]> git.openfabrics.org - ~shefty/rdma-dev.git/blob - arch/um/drivers/cow_user.c
uml: cow_user.c warning corrections
[~shefty/rdma-dev.git] / arch / um / drivers / cow_user.c
1 /*
2  * Copyright (C) 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
3  * Licensed under the GPL
4  */
5
6 /*
7  * _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
8  * that.
9  */
10 #include <unistd.h>
11 #include <byteswap.h>
12 #include <errno.h>
13 #include <string.h>
14 #include <arpa/inet.h>
15 #include <asm/types.h>
16 #include "cow.h"
17 #include "cow_sys.h"
18
19 #define PATH_LEN_V1 256
20
21 typedef __u32 time32_t;
22
23 struct cow_header_v1 {
24         __s32 magic;
25         __s32 version;
26         char backing_file[PATH_LEN_V1];
27         time32_t mtime;
28         __u64 size;
29         __s32 sectorsize;
30 } __attribute__((packed));
31
32 /*
33  * Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
34  * case other systems have different values for MAXPATHLEN.
35  *
36  * The same must hold for V2 - we want file format compatibility, not anything
37  * else.
38  */
39 #define PATH_LEN_V3 4096
40 #define PATH_LEN_V2 PATH_LEN_V3
41
42 struct cow_header_v2 {
43         __u32 magic;
44         __u32 version;
45         char backing_file[PATH_LEN_V2];
46         time32_t mtime;
47         __u64 size;
48         __s32 sectorsize;
49 } __attribute__((packed));
50
51 /*
52  * Changes from V2 -
53  *      PATH_LEN_V3 as described above
54  *      Explicitly specify field bit lengths for systems with different
55  *              lengths for the usual C types.  Not sure whether char or
56  *              time_t should be changed, this can be changed later without
57  *              breaking compatibility
58  *      Add alignment field so that different alignments can be used for the
59  *              bitmap and data
60  *      Add cow_format field to allow for the possibility of different ways
61  *              of specifying the COW blocks.  For now, the only value is 0,
62  *              for the traditional COW bitmap.
63  *      Move the backing_file field to the end of the header.  This allows
64  *              for the possibility of expanding it into the padding required
65  *              by the bitmap alignment.
66  *      The bitmap and data portions of the file will be aligned as specified
67  *              by the alignment field.  This is to allow COW files to be
68  *              put on devices with restrictions on access alignments, such as
69  *              /dev/raw, with a 512 byte alignment restriction.  This also
70  *              allows the data to be more aligned more strictly than on
71  *              sector boundaries.  This is needed for ubd-mmap, which needs
72  *              the data to be page aligned.
73  *      Fixed (finally!) the rounding bug
74  */
75
76 /*
77  * Until Dec2005, __attribute__((packed)) was left out from the below
78  * definition, leading on 64-bit systems to 4 bytes of padding after mtime, to
79  * align size to 8-byte alignment.  This shifted all fields above (no padding
80  * was present on 32-bit, no other padding was added).
81  *
82  * However, this _can be detected_: it means that cow_format (always 0 until
83  * now) is shifted onto the first 4 bytes of backing_file, where it is otherwise
84  * impossible to find 4 zeros. -bb */
85
86 struct cow_header_v3 {
87         __u32 magic;
88         __u32 version;
89         __u32 mtime;
90         __u64 size;
91         __u32 sectorsize;
92         __u32 alignment;
93         __u32 cow_format;
94         char backing_file[PATH_LEN_V3];
95 } __attribute__((packed));
96
97 /* This is the broken layout used by some 64-bit binaries. */
98 struct cow_header_v3_broken {
99         __u32 magic;
100         __u32 version;
101         __s64 mtime;
102         __u64 size;
103         __u32 sectorsize;
104         __u32 alignment;
105         __u32 cow_format;
106         char backing_file[PATH_LEN_V3];
107 };
108
109 /* COW format definitions - for now, we have only the usual COW bitmap */
110 #define COW_BITMAP 0
111
112 union cow_header {
113         struct cow_header_v1 v1;
114         struct cow_header_v2 v2;
115         struct cow_header_v3 v3;
116         struct cow_header_v3_broken v3_b;
117 };
118
119 #define COW_MAGIC 0x4f4f4f4d  /* MOOO */
120 #define COW_VERSION 3
121
122 #define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
123 #define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
124
125 void cow_sizes(int version, __u64 size, int sectorsize, int align,
126                int bitmap_offset, unsigned long *bitmap_len_out,
127                int *data_offset_out)
128 {
129         if (version < 3) {
130                 *bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
131
132                 *data_offset_out = bitmap_offset + *bitmap_len_out;
133                 *data_offset_out = (*data_offset_out + sectorsize - 1) /
134                         sectorsize;
135                 *data_offset_out *= sectorsize;
136         }
137         else {
138                 *bitmap_len_out = DIV_ROUND(size, sectorsize);
139                 *bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
140
141                 *data_offset_out = bitmap_offset + *bitmap_len_out;
142                 *data_offset_out = ROUND_UP(*data_offset_out, align);
143         }
144 }
145
146 static int absolutize(char *to, int size, char *from)
147 {
148         char save_cwd[256], *slash;
149         int remaining;
150
151         if (getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
152                 cow_printf("absolutize : unable to get cwd - errno = %d\n",
153                            errno);
154                 return -1;
155         }
156         slash = strrchr(from, '/');
157         if (slash != NULL) {
158                 *slash = '\0';
159                 if (chdir(from)) {
