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bcachefs: Split brain detection

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Use the new bch_member->seq, sb->write_time fields to detect split brain
and kick out devices when necessary.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-06-27 21:02:27 -04:00
parent 6b00de06f5
commit 0d529663f0
2 changed files with 65 additions and 11 deletions
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1
fs/bcachefs/errcode.h
View File

@ -170,6 +170,7 @@
x(EINVAL, device_size_too_small) \
x(EINVAL, device_not_a_member_of_filesystem) \
x(EINVAL, device_has_been_removed) \
x(EINVAL, device_splitbrain) \
x(EINVAL, device_already_online) \
x(EINVAL, insufficient_devices_to_start) \
x(EINVAL, invalid) \

75
fs/bcachefs/super.c
View File

@ -1063,20 +1063,65 @@ static int bch2_dev_may_add(struct bch_sb *sb, struct bch_fs *c)
return 0;
}
static int bch2_dev_in_fs(struct bch_sb *fs, struct bch_sb *sb)
static int bch2_dev_in_fs(struct bch_sb_handle *fs,
struct bch_sb_handle *sb)
{
struct bch_sb *newest =
le64_to_cpu(fs->seq) > le64_to_cpu(sb->seq) ? fs : sb;
if (fs == sb)
return 0;
if (!uuid_equal(&fs->uuid, &sb->uuid))
if (!uuid_equal(&fs->sb->uuid, &sb->sb->uuid))
return -BCH_ERR_device_not_a_member_of_filesystem;
if (!bch2_dev_exists(newest, sb->dev_idx))
if (!bch2_dev_exists(fs->sb, sb->sb->dev_idx))
return -BCH_ERR_device_has_been_removed;
if (fs->block_size != sb->block_size)
if (fs->sb->block_size != sb->sb->block_size)
return -BCH_ERR_mismatched_block_size;
if (le16_to_cpu(fs->sb->version) < bcachefs_metadata_version_member_seq ||
le16_to_cpu(sb->sb->version) < bcachefs_metadata_version_member_seq)
return 0;
if (fs->sb->seq == sb->sb->seq &&
fs->sb->write_time != sb->sb->write_time) {
struct printbuf buf = PRINTBUF;
prt_printf(&buf, "Split brain detected between %pg and %pg:",
sb->bdev, fs->bdev);
prt_newline(&buf);
prt_printf(&buf, "seq=%llu but write_time different, got", le64_to_cpu(sb->sb->seq));
prt_newline(&buf);
prt_printf(&buf, "%pg ", fs->bdev);
bch2_prt_datetime(&buf, le64_to_cpu(fs->sb->write_time));;
prt_newline(&buf);
prt_printf(&buf, "%pg ", sb->bdev);
bch2_prt_datetime(&buf, le64_to_cpu(sb->sb->write_time));;
prt_newline(&buf);
prt_printf(&buf, "Not using older sb");
pr_err("%s", buf.buf);
printbuf_exit(&buf);
return -BCH_ERR_device_splitbrain;
}
struct bch_member m = bch2_sb_member_get(fs->sb, sb->sb->dev_idx);
u64 seq_from_fs = le64_to_cpu(m.seq);
u64 seq_from_member = le64_to_cpu(sb->sb->seq);
if (seq_from_fs && seq_from_fs < seq_from_member) {
pr_err("Split brain detected between %pg and %pg:\n"
"%pg believes seq of %pg to be %llu, but %pg has %llu\n"
"Not using %pg",
sb->bdev, fs->bdev,
fs->bdev, sb->bdev, seq_from_fs,
sb->bdev, seq_from_member,
sb->bdev);
return -BCH_ERR_device_splitbrain;
}
return 0;
}
@ -1770,7 +1815,7 @@ int bch2_dev_online(struct bch_fs *c, const char *path)
dev_idx = sb.sb->dev_idx;
ret = bch2_dev_in_fs(c->disk_sb.sb, sb.sb);
ret = bch2_dev_in_fs(&c->disk_sb, &sb);
bch_err_msg(c, ret, "bringing %s online", path);
if (ret)
goto err;
@ -1911,6 +1956,12 @@ struct bch_dev *bch2_dev_lookup(struct bch_fs *c, const char *name)
/* Filesystem open: */
static inline int sb_cmp(struct bch_sb *l, struct bch_sb *r)
{
return cmp_int(le64_to_cpu(l->seq), le64_to_cpu(r->seq)) ?:
cmp_int(le64_to_cpu(l->write_time), le64_to_cpu(r->write_time));
}
struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
struct bch_opts opts)
{
@ -1948,19 +1999,21 @@ struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
}
darray_for_each(sbs, sb)
if (!best || le64_to_cpu(sb->sb->seq) > le64_to_cpu(best->sb->seq))
if (!best || sb_cmp(sb->sb, best->sb) > 0)
best = sb;
darray_for_each_reverse(sbs, sb) {
if (sb != best && !bch2_dev_exists(best->sb, sb->sb->dev_idx)) {
pr_info("%pg has been removed, skipping", sb->bdev);
ret = bch2_dev_in_fs(best, sb);
if (ret == -BCH_ERR_device_has_been_removed ||
ret == -BCH_ERR_device_splitbrain) {
bch2_free_super(sb);
darray_remove_item(&sbs, sb);
best -= best > sb;
ret = 0;
continue;
}
ret = bch2_dev_in_fs(best->sb, sb->sb);
if (ret)
goto err_print;
}