md/raid5: merge reshape_progress checking inside get_reshape_loc()

JIRA: https://issues.redhat.com/browse/RHEL-83988

commit 1320fe8
Author: Yu Kuai <[email protected]>
Date:   Thu Feb 27 20:04:52 2025 +0800

    md/raid5: merge reshape_progress checking inside get_reshape_loc()

    During code review, it's found that other than raid5_bitmap_sector(),
    reshape_progress is always checked before get_reshape_loc(), while
    raid5_bitmap_sector() should check as well to prevent holding the
    lock 'conf->device_lock'. Hence merge that checking inside
    get_reshape_loc().

    Link: https://lore.kernel.org/linux-raid/[email protected]
    Signed-off-by: Yu Kuai <[email protected]>

Signed-off-by: Nigel Croxon <[email protected]>

Author: ncroxon

drivers/md/raid5.c

@@ -5858,6 +5858,9 @@ static enum reshape_loc get_reshape_loc(struct mddev *mddev,
 		struct r5conf *conf, sector_t logical_sector)
 {
 	sector_t reshape_progress, reshape_safe;
+
+	if (likely(conf->reshape_progress == MaxSector))
+		return LOC_NO_RESHAPE;
 	/*
 	 * Spinlock is needed as reshape_progress may be
 	 * 64bit on a 32bit platform, and so it might be
@@ -5935,22 +5938,19 @@ static enum stripe_result make_stripe_request(struct mddev *mddev,
 	const int rw = bio_data_dir(bi);
 	enum stripe_result ret;
 	struct stripe_head *sh;
+	enum reshape_loc loc;
 	sector_t new_sector;
 	int previous = 0, flags = 0;
 	int seq, dd_idx;
 
 	seq = read_seqcount_begin(&conf->gen_lock);
-
-	if (unlikely(conf->reshape_progress != MaxSector)) {
-		enum reshape_loc loc = get_reshape_loc(mddev, conf,
-						       logical_sector);
-		if (loc == LOC_INSIDE_RESHAPE) {
-			ret = STRIPE_SCHEDULE_AND_RETRY;
-			goto out;
-		}
-		if (loc == LOC_AHEAD_OF_RESHAPE)
-			previous = 1;
+	loc = get_reshape_loc(mddev, conf, logical_sector);
+	if (loc == LOC_INSIDE_RESHAPE) {
+		ret = STRIPE_SCHEDULE_AND_RETRY;
+		goto out;
 	}
+	if (loc == LOC_AHEAD_OF_RESHAPE)
+		previous = 1;
 
 	new_sector = raid5_compute_sector(conf, logical_sector, previous,
 					  &dd_idx, NULL);
@@ -6127,7 +6127,6 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 
 	/* Bail out if conflicts with reshape and REQ_NOWAIT is set */
 	if ((bi->bi_opf & REQ_NOWAIT) &&
-	    (conf->reshape_progress != MaxSector) &&
 	    get_reshape_loc(mddev, conf, logical_sector) == LOC_INSIDE_RESHAPE) {
 		bio_wouldblock_error(bi);
 		if (rw == WRITE)