitqueue_head(&wsm.wait);
180
+	timer_setup(&wsm.timer, zstd_reclaim_timer_fn, 0);
181
+
182
+	INIT_LIST_HEAD(&wsm.lru_list);
183
+	for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++)
184
+		INIT_LIST_HEAD(&wsm.idle_ws[i]);
185
+
186
+	ws = zstd_alloc_workspace(ZSTD_BTRFS_MAX_LEVEL);
187
+	if (IS_ERR(ws)) {
188
+		pr_warn(
189
+		"BTRFS: cannot preallocate zstd compression workspace\n");
190
+	} else {
191
+		set_bit(ZSTD_BTRFS_MAX_LEVEL - 1, &wsm.active_map);
192
+		list_add(ws, &wsm.idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1]);
193
+	}
194
+}
195
+
196
+void zstd_cleanup_workspace_manager(void)
197
+{
198
+	struct workspace *workspace;
199
+	int i;
200
+
201
+	spin_lock_bh(&wsm.lock);
202
+	for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++) {
203
+		while (!list_empty(&wsm.idle_ws[i])) {
204
+			workspace = container_of(wsm.idle_ws[i].next,
205
+						 struct workspace, list);
206
+			list_del(&workspace->list);
207
+			list_del(&workspace->lru_list);
208
+			zstd_free_workspace(&workspace->list);
209
+		}
210
+	}
211
+	spin_unlock_bh(&wsm.lock);
212
+
213
+	del_timer_sync(&wsm.timer);
214
+}
215
+
216
+/*
217
+ * zstd_find_workspace - find workspace
218
+ * @level: compression level
219
+ *
220
+ * This iterates over the set bits in the active_map beginning at the requested
221
+ * compression level.  This lets us utilize already allocated workspaces before
222
+ * allocating a new one.  If the workspace is of a larger size, it is used, but
223
+ * the place in the lru_list and last_used times are not updated.  This is to
224
+ * offer the opportunity to reclaim the workspace in favor of allocating an
225
+ * appropriately sized one in the future.
226
+ */
227
+static struct list_head *zstd_find_workspace(unsigned int level)
228
+{
229
+	struct list_head *ws;
230
+	struct workspace *workspace;
231
+	int i = level - 1;
232
+
233
+	spin_lock_bh(&wsm.lock);
234
+	for_each_set_bit_from(i, &wsm.active_map, ZSTD_BTRFS_MAX_LEVEL) {
235
+		if (!list_empty(&wsm.idle_ws[i])) {
236
+			ws = wsm.idle_ws[i].next;
237
+			workspace = list_to_workspace(ws);
238
+			list_del_init(ws);
239
+			/* keep its place if it's a lower level using this */
240
+			workspace->req_level = level;
241
+			if (level == workspace->level)
242
+				list_del(&workspace->lru_list);
243
+			if (list_empty(&wsm.idle_ws[i]))
244
+				clear_bit(i, &wsm.active_map);
245
+			spin_unlock_bh(&wsm.lock);
246
+			return ws;
247
+		}
248
+	}
249
+	spin_unlock_bh(&wsm.lock);
250
+
251
+	return NULL;
252
+}
253
+
254
+/*
255
+ * zstd_get_workspace - zstd's get_workspace
256
+ * @level: compression level
257
+ *
258
+ * If @level is 0, then any compression level can be used.  Therefore, we begin
259
+ * scanning from 1.  We first scan through possible workspaces and then after
260
+ * attempt to allocate a new workspace.  If we fail to allocate one due to
261
+ * memory pressure, go to sleep waiting for the max level workspace to free up.
262
+ */
263
+struct list_head *zstd_get_workspace(unsigned int level)
264
+{
265
+	struct list_head *ws;
266
+	unsigned int nofs_flag;
267
+
268
+	/* level == 0 means we can use any workspace */
269
+	if (!level)
270
+		level = 1;
271
+
272
+again:
273
+	ws = zstd_find_workspace(level);
274
+	if (ws)
275
+		return ws;
276
+
277
+	nofs_flag = memalloc_nofs_save();
278
+	ws = zstd_alloc_workspace(level);
279
+	memalloc_nofs_restore(nofs_flag);
280
+
281
+	if (IS_ERR(ws)) {
282
+		DEFINE_WAIT(wait);
283
+
284
+		prepare_to_wait(&wsm.wait, &wait, TASK_UNINTERRUPTIBLE);
285
+		schedule();
286
+		finish_wait(&wsm.wait, &wait);
287
+
288
+		goto again;
289
+	}
290
+
291
+	return ws;
292
+}
293
+
294
+/*
295
+ * zstd_put_workspace - zstd put_workspace
296
+ * @ws: list_head for the workspace
297
+ *
298
+ * When putting back a workspace, we only need to update the LRU if we are of
299
+ * the requested compression level.  Here is where we continue to protect the
300
+ * max level workspace or update last_used accordingly.  If the reclaim timer
301
+ * isn't set, it is also set here.  Only the max level workspace tries and wakes
302
+ * up waiting workspaces.