160                         *slash = '/';
161                         cow_printf("absolutize : Can't cd to '%s' - "
162                                    "errno = %d\n", from, errno);
163                         return -1;
164                 }
165                 *slash = '/';
166                 if (getcwd(to, size) == NULL) {
167                         cow_printf("absolutize : unable to get cwd of '%s' - "
168                                "errno = %d\n", from, errno);
169                         return -1;
170                 }
171                 remaining = size - strlen(to);
172                 if (strlen(slash) + 1 > remaining) {
173                         cow_printf("absolutize : unable to fit '%s' into %d "
174                                "chars\n", from, size);
175                         return -1;
176                 }
177                 strcat(to, slash);
178         }
179         else {
180                 if (strlen(save_cwd) + 1 + strlen(from) + 1 > size) {
181                         cow_printf("absolutize : unable to fit '%s' into %d "
182                                "chars\n", from, size);
183                         return -1;
184                 }
185                 strcpy(to, save_cwd);
186                 strcat(to, "/");
187                 strcat(to, from);
188         }
189         if (chdir(save_cwd)) {
190                 cow_printf("absolutize : Can't cd to '%s' - "
191                            "errno = %d\n", save_cwd, errno);
192                 return -1;
193         }
194         return 0;
195 }
196
197 int write_cow_header(char *cow_file, int fd, char *backing_file,
198                      int sectorsize, int alignment, unsigned long long *size)
199 {
200         struct cow_header_v3 *header;
201         unsigned long modtime;
202         int err;
203
204         err = cow_seek_file(fd, 0);
205         if (err < 0) {
206                 cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
207                 goto out;
208         }
209
210         err = -ENOMEM;
211         header = cow_malloc(sizeof(*header));
212         if (header == NULL) {
213                 cow_printf("write_cow_header - failed to allocate COW V3 "
214                            "header\n");
215                 goto out;
216         }
217         header->magic = htonl(COW_MAGIC);
218         header->version = htonl(COW_VERSION);
219
220         err = -EINVAL;
221         if (strlen(backing_file) > sizeof(header->backing_file) - 1) {
222                 /* Below, %zd is for a size_t value */
223                 cow_printf("Backing file name \"%s\" is too long - names are "
224                            "limited to %zd characters\n", backing_file,
225                            sizeof(header->backing_file) - 1);
226                 goto out_free;
227         }
228
229         if (absolutize(header->backing_file, sizeof(header->backing_file),
230                       backing_file))
231                 goto out_free;
232
233         err = os_file_modtime(header->backing_file, &modtime);
234         if (err < 0) {
235                 cow_printf("write_cow_header - backing file '%s' mtime "
236                            "request failed, err = %d\n", header->backing_file,
237                            -err);
238                 goto out_free;
239         }
240
241         err = cow_file_size(header->backing_file, size);
242         if (err < 0) {
243                 cow_printf("write_cow_header - couldn't get size of "
244                            "backing file '%s', err = %d\n",
245                            header->backing_file, -err);
246                 goto out_free;
247         }
248
249         header->mtime = htonl(modtime);
250         header->size = htonll(*size);
251         header->sectorsize = htonl(sectorsize);
252         header->alignment = htonl(alignment);
253         header->cow_format = COW_BITMAP;
254
255         err = cow_write_file(fd, header, sizeof(*header));
256         if (err != sizeof(*header)) {
257                 cow_printf("write_cow_header - write of header to "
258                            "new COW file '%s' failed, err = %d\n", cow_file,
259                            -err);
260                 goto out_free;
261         }
262         err = 0;
263  out_free:
264         cow_free(header);
265  out:
266         return err;
267 }
268
269 int file_reader(__u64 offset, char *buf, int len, void *arg)
270 {
271         int fd = *((int *) arg);
272
273         return pread(fd, buf, len, offset);
274 }
275
276 /* XXX Need to sanity-check the values read from the header */
277
278 int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
279                     __u32 *version_out, char **backing_file_out,
280                     time_t *mtime_out, unsigned long long *size_out,
281                     int *sectorsize_out, __u32 *align_out,
282                     int *bitmap_offset_out)
283 {
284         union cow_header *header;
285         char *file;
286         int err, n;
287         unsigned long version, magic;
288
289         header = cow_malloc(sizeof(*header));
290         if (header == NULL) {
291                 cow_printf("read_cow_header - Failed to allocate header\n");
292                 return -ENOMEM;
293         }
294         err = -EINVAL;
295         n = (*reader)(0, (char *) header, sizeof(*header), arg);
296         if (n < offsetof(typeof(header->v1), backing_file)) {
297                 cow_printf("read_cow_header - short header\n");
298                 goto out;
299         }
300
301         magic = header->v1.magic;
302         if (magic == COW_MAGIC)
303                 version = header->v1.version;
304         else if (magic == ntohl(COW_MAGIC))
305                 version = ntohl(header->v1.version);
306         /* No error printed because the non-COW case comes through here */
307         else goto out;
308
309         *version_out = version;
