From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Fri, 8 Mar 2024 21:10:08 +0000 (-0500)
Subject: bcachefs: Check for writing superblocks with nonsense member seq fields
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c42006458b4239b7eb50f33af523b67c7a55e42e;p=linux.git

bcachefs: Check for writing superblocks with nonsense member seq fields

We're seeing some unmountable filesystems due to split brain detection
going awry; it seems we somehow wrote out superblocks where we updated
the superblock seq without updating any member seq fields.

A given device's superblock should always have the main seq equal to
it's member seq field, so this is easy to check for.

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

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index 38a5073202c57..010daebf987b5 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -470,6 +470,14 @@ static int bch2_sb_validate(struct bch_sb_handle *disk_sb, struct printbuf *out,
 			return ret;
 	}
 
+	if (rw == WRITE &&
+	    bch2_sb_member_get(sb, sb->dev_idx).seq != sb->seq) {
+		prt_printf(out, "Invalid superblock: member seq %llu != sb seq %llu",
+			   le64_to_cpu(bch2_sb_member_get(sb, sb->dev_idx).seq),
+			   le64_to_cpu(sb->seq));
+		return -BCH_ERR_invalid_sb_members_missing;
+	}
+
 	return 0;
 }