aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/s390/char/hmcdrv_cache.c
blob: 4cda5ada143ac810eb4832085826233b739ec136 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
/*
 *    SE/HMC Drive (Read) Cache Functions
 *
 *    Copyright IBM Corp. 2013
 *    Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
 *
 */

#define KMSG_COMPONENT "hmcdrv"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/jiffies.h>

#include "hmcdrv_ftp.h"
#include "hmcdrv_cache.h"

#define HMCDRV_CACHE_TIMEOUT		30 /* aging timeout in seconds */

/**
 * struct hmcdrv_cache_entry - file cache (only used on read/dir)
 * @id: FTP command ID
 * @content: kernel-space buffer, 4k aligned
 * @len: size of @content cache (0 if caching disabled)
 * @ofs: start of content within file (-1 if no cached content)
 * @fname: file name
 * @fsize: file size
 * @timeout: cache timeout in jiffies
 *
 * Notice that the first three members (id, fname, fsize) are cached on all
 * read/dir requests. But content is cached only under some preconditions.
 * Uncached content is signalled by a negative value of @ofs.
 */
struct hmcdrv_cache_entry {
	enum hmcdrv_ftp_cmdid id;
	char fname[HMCDRV_FTP_FIDENT_MAX];
	size_t fsize;
	loff_t ofs;
	unsigned long timeout;
	void *content;
	size_t len;
};

static int hmcdrv_cache_order; /* cache allocated page order */

static struct hmcdrv_cache_entry hmcdrv_cache_file = {
	.fsize = SIZE_MAX,
	.ofs = -1,
	.len = 0,
	.fname = {'\0'}
};

/**
 * hmcdrv_cache_get() - looks for file data/content in read cache
 * @ftp: pointer to FTP command specification
 *
 * Return: number of bytes read from cache or a negative number if nothing
 * in content cache (for the file/cmd specified in @ftp)
 */
static ssize_t hmcdrv_cache_get(const struct hmcdrv_ftp_cmdspec *ftp)
{
	loff_t pos; /* position in cache (signed) */
	ssize_t len;

	if ((ftp->id != hmcdrv_cache_file.id) ||
	    strcmp(hmcdrv_cache_file.fname, ftp->fname))
		return -1;

	if (ftp->ofs >= hmcdrv_cache_file.fsize) /* EOF ? */
		return 0;

	if ((hmcdrv_cache_file.ofs < 0) || /* has content? */
	    time_after(jiffies, hmcdrv_cache_file.timeout))
		return -1;

	/* there seems to be cached content - calculate the maximum number
	 * of bytes that can be returned (regarding file size and offset)
	 */
	len = hmcdrv_cache_file.fsize - ftp->ofs;

	if (len > ftp->len)
		len = ftp->len;

	/* check if the requested chunk falls into our cache (which starts
	 * at offset 'hmcdrv_cache_file.ofs' in the file of interest)
	 */
	pos = ftp->ofs - hmcdrv_cache_file.ofs;

	if ((pos >= 0) &&
	    ((pos + len) <= hmcdrv_cache_file.len)) {

		memcpy(ftp->buf,
		       hmcdrv_cache_file.content + pos,
		       len);
		pr_debug("using cached content of '%s', returning %zd/%zd bytes\n",
			 hmcdrv_cache_file.fname, len,
			 hmcdrv_cache_file.fsize);

		return len;
	}

	return -1;
}

/**
 * hmcdrv_cache_do() - do a HMC drive CD/DVD transfer with cache update
 * @ftp: pointer to FTP command specification
 * @func: FTP transfer function to be used
 *
 * Return: number of bytes read/written or a (negative) error code
 */
static ssize_t hmcdrv_cache_do(const struct hmcdrv_ftp_cmdspec *ftp,
			       hmcdrv_cache_ftpfunc func)
{
	ssize_t len;

	/* only cache content if the read/dir cache really exists
	 * (hmcdrv_cache_file.len > 0), is large enough to handle the
	 * request (hmcdrv_cache_file.len >= ftp->len) and there is a need
	 * to do so (ftp->len > 0)
	 */
	if ((ftp->len > 0) && (hmcdrv_cache_file.len >= ftp->len)) {

