[dm-devel] [PATCH] dm: remove useless loop in __split_and_process_bio

[Mikulas Patocka]

Remove useless "while" loop. If the condition ci.sector_count && !error is
true, we go to a branch that ends with "break". If this condition is
false, the "while" loop will not be executed again. So, the loop can't be
executed more than once.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

---
 drivers/md/dm.c |   57 ++++++++++++++++++++++++++------------------------------
 1 file changed, 27 insertions(+), 30 deletions(-)

Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c	2021-02-23 17:18:54.000000000 +0100
+++ linux-2.6/drivers/md/dm.c	2021-02-26 19:10:31.000000000 +0100
@@ -1584,38 +1584,35 @@ static blk_qc_t __split_and_process_bio(
 	} else {
 		ci.bio = bio;
 		ci.sector_count = bio_sectors(bio);
-		while (ci.sector_count && !error) {
-			error = __split_and_process_non_flush(&ci);
-			if (ci.sector_count && !error) {
-				/*
-				 * Remainder must be passed to submit_bio_noacct()
-				 * so that it gets handled *after* bios already submitted
-				 * have been completely processed.
-				 * We take a clone of the original to store in
-				 * ci.io->orig_bio to be used by end_io_acct() and
-				 * for dec_pending to use for completion handling.
-				 */
-				struct bio *b = bio_split(bio, bio_sectors(bio) - ci.sector_count,
-							  GFP_NOIO, &md->queue->bio_split);
-				ci.io->orig_bio = b;
+		error = __split_and_process_non_flush(&ci);
+		if (ci.sector_count && !error) {
+			/*
+			 * Remainder must be passed to submit_bio_noacct()
+			 * so that it gets handled *after* bios already submitted
+			 * have been completely processed.
+			 * We take a clone of the original to store in
+			 * ci.io->orig_bio to be used by end_io_acct() and
+			 * for dec_pending to use for completion handling.
+			 */
+			struct bio *b = bio_split(bio, bio_sectors(bio) - ci.sector_count,
+						  GFP_NOIO, &md->queue->bio_split);
+			ci.io->orig_bio = b;
 
-				/*
-				 * Adjust IO stats for each split, otherwise upon queue
-				 * reentry there will be redundant IO accounting.
-				 * NOTE: this is a stop-gap fix, a proper fix involves
-				 * significant refactoring of DM core's bio splitting
-				 * (by eliminating DM's splitting and just using bio_split)
-				 */
-				part_stat_lock();
-				__dm_part_stat_sub(dm_disk(md)->part0,
-						   sectors[op_stat_group(bio_op(bio))], ci.sector_count);
-				part_stat_unlock();
+			/*
+			 * Adjust IO stats for each split, otherwise upon queue
+			 * reentry there will be redundant IO accounting.
+			 * NOTE: this is a stop-gap fix, a proper fix involves
+			 * significant refactoring of DM core's bio splitting
+			 * (by eliminating DM's splitting and just using bio_split)
+			 */
+			part_stat_lock();
+			__dm_part_stat_sub(dm_disk(md)->part0,
+					   sectors[op_stat_group(bio_op(bio))], ci.sector_count);
+			part_stat_unlock();
 
-				bio_chain(b, bio);
-				trace_block_split(b, bio->bi_iter.bi_sector);
-				ret = submit_bio_noacct(bio);
-				break;
-			}
+			bio_chain(b, bio);
+			trace_block_split(b, bio->bi_iter.bi_sector);
+			ret = submit_bio_noacct(bio);
 		}
 	}