1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  Copyright (c) 2013
4  *  Minchan Kim <minchan@kernel.org>
5  */
6 #include <linux/types.h>
7 #include <linux/mutex.h>
8 #include <linux/slab.h>
9 #include <linux/bio.h>
10 #include <linux/sched.h>
11 #include <linux/wait.h>
12 #include <linux/cpumask.h>
13 
14 #include "squashfs_fs.h"
15 #include "squashfs_fs_sb.h"
16 #include "decompressor.h"
17 #include "squashfs.h"
18 
19 /*
20  * This file implements multi-threaded decompression in the
21  * decompressor framework
22  */
23 
24 
25 /*
26  * The reason that multiply two is that a CPU can request new I/O
27  * while it is waiting previous request.
28  */
29 #define MAX_DECOMPRESSOR	(num_online_cpus() * 2)
30 
31 
32 static int squashfs_max_decompressors(void)
33 {
34 	return MAX_DECOMPRESSOR;
35 }
36 
37 struct squashfs_stream {
38 	void			*comp_opts;
39 	struct list_head	strm_list;
40 	struct mutex		mutex;
41 	int			avail_decomp;
42 	wait_queue_head_t	wait;
43 };
44 
45 
46 struct decomp_stream {
47 	void *stream;
48 	struct list_head list;
49 };
50 
51 
52 static void put_decomp_stream(struct decomp_stream *decomp_strm,
53 				struct squashfs_stream *stream)
54 {
55 	mutex_lock(&stream->mutex);
56 	list_add(&decomp_strm->list, &stream->strm_list);
57 	mutex_unlock(&stream->mutex);
58 	wake_up(&stream->wait);
59 }
60 
61 static void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
62 				void *comp_opts)
63 {
64 	struct squashfs_stream *stream;
65 	struct decomp_stream *decomp_strm = NULL;
66 	int err = -ENOMEM;
67 
68 	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
69 	if (!stream)
70 		goto out;
71 
72 	stream->comp_opts = comp_opts;
73 	mutex_init(&stream->mutex);
74 	INIT_LIST_HEAD(&stream->strm_list);
75 	init_waitqueue_head(&stream->wait);
76 
77 	/*
78 	 * We should have a decompressor at least as default
79 	 * so if we fail to allocate new decompressor dynamically,
80 	 * we could always fall back to default decompressor and
81 	 * file system works.
82 	 */
83 	decomp_strm = kmalloc(sizeof(*decomp_strm), GFP_KERNEL);
84 	if (!decomp_strm)
85 		goto out;
86 
87 	decomp_strm->stream = msblk->decompressor->init(msblk,
88 						stream->comp_opts);
89 	if (IS_ERR(decomp_strm->stream)) {
90 		err = PTR_ERR(decomp_strm->stream);
91 		goto out;
92 	}
93 
94 	list_add(&decomp_strm->list, &stream->strm_list);
95 	stream->avail_decomp = 1;
96 	return stream;
97 
98 out:
99 	kfree(decomp_strm);
100 	kfree(stream);
101 	return ERR_PTR(err);
102 }
103 
104 
105 static void squashfs_decompressor_destroy(struct squashfs_sb_info *msblk)
106 {
107 	struct squashfs_stream *stream = msblk->stream;
108 	if (stream) {
109 		struct decomp_stream *decomp_strm;
110 
111 		while (!list_empty(&stream->strm_list)) {
112 			decomp_strm = list_entry(stream->strm_list.prev,
113 						struct decomp_stream, list);
114 			list_del(&decomp_strm->list);
115 			msblk->decompressor->free(decomp_strm->stream);
116 			kfree(decomp_strm);
117 			stream->avail_decomp--;
118 		}
119 		WARN_ON(stream->avail_decomp);
120 		kfree(stream->comp_opts);
121 		kfree(stream);
122 	}
123 }
124 
125 
126 static struct decomp_stream *get_decomp_stream(struct squashfs_sb_info *msblk,
127 					struct squashfs_stream *stream)
128 {
129 	struct decomp_stream *decomp_strm;
130 
131 	while (1) {
132 		mutex_lock(&stream->mutex);
133 
134 		/* There is available decomp_stream */
135 		if (!list_empty(&stream->strm_list)) {
136 			decomp_strm = list_entry(stream->strm_list.prev,
137 				struct decomp_stream, list);
138 			list_del(&decomp_strm->list);
139 			mutex_unlock(&stream->mutex);
140 			break;
141 		}
142 
143 		/*
144 		 * If there is no available decomp and already full,
145 		 * let's wait for releasing decomp from other users.
146 		 */
147 		if (stream->avail_decomp >= msblk->max_thread_num)
148 			goto wait;
149 
150 		/* Let's allocate new decomp */
151 		decomp_strm = kmalloc(sizeof(*decomp_strm), GFP_KERNEL);
152 		if (!decomp_strm)
153 			goto wait;
154 
155 		decomp_strm->stream = msblk->decompressor->init(msblk,
156 						stream->comp_opts);
157 		if (IS_ERR(decomp_strm->stream)) {
158 			kfree(decomp_strm);
159 			goto wait;
160 		}
161 
162 		stream->avail_decomp++;
163 		WARN_ON(stream->avail_decomp > msblk->max_thread_num);
164 
165 		mutex_unlock(&stream->mutex);
166 		break;
167 wait:
168 		/*
169 		 * If system memory is tough, let's for other's
170 		 * releasing instead of hurting VM because it could
171 		 * make page cache thrashing.
172 		 */
173 		mutex_unlock(&stream->mutex);
174 		wait_event(stream->wait,
175 			!list_empty(&stream->strm_list));
176 	}
177 
178 	return decomp_strm;
179 }
180 
181 
182 static int squashfs_decompress(struct squashfs_sb_info *msblk, struct bio *bio,
183 			int offset, int length,
184 			struct squashfs_page_actor *output)
185 {
186 	int res;
187 	struct squashfs_stream *stream = msblk->stream;
188 	struct decomp_stream *decomp_stream = get_decomp_stream(msblk, stream);
189 	res = msblk->decompressor->decompress(msblk, decomp_stream->stream,
190 		bio, offset, length, output);
191 	put_decomp_stream(decomp_stream, stream);
192 	if (res < 0)
193 		ERROR("%s decompression failed, data probably corrupt\n",
194 			msblk->decompressor->name);
195 	return res;
196 }
197 
198 const struct squashfs_decompressor_thread_ops squashfs_decompressor_multi = {
199 	.create = squashfs_decompressor_create,
200 	.destroy = squashfs_decompressor_destroy,
201 	.decompress = squashfs_decompress,
202 	.max_decompressors = squashfs_max_decompressors,
203 };
204