[PATCH 5/5] md: clarify the resync ETA comment in status_resync()

The comment above the remaining-time computation was self-contradictory:
it said the original algorithm was being kept but "is not really
necessary", then described that algorithm under an "Original algorithm:"
heading as if it had been replaced. The code still uses it. Rewrite the
comment to simply describe what the code does.

Comment only; no functional change.

Assisted-by: Claude:claude-opus-4-8 [Claude Code]
Signed-off-by: Hiroshi Nishida <[email protected]>
---
 drivers/md/md.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 0cd85cc92ed3..a5c0da0d1133 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8916,17 +8916,11 @@ static int status_resync(struct seq_file *seq, struct mddev *mddev)
 	 * db: blocks written from mark until now
 	 * rt: remaining time
 	 *
-	 * rt is a sector_t, which is always 64bit now. We are keeping
-	 * the original algorithm, but it is not really necessary.
-	 *
-	 * Original algorithm:
-	 *   So we divide before multiply in case it is 32bit and close
-	 *   to the limit.
-	 *   We scale the divisor (db) by 32 to avoid losing precision
-	 *   near the end of resync when the number of remaining sectors
-	 *   is close to 'db'.
-	 *   We then divide rt by 32 after multiplying by db to compensate.
-	 *   The '+1' avoids division by zero if db is very small.
+	 * rt is computed as (remaining sectors) * dt / db.  To keep precision
+	 * near the end of resync, when the remaining count is close to db, the
+	 * divisor db is scaled up by 32 before the divide and rt is scaled back
+	 * down by 32 afterwards.  The '+1' avoids division by zero when db is
+	 * very small.
 	 */
 	dt = ((jiffies - mddev->resync_mark) / HZ);
 	if (!dt) dt++;
-- 
2.43.0