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make-bcache: Prevent stray superblocks

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Fail if the device has any leftover superblock or partition table label.

Add a --wipe-bcache flag to overwrite bcache superblocks and recommend
wipefs for non-bcache superblocks.

Once the device is safe to write, always zero immediately before the
bcache superblock.

Make sure errors go to stderr.  Use pkg-config.
This commit is contained in:
Gabriel 2013-08-17 18:56:50 +02:00
parent 8327108eea
commit b15fb776c9
3 changed files with 59 additions and 23 deletions
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9
Makefile
View File

@ -16,9 +16,10 @@ install: make-bcache probe-bcache bcache-super-show
clean:
$(RM) -f make-bcache probe-bcache bcache-super-show bcache-test *.o
bcache-test: LDLIBS += -lm -lssl -lcrypto
make-bcache: LDLIBS += -luuid
bcache-test: LDLIBS += `pkg-config --libs openssl`
make-bcache: LDLIBS += `pkg-config --libs uuid blkid`
make-bcache: CFLAGS += `pkg-config --cflags uuid blkid`
make-bcache: bcache.o
probe-bcache: LDLIBS += -luuid
bcache-super-show: LDLIBS += -luuid
probe-bcache: LDLIBS += `pkg-config --libs uuid`
bcache-super-show: LDLIBS += `pkg-config --libs uuid`
bcache-super-show: bcache.o