		/* because the cache is not located at ftp->buf, we have to
		 * assemble a new HMC drive FTP cmd specification (pointing
		 * to our cache, and using the increased size)
		 */
		struct hmcdrv_ftp_cmdspec cftp = *ftp; /* make a copy */
		cftp.buf = hmcdrv_cache_file.content;  /* and update */
		cftp.len = hmcdrv_cache_file.len;      /* buffer data */

		len = func(&cftp, &hmcdrv_cache_file.fsize); /* now do */

		if (len > 0) {
			pr_debug("caching %zd bytes content for '%s'\n",
				 len, ftp->fname);

			if (len > ftp->len)
				len = ftp->len;

			hmcdrv_cache_file.ofs = ftp->ofs;
			hmcdrv_cache_file.timeout = jiffies +
				HMCDRV_CACHE_TIMEOUT * HZ;
			memcpy(ftp->buf, hmcdrv_cache_file.content, len);
		}
	} else {
		len = func(ftp, &hmcdrv_cache_file.fsize);
		hmcdrv_cache_file.ofs = -1; /* invalidate content */
	}

	if (len > 0) {
		/* cache some file info (FTP command, file name and file
		 * size) unconditionally
		 */
		strlcpy(hmcdrv_cache_file.fname, ftp->fname,
			HMCDRV_FTP_FIDENT_MAX);
		hmcdrv_cache_file.id = ftp->id;
		pr_debug("caching cmd %d, file size %zu for '%s'\n",
			 ftp->id, hmcdrv_cache_file.fsize, ftp->fname);
	}

	return len;
}

/**
 * hmcdrv_cache_cmd() - perform a cached HMC drive CD/DVD transfer
 * @ftp: pointer to FTP command specification
 * @func: FTP transfer function to be used
 *
 * Attention: Notice that this function is not reentrant - so the caller
 * must ensure exclusive execution.
 *
 * Return: number of bytes read/written or a (negative) error code
 */
ssize_t hmcdrv_cache_cmd(const struct hmcdrv_ftp_cmdspec *ftp,
			 hmcdrv_cache_ftpfunc func)
{
	ssize_t len;

	if ((ftp->id == HMCDRV_FTP_DIR) || /* read cache */
	    (ftp->id == HMCDRV_FTP_NLIST) ||
	    (ftp->id == HMCDRV_FTP_GET)) {

		len = hmcdrv_cache_get(ftp);

		if (len >= 0) /* got it from cache ? */
			return len; /* yes */

		len = hmcdrv_cache_do(ftp, func);

		if (len >= 0)
			return len;

	} else {
		len = func(ftp, NULL); /* simply do original command */
	}

	/* invalidate the (read) cache in case there was a write operation
	 * or an error on read/dir
	 */
	hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
	hmcdrv_cache_file.fsize = LLONG_MAX;
	hmcdrv_cache_file.ofs = -1;

	return len;
}

/**
 * hmcdrv_cache_startup() - startup of HMC drive cache
 * @cachesize: cache size
 *
 * Return: 0 on success, else a (negative) error code
 */
int hmcdrv_cache_startup(size_t cachesize)
{
	if (cachesize > 0) { /* perform caching ? */
		hmcdrv_cache_order = get_order(cachesize);
		hmcdrv_cache_file.content =
			(void *) __get_free_pages(GFP_KERNEL | GFP_DMA,
						  hmcdrv_cache_order);

		if (!hmcdrv_cache_file.content) {
			pr_err("Allocating the requested cache size of %zu bytes failed\n",
			       cachesize);
			return -ENOMEM;
		}

		pr_debug("content cache enabled, size is %zu bytes\n",
			 cachesize);
	}

	hmcdrv_cache_file.len = cachesize;
	return 0;
}

/**
 * hmcdrv_cache_shutdown() - shutdown of HMC drive cache
 */
void hmcdrv_cache_shutdown(void)
{
	if (hmcdrv_cache_file.content) {
		free_pages((unsigned long) hmcdrv_cache_file.content,
			   hmcdrv_cache_order);
		hmcdrv_cache_file.content = NULL;
	}

	hmcdrv_cache_file.id = HMCDRV_FTP_NOOP;
	hmcdrv_cache_file.fsize = LLONG_MAX;
	hmcdrv_cache_file.ofs = -1;
	hmcdrv_cache_file.len = 0; /* no cache */
}