310
311         if (version == 1) {
312                 if (n < sizeof(header->v1)) {
313                         cow_printf("read_cow_header - failed to read V1 "
314                                    "header\n");
315                         goto out;
316                 }
317                 *mtime_out = header->v1.mtime;
318                 *size_out = header->v1.size;
319                 *sectorsize_out = header->v1.sectorsize;
320                 *bitmap_offset_out = sizeof(header->v1);
321                 *align_out = *sectorsize_out;
322                 file = header->v1.backing_file;
323         }
324         else if (version == 2) {
325                 if (n < sizeof(header->v2)) {
326                         cow_printf("read_cow_header - failed to read V2 "
327                                    "header\n");
328                         goto out;
329                 }
330                 *mtime_out = ntohl(header->v2.mtime);
331                 *size_out = ntohll(header->v2.size);
332                 *sectorsize_out = ntohl(header->v2.sectorsize);
333                 *bitmap_offset_out = sizeof(header->v2);
334                 *align_out = *sectorsize_out;
335                 file = header->v2.backing_file;
336         }
337         /* This is very subtle - see above at union cow_header definition */
338         else if (version == 3 && (*((int*)header->v3.backing_file) != 0)) {
339                 if (n < sizeof(header->v3)) {
340                         cow_printf("read_cow_header - failed to read V3 "
341                                    "header\n");
342                         goto out;
343                 }
344                 *mtime_out = ntohl(header->v3.mtime);
345                 *size_out = ntohll(header->v3.size);
346                 *sectorsize_out = ntohl(header->v3.sectorsize);
347                 *align_out = ntohl(header->v3.alignment);
348                 if (*align_out == 0) {
349                         cow_printf("read_cow_header - invalid COW header, "
350                                    "align == 0\n");
351                 }
352                 *bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
353                 file = header->v3.backing_file;
354         }
355         else if (version == 3) {
356                 cow_printf("read_cow_header - broken V3 file with"
357                            " 64-bit layout - recovering content.\n");
358
359                 if (n < sizeof(header->v3_b)) {
360                         cow_printf("read_cow_header - failed to read V3 "
361                                    "header\n");
362                         goto out;
363                 }
364
365                 /*
366                  * this was used until Dec2005 - 64bits are needed to represent
367                  * 2038+. I.e. we can safely do this truncating cast.
368                  *
369                  * Additionally, we must use ntohl() instead of ntohll(), since
370                  * the program used to use the former (tested - I got mtime
371                  * mismatch "0 vs whatever").
372                  *
373                  * Ever heard about bug-to-bug-compatibility ? ;-) */
374                 *mtime_out = (time32_t) ntohl(header->v3_b.mtime);
375
376                 *size_out = ntohll(header->v3_b.size);
377                 *sectorsize_out = ntohl(header->v3_b.sectorsize);
378                 *align_out = ntohl(header->v3_b.alignment);
379                 if (*align_out == 0) {
380                         cow_printf("read_cow_header - invalid COW header, "
381                                    "align == 0\n");
382                 }
383                 *bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
384                 file = header->v3_b.backing_file;
385         }
386         else {
387                 cow_printf("read_cow_header - invalid COW version\n");
388                 goto out;
389         }
390         err = -ENOMEM;
391         *backing_file_out = cow_strdup(file);
392         if (*backing_file_out == NULL) {
393                 cow_printf("read_cow_header - failed to allocate backing "
394                            "file\n");
395                 goto out;
396         }
397         err = 0;
398  out:
399         cow_free(header);
400         return err;
401 }
402
403 int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
404                   int alignment, int *bitmap_offset_out,
405                   unsigned long *bitmap_len_out, int *data_offset_out)
406 {
407         unsigned long long size, offset;
408         char zero = 0;
409         int err;
410
411         err = write_cow_header(cow_file, fd, backing_file, sectorsize,
412                                alignment, &size);
413         if (err)
414                 goto out;
415
416         *bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
417         cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
418                   bitmap_len_out, data_offset_out);
419
420         offset = *data_offset_out + size - sizeof(zero);
421         err = cow_seek_file(fd, offset);
422         if (err < 0) {
423                 cow_printf("cow bitmap lseek failed : err = %d\n", -err);
424                 goto out;
425         }
426
427         /*
428          * does not really matter how much we write it is just to set EOF
429          * this also sets the entire COW bitmap
430          * to zero without having to allocate it
431          */
432         err = cow_write_file(fd, &zero, sizeof(zero));
433         if (err != sizeof(zero)) {
434                 cow_printf("Write of bitmap to new COW file '%s' failed, "
435                            "err = %d\n", cow_file, -err);
436                 if (err >= 0)
437                         err = -EINVAL;
438                 goto out;
439         }
440
441         return 0;
442  out:
443         return err;
444 }