1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * SE/HMC Drive (Read) Cache Functions
4 *
5 * Copyright IBM Corp. 2013
6 * Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
7 *
8 */
9
10 #define KMSG_COMPONENT "hmcdrv"
11 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
12
13 #include <linux/kernel.h>
14 #include <linux/mm.h>
15 #include <linux/jiffies.h>
16
17 #include "hmcdrv_ftp.h"
18 #include "hmcdrv_cache.h"
19
20 #define HMCDRV_CACHE_TIMEOUT 30 /* aging timeout in seconds */
21
22 /**
23 * struct hmcdrv_cache_entry - file cache (only used on read/dir)
24 * @id: FTP command ID
25 * @content: kernel-space buffer, 4k aligned
26 * @len: size of @content cache (0 if caching disabled)
27 * @ofs: start of content within file (-1 if no cached content)
28 * @fname: file name
29 * @fsize: file size
30 * @timeout: cache timeout in jiffies
31 *
32 * Notice that the first three members (id, fname, fsize) are cached on all
33 * read/dir requests. But content is cached only under some preconditions.
34 * Uncached content is signalled by a negative value of @ofs.
35 */
36 struct hmcdrv_cache_entry {
37 enum hmcdrv_ftp_cmdid id;
38 char fname[HMCDRV_FTP_FIDENT_MAX];
39 size_t fsize;
40 loff_t ofs;
41 unsigned long timeout;
42 void *content;
43 size_t len;
44 };
45
46 static int hmcdrv_cache_order; /* cache allocated page order */
47
48 static struct hmcdrv_cache_entry hmcdrv_cache_file = {
49 .fsize = SIZE_MAX,
50 .ofs = -1,
51 .len = 0,
52 .fname = {'\0'}
53 };
54
55 /**
56 * hmcdrv_cache_get() - looks for file data/content in read cache
57 * @ftp: pointer to FTP command specification
58 *
59 * Return: number of bytes read from cache or a negative number if nothing
60 * in content cache (for the file/cmd specified in @ftp)
61 */
62 static ssize_t hmcdrv_cache_get(const struct hmcdrv_ftp_cmdspec *ftp)
63 {
64 loff_t pos; /* position in cache (signed) */
65 ssize_t len;
66
67 if ((ftp->id != hmcdrv_cache_file.id) ||
68 strcmp(hmcdrv_cache_file.fname, ftp->fname))
69 return -1;
70
71 if (ftp->ofs >= hmcdrv_cache_file.fsize) /* EOF ? */
72 return 0;
73
74 if ((hmcdrv_cache_file.ofs < 0) || /* has content? */
75 time_after(jiffies, hmcdrv_cache_file.timeout))
76 return -1;
77
78 /* there seems to be cached content - calculate the maximum number
79 * of bytes that can be returned (regarding file size and offset)
80 */
81 len = hmcdrv_cache_file.fsize - ftp->ofs;
82
83 if (len > ftp->len)
84 len = ftp->len;
85
86 /* check if the requested chunk falls into our cache (which starts
87 * at offset 'hmcdrv_cache_file.ofs' in the file of interest)
88 */
89 pos = ftp->ofs - hmcdrv_cache_file.ofs;
90
91 if ((pos >= 0) &&
92 ((pos + len) <= hmcdrv_cache_file.len)) {
93
94 memcpy(ftp->buf,
95 hmcdrv_cache_file.content + pos,
96 len);
97 pr_debug("using cached content of '%s', returning %zd/%zd bytes\n",
98 hmcdrv_cache_file.fname, len,
99 hmcdrv_cache_file.fsize);
100
101 return len;
102 }
103
104 return -1;
105 }
106
107 /**
108 * hmcdrv_cache_do() - do a HMC drive CD/DVD transfer with cache update
109 * @ftp: pointer to FTP command specification
110 * @func: FTP transfer function to be used
111 *
112 * Return: number of bytes read/written or a (negative) error code
113 */
114 static ssize_t hmcdrv_cache_do(const struct hmcdrv_ftp_cmdspec *ftp,
115 hmcdrv_cache_ftpfunc func)
116 {
117 ssize_t len;
118
119 /* only cache content if the read/dir cache really exists
120 * (hmcdrv_cache_file.len > 0), is large enough to handle the
121 * request (hmcdrv_cache_file.len >= ftp->len) and there is a need
122 * to do so (ftp->len > 0)
123 */
124 if ((ftp->len > 0) && (hmcdrv_cache_file.len >= ftp->len)) {
