bcachefs: bch_member->seq

Add new fields for split brain detection:

 - bch_member->seq, which tracks the sequence number of the last superblock
   write that happened to each member device

 - bch_sb->write_time, which tracks the time of the last superblock write,
   to allow detection of when two members have diverged but had the same
   number of superblock writes.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index 2c09b40a15b9bb5a6378d6757ae0ec0d8c3357d6..eb2df422ae5a955e0b03761053be7ab88c69ba80 100644 (file)
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -1303,6 +1303,7 @@ struct bch_member {
        __le64                  errors[BCH_MEMBER_ERROR_NR];
        __le64                  errors_at_reset[BCH_MEMBER_ERROR_NR];
        __le64                  errors_reset_time;
+       __le64                  seq;
 };
 
 #define BCH_MEMBER_V1_BYTES    56
@@ -1729,7 +1730,9 @@ struct bch_sb_field_downgrade {
        x(deleted_inodes,               BCH_VERSION(1,  2),             \
          BIT_ULL(BCH_RECOVERY_PASS_check_inodes))                      \
        x(rebalance_work,               BCH_VERSION(1,  3),             \
-         BIT_ULL(BCH_RECOVERY_PASS_set_fs_needs_rebalance))
+         BIT_ULL(BCH_RECOVERY_PASS_set_fs_needs_rebalance))            \
+       x(member_seq,                   BCH_VERSION(1,  4),             \
+         0)
 
 enum bcachefs_metadata_version {
        bcachefs_metadata_version_min = 9,
@@ -1795,7 +1798,8 @@ struct bch_sb {
        __le32                  time_base_hi;
        __le32                  time_precision;
 
-       __le64                  flags[8];
+       __le64                  flags[7];
+       __le64                  write_time;
        __le64                  features[2];
        __le64                  compat[2];
 

diff --git a/fs/bcachefs/sb-members.c b/fs/bcachefs/sb-members.c
index 7c5db669a46718c342f499504ab321db5d4bffd1..4c19a8096c1dfc4ced3b8ea2db21bedda3cd1352 100644 (file)
--- a/fs/bcachefs/sb-members.c
+++ b/fs/bcachefs/sb-members.c
@@ -235,6 +235,11 @@ static void member_to_text(struct printbuf *out,
                prt_printf(out, "(never)");
        prt_newline(out);
 
+       prt_printf(out, "Last superblock write:");
+       prt_tab(out);
+       prt_u64(out, le64_to_cpu(m.seq));
+       prt_newline(out);
+
        prt_printf(out, "State:");
        prt_tab(out);
        prt_printf(out, "%s",

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index 89d2d2a86eb0b4bef05ecd3dc646843af5f76a1b..aee3c634f4afcd9f4c9e290a5853dff212866e7b 100644 (file)
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -564,6 +564,7 @@ static int __copy_super(struct bch_sb_handle *dst_handle, struct bch_sb *src)
        dst->time_base_lo       = src->time_base_lo;
        dst->time_base_hi       = src->time_base_hi;
        dst->time_precision     = src->time_precision;
+       dst->write_time         = src->write_time;
 
        memcpy(dst->flags,      src->flags,     sizeof(dst->flags));
        memcpy(dst->features,   src->features,  sizeof(dst->features));
@@ -942,6 +943,11 @@ int bch2_write_super(struct bch_fs *c)
 
        le64_add_cpu(&c->disk_sb.sb->seq, 1);
 
+       struct bch_sb_field_members_v2 *mi = bch2_sb_field_get(c->disk_sb.sb, members_v2);
+       for_each_online_member(c, ca)
+               __bch2_members_v2_get_mut(mi, ca->dev_idx)->seq = c->disk_sb.sb->seq;
+       c->disk_sb.sb->write_time = cpu_to_le64(ktime_get_real_seconds());
+
        if (test_bit(BCH_FS_error, &c->flags))
                SET_BCH_SB_HAS_ERRORS(c->disk_sb.sb, 1);
        if (test_bit(BCH_FS_topology_error, &c->flags))
@@ -1304,6 +1310,11 @@ void bch2_sb_to_text(struct printbuf *out, struct bch_sb *sb,
        prt_printf(out, "%llu", le64_to_cpu(sb->seq));
        prt_newline(out);
 
+       prt_printf(out, "Time of last write:");
+       prt_tab(out);
+       bch2_prt_datetime(out, le64_to_cpu(sb->write_time));
+       prt_newline(out);
+
        prt_printf(out, "Superblock size:");
        prt_tab(out);
        prt_printf(out, "%zu", vstruct_bytes(sb));