71
make-bcache.c
View File

@ -8,6 +8,7 @@
#define __USE_FILE_OFFSET64
#define _XOPEN_SOURCE 600
#include <blkid.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
@ -76,19 +77,19 @@ unsigned hatoi_validate(const char *s, const char *msg)
uint64_t v = hatoi(s);
if (v & (v - 1)) {
printf("%s must be a power of two\n", msg);
fprintf(stderr, "%s must be a power of two\n", msg);
exit(EXIT_FAILURE);
}
v /= 512;
if (v > USHRT_MAX) {
printf("%s too large\n", msg);
fprintf(stderr, "%s too large\n", msg);
exit(EXIT_FAILURE);
}
if (!v) {
printf("%s too small\n", msg);
fprintf(stderr, "%s too small\n", msg);
exit(EXIT_FAILURE);
}
@ -143,7 +144,8 @@ ssize_t read_string_list(const char *buf, const char * const list[])
void usage()
{
printf("Usage: make-bcache [options] device\n"
fprintf(stderr,
"Usage: make-bcache [options] device\n"
" -C, --cache Format a cache device\n"
" -B, --bdev Format a backing device\n"
" -b, --bucket bucket size\n"
@ -166,17 +168,41 @@ const char * const cache_replacement_policies[] = {
};
static void write_sb(char *dev, unsigned block_size, unsigned bucket_size,
bool writeback, bool discard,
bool writeback, bool discard, bool wipe_bcache,
unsigned cache_replacement_policy,
uint64_t data_offset,
uuid_t set_uuid, bool bdev)
{
int fd;
char uuid_str[40], set_uuid_str[40];
char uuid_str[40], set_uuid_str[40], zeroes[SB_START] = {0};
struct cache_sb sb;
blkid_probe pr;
if ((fd = open(dev, O_RDWR|O_EXCL)) == -1) {
printf("Can't open dev %s: %s\n", dev, strerror(errno));
fprintf(stderr, "Can't open dev %s: %s\n", dev, strerror(errno));
exit(EXIT_FAILURE);
}
if (pread(fd, &sb, sizeof(sb), SB_START) != sizeof(sb))
exit(EXIT_FAILURE);
if (!memcmp(sb.magic, bcache_magic, 16) && !wipe_bcache) {
fprintf(stderr, "Already a bcache device on %s, "
"overwrite with --wipe-bcache\n", dev);
exit(EXIT_FAILURE);
}
if (!(pr = blkid_new_probe()))
exit(EXIT_FAILURE);
if (blkid_probe_set_device(pr, fd, 0, 0))
exit(EXIT_FAILURE);
/* enable ptable probing; superblock probing is enabled by default */
if (blkid_probe_enable_partitions(pr, true))
exit(EXIT_FAILURE);
if (!blkid_do_probe(pr)) {
/* XXX wipefs doesn't know how to remove partition tables */
fprintf(stderr, "Device %s already has a non-bcache superblock, "
"remove it using wipefs and wipefs -a\n", dev);
exit(EXIT_FAILURE);
}
@ -221,7 +247,7 @@ static void write_sb(char *dev, unsigned block_size, unsigned bucket_size,
sb.first_bucket = (23 / sb.bucket_size) + 1;
if (sb.nbuckets < 1 << 7) {
printf("Not enough buckets: %ju, need %u\n",
fprintf(stderr, "Not enough buckets: %ju, need %u\n",
sb.nbuckets, 1 << 7);
exit(EXIT_FAILURE);
}
@ -250,7 +276,13 @@ static void write_sb(char *dev, unsigned block_size, unsigned bucket_size,
sb.csum = csum_set(&sb);
if (pwrite(fd, &sb, sizeof(sb), SB_SECTOR << 9) != sizeof(sb)) {
/* Zero start of disk */
if (pwrite(fd, zeroes, SB_START, 0) != SB_START) {
perror("write error\n");
exit(EXIT_FAILURE);
}
/* Write superblock */
if (pwrite(fd, &sb, sizeof(sb), SB_START) != sizeof(sb)) {
perror("write error\n");
exit(EXIT_FAILURE);
}
@ -311,7 +343,7 @@ int main(int argc, char **argv)
char *backing_devices[argc];
unsigned block_size = 0, bucket_size = 1024;
int writeback = 0, discard = 0;
int writeback = 0, discard = 0, wipe_bcache = 0;
unsigned cache_replacement_policy = 0;
uint64_t data_offset = BDEV_DATA_START_DEFAULT;
uuid_t set_uuid;
@ -324,6 +356,7 @@ int main(int argc, char **argv)
{ "bucket", 1, NULL, 'b' },
{ "block", 1, NULL, 'w' },
{ "writeback", 0, &writeback, 1 },
{ "wipe-bcache", 0, &wipe_bcache, 1 },
{ "discard", 0, &discard, 1 },
{ "cache_replacement_policy", 1, NULL, 'p' },
{ "data_offset", 1, NULL, 'o' },
@ -351,7 +384,7 @@ int main(int argc, char **argv)
#if 0
case 'U':
if (uuid_parse(optarg, sb.uuid)) {
printf("Bad uuid\n");
fprintf(stderr, "Bad uuid\n");
exit(EXIT_FAILURE);
}
break;
@ -363,14 +396,14 @@ int main(int argc, char **argv)
case 'o':
data_offset = atoll(optarg);
if (data_offset < BDEV_DATA_START_DEFAULT) {
printf("Bad data offset; minimum %d sectors\n",
fprintf(stderr, "Bad data offset; minimum %d sectors\n",
BDEV_DATA_START_DEFAULT);
exit(EXIT_FAILURE);
}
break;
case 'u':
if (uuid_parse(optarg, set_uuid)) {
printf("Bad uuid\n");
fprintf(stderr, "Bad uuid\n");
exit(EXIT_FAILURE);
}
break;
@ -379,7 +412,7 @@ int main(int argc, char **argv)
break;
case 1:
if (bdev == -1) {
printf("Please specify -C or -B\n");
fprintf(stderr, "Please specify -C or -B\n");
exit(EXIT_FAILURE);
}
@ -391,12 +424,12 @@ int main(int argc, char **argv)
}
if (!ncache_devices && !nbacking_devices) {
printf("Please supply a device\n");
fprintf(stderr, "Please supply a device\n");
usage();
}
if (bucket_size < block_size) {
printf("Bucket size cannot be smaller than block size\n");
fprintf(stderr, "Bucket size cannot be smaller than block size\n");
exit(EXIT_FAILURE);
}
@ -412,12 +445,14 @@ int main(int argc, char **argv)
for (i = 0; i < ncache_devices; i++)
write_sb(cache_devices[i], block_size, bucket_size,
writeback, discard, cache_replacement_policy,
writeback, discard, wipe_bcache,
cache_replacement_policy,
data_offset, set_uuid, false);
for (i = 0; i < nbacking_devices; i++)
write_sb(backing_devices[i], block_size, bucket_size,
writeback, discard, cache_replacement_policy,
writeback, discard, wipe_bcache,
cache_replacement_policy,
data_offset, set_uuid, true);
return 0;

2
probe-bcache.c
View File

@ -52,7 +52,7 @@ int main(int argc, char **argv)
continue;
if (pread(fd, &sb, sizeof(sb), 4096) != sizeof(sb))
if (pread(fd, &sb, sizeof(sb), SB_START) != sizeof(sb))
continue;
if (memcmp(sb.magic, bcache_magic, 16))