125
126 /* because the cache is not located at ftp->buf, we have to
127 * assemble a new HMC drive FTP cmd specification (pointing
128 * to our cache, and using the increased size)
129 */
130 struct hmcdrv_ftp_cmdspec cftp = *ftp; /* make a copy */
131 cftp.buf = hmcdrv_cache_file.content; /* and update */
132 cftp.len = hmcdrv_cache_file.len; /* buffer data */
133
134 len = func(&cftp, &hmcdrv_cache_file.fsize); /* now do */
135
136 if (len > 0) {
137 pr_debug("caching %zd bytes content for '%s'\n",
138 len, ftp->fname);
139
140 if (len > ftp->len)
141 len = ftp->len;
142
143 hmcdrv_cache_file.ofs = ftp->ofs;
144 hmcdrv_cache_file.timeout = jiffies +
145 HMCDRV_CACHE_TIMEOUT * HZ;
146 memcpy(ftp->buf, hmcdrv_cache_file.content, len);
147 }
148 } else {
149 len = func(ftp, &hmcdrv_cache_file.fsize);
150 hmcdrv_cache_file.ofs = -1; /* invalidate content */
151 }
152
153 if (len > 0) {
154 /* cache some file info (FTP command, file name and file
155 * size) unconditionally
156 */
157 strlcpy(hmcdrv_cache_file.fname, ftp->fname,
158 HMCDRV_FTP_FIDENT_MAX);
159 hmcdrv_cache_file.id = ftp->id;
160 pr_debug("caching cmd %d, file size %zu for '%s'\n",
161 ftp->id, hmcdrv_cache_file.fsize, ftp->fname);
162 }
163
164 return len;
165 }
166
167 /**
168 * hmcdrv_cache_cmd() - perform a cached HMC drive CD/DVD transfer
169 * @ftp: pointer to FTP command specification
170 * @func: FTP transfer function to be used
171 *
172 * Attention: Notice that this function is not reentrant - so the caller
173 * must ensure exclusive execution.
174 *
175 * Return: number of bytes read/written or a (negative) error code
176 */
177 ssize_t hmcdrv_cache_cmd(const struct hmcdrv_ftp_cmdspec *ftp,
178 hmcdrv_cache_ftpfunc func)
179 {
180 ssize_t len;
181
182 if ((ftp->id == HMCDRV_FTP_DIR) || /* read cache */
183 (ftp->id == HMCDRV_FTP_NLIST) ||
184 (ftp->id == HMCDRV_FTP_GET)) {
185
186 len = hmcdrv_cache_get(ftp);
187
188 if (len >= 0) /* got it from cache ? */
189 return len; /* yes */
190
191 len = hmcdrv_cache_do(ftp, func);
192
193 if (len >= 0)
194 return len;
195
196 } else {
197 len = func(ftp, NULL); /* simply do original command */
198 }
199
200 /* invalidate the (read) cache in case there was a write operation
201 * or an error on read/dir
202 */
203 hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
204 hmcdrv_cache_file.fsize = LLONG_MAX;
205 hmcdrv_cache_file.ofs = -1;
206
207 return len;
208 }
209
210 /**
211 * hmcdrv_cache_startup() - startup of HMC drive cache
212 * @cachesize: cache size
213 *
214 * Return: 0 on success, else a (negative) error code
215 */
216 int hmcdrv_cache_startup(size_t cachesize)
217 {
218 if (cachesize > 0) { /* perform caching ? */
219 hmcdrv_cache_order = get_order(cachesize);
220 hmcdrv_cache_file.content =
221 (void *) __get_free_pages(GFP_KERNEL | GFP_DMA,
222 hmcdrv_cache_order);
223
224 if (!hmcdrv_cache_file.content) {
225 pr_err("Allocating the requested cache size of %zu bytes failed\n",
226 cachesize);
227 return -ENOMEM;
228 }
229
230 pr_debug("content cache enabled, size is %zu bytes\n",
231 cachesize);
232 }
233
234 hmcdrv_cache_file.len = cachesize;
235 return 0;
236 }
237
238 /**
239 * hmcdrv_cache_shutdown() - shutdown of HMC drive cache
240 */
241 void hmcdrv_cache_shutdown(void)
242 {
243 if (hmcdrv_cache_file.content) {
244 free_pages((unsigned long) hmcdrv_cache_file.content,
245 hmcdrv_cache_order);
246 hmcdrv_cache_file.content = NULL;
247 }
248
249 hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
250 hmcdrv_cache_file.fsize = LLONG_MAX;
251 hmcdrv_cache_file.ofs = -1;
252 hmcdrv_cache_file.len = 0; /* no cache */
253 }