303
+ */
304
+void zstd_put_workspace(struct list_head *ws)
305
+{
306
+	struct workspace *workspace = list_to_workspace(ws);
307
+
308
+	spin_lock_bh(&wsm.lock);
309
+
310
+	/* A node is only taken off the lru if we are the corresponding level */
311
+	if (workspace->req_level == workspace->level) {
312
+		/* Hide a max level workspace from reclaim */
313
+		if (list_empty(&wsm.idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1])) {
314
+			INIT_LIST_HEAD(&workspace->lru_list);
315
+		} else {
316
+			workspace->last_used = jiffies;
317
+			list_add(&workspace->lru_list, &wsm.lru_list);
318
+			if (!timer_pending(&wsm.timer))
319
+				mod_timer(&wsm.timer,
320
+					  jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
321
+		}
322
+	}
323
+
324
+	set_bit(workspace->level - 1, &wsm.active_map);
325
+	list_add(&workspace->list, &wsm.idle_ws[workspace->level - 1]);
326
+	workspace->req_level = 0;
327
+
328
+	spin_unlock_bh(&wsm.lock);
329
+
330
+	if (workspace->level == ZSTD_BTRFS_MAX_LEVEL)
331
+		cond_wake_up(&wsm.wait);
332
+}
333
+
334
+void zstd_free_workspace(struct list_head *ws)
45335 {
46336 	struct workspace *workspace = list_entry(ws, struct workspace, list);
47337 
....@@ -50,25 +340,25 @@
50340 	kfree(workspace);
51341 }
52342 
53
-static struct list_head *zstd_alloc_workspace(void)
343
+struct list_head *zstd_alloc_workspace(unsigned int level)
54344 {
55
-	ZSTD_parameters params =
56
-			zstd_get_btrfs_parameters(ZSTD_BTRFS_MAX_INPUT);
57345 	struct workspace *workspace;
58346 
59347 	workspace = kzalloc(sizeof(*workspace), GFP_KERNEL);
60348 	if (!workspace)
61349 		return ERR_PTR(-ENOMEM);
62350 
63
-	workspace->size = max_t(size_t,
64
-			ZSTD_CStreamWorkspaceBound(params.cParams),
65
-			ZSTD_DStreamWorkspaceBound(ZSTD_BTRFS_MAX_INPUT));
351
+	workspace->size = zstd_ws_mem_sizes[level - 1];
352
+	workspace->level = level;
353
+	workspace->req_level = level;
354
+	workspace->last_used = jiffies;
66355 	workspace->mem = kvmalloc(workspace->size, GFP_KERNEL);
67356 	workspace->buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
68357 	if (!workspace->mem || !workspace->buf)
69358 		goto fail;
70359 
71360 	INIT_LIST_HEAD(&workspace->list);
361
+	INIT_LIST_HEAD(&workspace->lru_list);
72362 
73363 	return &workspace->list;
74364 fail:
....@@ -76,13 +366,9 @@
76366 	return ERR_PTR(-ENOMEM);
77367 }
78368 
79
-static int zstd_compress_pages(struct list_head *ws,
80
-		struct address_space *mapping,
81
-		u64 start,
82
-		struct page **pages,
83
-		unsigned long *out_pages,
84
-		unsigned long *total_in,
85
-		unsigned long *total_out)
369
+int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
370
+		u64 start, struct page **pages, unsigned long *out_pages,
371
+		unsigned long *total_in, unsigned long *total_out)
86372 {
87373 	struct workspace *workspace = list_entry(ws, struct workspace, list);
88374 	ZSTD_CStream *stream;
....@@ -95,7 +381,8 @@
95381 	unsigned long len = *total_out;
96382 	const unsigned long nr_dest_pages = *out_pages;
97383 	unsigned long max_out = nr_dest_pages * PAGE_SIZE;
98
-	ZSTD_parameters params = zstd_get_btrfs_parameters(len);
384
+	ZSTD_parameters params = zstd_get_btrfs_parameters(workspace->req_level,
385
+							   len);
99386 
100387 	*out_pages = 0;
101388 	*total_out = 0;
....@@ -256,7 +543,7 @@
256543 	return ret;
257544 }
258545 
259
-static int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
546
+int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
260547 {
261548 	struct workspace *workspace = list_entry(ws, struct workspace, list);
262549 	struct page **pages_in = cb->compressed_pages;
....@@ -334,10 +621,9 @@
334621 	return ret;
335622 }
336623 
337
-static int zstd_decompress(struct list_head *ws, unsigned char *data_in,
338
-		struct page *dest_page,
339
-		unsigned long start_byte,
340
-		size_t srclen, size_t destlen)
624
+int zstd_decompress(struct list_head *ws, unsigned char *data_in,
625
+		struct page *dest_page, unsigned long start_byte, size_t srclen,
626
+		size_t destlen)
341627 {
342628 	struct workspace *workspace = list_entry(ws, struct workspace, list);
343629 	ZSTD_DStream *stream;
....@@ -419,15 +705,9 @@
419705 	return ret;
420706 }
421707 
422
-static void zstd_set_level(struct list_head *ws, unsigned int type)
423
-{
424
-}
425
-
426708 const struct btrfs_compress_op btrfs_zstd_compress = {
427
-	.alloc_workspace = zstd_alloc_workspace,
428
-	.free_workspace = zstd_free_workspace,
429
-	.compress_pages = zstd_compress_pages,
430
-	.decompress_bio = zstd_decompress_bio,
431
-	.decompress = zstd_decompress,
432
-	.set_level = zstd_set_level,
709
+	/* ZSTD uses own workspace manager */
710
+	.workspace_manager = NULL,
711
+	.max_level	= ZSTD_BTRFS_MAX_LEVEL,
712
+	.default_level	= ZSTD_BTRFS_DEFAULT_LEVEL,
433713 };