dm-integrity: fix recalculation in bitmap mode

There's a logic quirk in the handling of suspend in the bitmap mode:

This is the sequence of calls if we are reloading a dm-integrity table:
* dm_integrity_ctr reads a superblock with the flag SB_FLAG_DIRTY_BITMAP
  set.
* dm_integrity_postsuspend initializes a journal and clears the flag
  SB_FLAG_DIRTY_BITMAP.
* dm_integrity_resume sees the superblock with SB_FLAG_DIRTY_BITMAP set -
  thus it interprets the journal as if it were a bitmap.

This quirk causes recalculation problem if the user increases the size of
the device in the bitmap mode.

Fix this by reading a fresh copy on the superblock in
dm_integrity_resume. This commit also fixes another logic quirk - the
branch that sets bitmap bits if the device was extended should only be
executed if the flag SB_FLAG_DIRTY_BITMAP is set.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Ondrej Kozina <okozina@redhat.com>
Fixes: 468dfca ("dm integrity: add a bitmap mode")
Cc: stable@vger.kernel.org

Author: Mikulas Patocka

drivers/md/dm-integrity.c

@@ -3788,14 +3788,27 @@ static void dm_integrity_resume(struct dm_target *ti)
 	struct dm_integrity_c *ic = ti->private;
 	__u64 old_provided_data_sectors = le64_to_cpu(ic->sb->provided_data_sectors);
 	int r;
+	__le32 flags;
 
 	DEBUG_print("resume\n");
 
 	ic->wrote_to_journal = false;
 
+	flags = ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING);
+	r = sync_rw_sb(ic, REQ_OP_READ);
+	if (r)
+		dm_integrity_io_error(ic, "reading superblock", r);
+	if ((ic->sb->flags & flags) != flags) {
+		ic->sb->flags |= flags;
+		r = sync_rw_sb(ic, REQ_OP_WRITE | REQ_FUA);
+		if (unlikely(r))
+			dm_integrity_io_error(ic, "writing superblock", r);
+	}
+
 	if (ic->provided_data_sectors != old_provided_data_sectors) {
 		if (ic->provided_data_sectors > old_provided_data_sectors &&
 		    ic->mode == 'B' &&
+		    ic->sb->flags & cpu_to_le32(SB_FLAG_DIRTY_BITMAP) &&
 		    ic->sb->log2_blocks_per_bitmap_bit == ic->log2_blocks_per_bitmap_bit) {
 			rw_journal_sectors(ic, REQ_OP_READ, 0,
 					   ic->n_bitmap_blocks * (BITMAP_BLOCK_SIZE >> SECTOR_SHIFT), NULL);