md/raid5: fix IO hang with degraded array with llbitmap

When llbitmap bit state is still unwritten, any new write should force
rcw, as bitmap_ops->blocks_synced() is checked in handle_stripe_dirtying().
However, later the same check is missing in need_this_block(), causing
stripe to deadloop during handling because handle_stripe() will decide
to go to handle_stripe_fill(), meanwhile need_this_block() always return
0 and nothing is handled.

Link: https://lore.kernel.org/linux-raid/20260123182623.3718551-2-yukuai@fnnas.com
Fixes: 5ab829f1971d ("md/md-llbitmap: introduce new lockless bitmap")
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Li Nan <linan122@huawei.com>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 6d408aaaacf37ae0538b9510e062621a16d23ad0..8854e024f3113b59dd38ab7a844ef72df1c03849 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3751,9 +3751,14 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
        struct r5dev *dev = &sh->dev[disk_idx];
        struct r5dev *fdev[2] = { &sh->dev[s->failed_num[0]],
                                  &sh->dev[s->failed_num[1]] };
+       struct mddev *mddev = sh->raid_conf->mddev;
+       bool force_rcw = false;
        int i;
-       bool force_rcw = (sh->raid_conf->rmw_level == PARITY_DISABLE_RMW);
 
+       if (sh->raid_conf->rmw_level == PARITY_DISABLE_RMW ||
+           (mddev->bitmap_ops && mddev->bitmap_ops->blocks_synced &&
+            !mddev->bitmap_ops->blocks_synced(mddev, sh->sector)))
+               force_rcw = true;
 
        if (test_bit(R5_LOCKED, &dev->flags) ||
            test_bit(R5_UPTODATE, &dev->flags))