[PATCH 1/3] md/raid10: restore still_degraded detection in recovery

raid10_sync_request()'s recovery arm passes still_degraded -- "will
the array still be degraded after this recovery completes?" -- to
md_bitmap_start_sync(), whose !degraded branch consumes the chunk's
NEEDED marker, the write-intent record.  That is only safe when the
recovery restores full redundancy; otherwise the record still
describes writes an absent member missed.

Commit fe6a19d40ceb ("md/md-bitmap: merge md_bitmap_start_sync()
into bitmap_operations") turned the detection loop's only assignment
from "still_degraded = 1" into "still_degraded = false" in its
int-to-bool styling pass, so the flag has been constant false ever
since.  raid1 and raid5 were converted to "= true"; only raid10 was
inverted.

The result is silent data loss on a classic-bitmap raid10 that stays
degraded across a recovery.  With mirror pairs {A,B} and {C,D}: lose
D, keep writing, lose B, add a spare.  The rebuild into B's slot
strips NEEDED from every chunk -- including chunks whose only
unsatisfied intent belonged to D -- so a later --re-add of D sees an
empty intent record, completes instantly, and serves stale data.

Restore the pre-conversion assignment.  Only the classic-bitmap
recovery arm is affected: llbitmap ignores the degraded parameter,
and the resync arm passes mddev->degraded directly.

Fixes: fe6a19d40ceb ("md/md-bitmap: merge md_bitmap_start_sync() into bitmap_operations")
Cc: [email protected] # v6.12+
Assisted-by: Claude-Code:claude-opus-4-8
Signed-off-by: Mykola Marzhan <[email protected]>
---
 drivers/md/raid10.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0a3cfdd3f5df..54cddb3a98cd 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3365,7 +3365,7 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 				struct md_rdev *rdev = conf->mirrors[j].rdev;
 
 				if (rdev == NULL || test_bit(Faulty, &rdev->flags)) {
-					still_degraded = false;
+					still_degraded = true;
 					break;
 				}
 			}
-- 
2.43.0