save.c revision 0a84e9cae698b8ea5c3389429126c25816986d81 
1/*
2 * save.c - write the cache struct to disk
3 *
4 * Copyright (C) 2001 by Andreas Dilger
5 * Copyright (C) 2003 Theodore Ts'o
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the
9 * GNU Lesser General Public License.
10 * %End-Header%
11 */
12
13#include <stdio.h>
14#include <string.h>
15#include <stdlib.h>
16#include <unistd.h>
17#include <sys/types.h>
18#ifdef HAVE_SYS_STAT_H
19#include <sys/stat.h>
20#endif
21#ifdef HAVE_SYS_MKDEV_H
22#include <sys/mkdev.h>
23#endif
24#ifdef HAVE_ERRNO_H
25#include <errno.h>
26#endif
27#include "blkidP.h"
28
29static int save_dev(blkid_dev dev, FILE *file)
30{
31	struct list_head *p;
32
33	if (!dev || dev->bid_name[0] != '/')
34		return 0;
35
36	DBG(DEBUG_SAVE,
37	    printf("device %s, type %s\n", dev->bid_name, dev->bid_type));
38
39	fprintf(file,
40		"<device DEVNO=\"0x%04lx\" TIME=\"%ld\"",
41		(unsigned long) dev->bid_devno, (long) dev->bid_time);
42	if (dev->bid_pri)
43		fprintf(file, " PRI=\"%d\"", dev->bid_pri);
44	list_for_each(p, &dev->bid_tags) {
45		blkid_tag tag = list_entry(p, struct blkid_struct_tag, bit_tags);
46		fprintf(file, " %s=\"%s\"", tag->bit_name,tag->bit_val);
47	}
48	fprintf(file, ">%s</device>\n", dev->bid_name);
49
50	return 0;
51}
52
53/*
54 * Write out the cache struct to the cache file on disk.
55 */
56int blkid_flush_cache(blkid_cache cache)
57{
58	struct list_head *p;
59	char *tmp = NULL;
60	const char *opened = NULL;
61	const char *filename;
62	FILE *file = NULL;
63	int fd, ret = 0;
64	struct stat st;
65
66	if (!cache)
67		return -BLKID_ERR_PARAM;
68
69	if (list_empty(&cache->bic_devs) ||
70	    !(cache->bic_flags & BLKID_BIC_FL_CHANGED)) {
71		DBG(DEBUG_SAVE, printf("skipping cache file write\n"));
72		return 0;
73	}
74
75	filename = cache->bic_filename ? cache->bic_filename: BLKID_CACHE_FILE;
76
77	/* If we can't write to the cache file, then don't even try */
78	if (((ret = stat(filename, &st)) < 0 && errno != ENOENT) ||
79	    (ret == 0 && access(filename, W_OK) < 0)) {
80		DBG(DEBUG_SAVE,
81		    printf("can't write to cache file %s\n", filename));
82		return 0;
83	}
84
85	/*
86	 * Try and create a temporary file in the same directory so
87	 * that in case of error we don't overwrite the cache file.
88	 * If the cache file doesn't yet exist, it isn't a regular
89	 * file (e.g. /dev/null or a socket), or we couldn't create
90	 * a temporary file then we open it directly.
91	 */
92	if (ret == 0 && S_ISREG(st.st_mode)) {
93		tmp = malloc(strlen(filename) + 8);
94		if (tmp) {
95			sprintf(tmp, "%s-XXXXXX", filename);
96			fd = mkstemp(tmp);
97			if (fd >= 0) {
98				file = fdopen(fd, "w");
99				opened = tmp;
100			}
101			fchmod(fd, 0644);
102		}
103	}
104
105	if (!file) {
106		file = fopen(filename, "w");
107		opened = filename;
108	}
109
110	DBG(DEBUG_SAVE,
111	    printf("writing cache file %s (really %s)\n",
112		   filename, opened));
113
114	if (!file) {
115		ret = errno;
116		goto errout;
117	}
118
119	list_for_each(p, &cache->bic_devs) {
120		blkid_dev dev = list_entry(p, struct blkid_struct_dev, bid_devs);
121		if (!dev->bid_type)
122			continue;
123		if ((ret = save_dev(dev, file)) < 0)
124			break;
125	}
126
127	if (ret >= 0) {
128		cache->bic_flags &= ~BLKID_BIC_FL_CHANGED;
129		ret = 1;
130	}
131
132	fclose(file);
133	if (opened != filename) {
134		if (ret < 0) {
135			unlink(opened);
136			DBG(DEBUG_SAVE,
137			    printf("unlinked temp cache %s\n", opened));
138		} else {
139			char *backup;
140
141			backup = malloc(strlen(filename) + 5);
142			if (backup) {
143				sprintf(backup, "%s.old", filename);
144				unlink(backup);
145				link(filename, backup);
146				free(backup);
147			}
148			rename(opened, filename);
149			DBG(DEBUG_SAVE,
150			    printf("moved temp cache %s\n", opened));
151		}
152	}
153
154errout:
155	if (tmp)
156		free(tmp);
157	return ret;
158}
159
160#ifdef TEST_PROGRAM
161int main(int argc, char **argv)
162{
163	blkid_cache cache = NULL;
164	int ret;
165
166	blkid_debug_mask = DEBUG_ALL;
167	if (argc > 2) {
168		fprintf(stderr, "Usage: %s [filename]\n"
169			"Test loading/saving a cache (filename)\n", argv[0]);
170		exit(1);
171	}
172
173	if ((ret = blkid_get_cache(&cache, "/dev/null")) != 0) {
174		fprintf(stderr, "%s: error creating cache (%d)\n",
175			argv[0], ret);
176		exit(1);
177	}
178	if ((ret = blkid_probe_all(cache)) < 0) {
179		fprintf(stderr, "error (%d) probing devices\n", ret);
180		exit(1);
181	}
182	cache->bic_filename = blkid_strdup(argv[1]);
183
184	if ((ret = blkid_flush_cache(cache)) < 0) {
185		fprintf(stderr, "error (%d) saving cache\n", ret);
186		exit(1);
187	}
188
189	blkid_put_cache(cache);
190
191	return ret;
192}
193#endif
194