[PATCH] block: Avoid fragmented discard splits for ATA drives

[PATCH] block: Avoid fragmented discard splits for ATA drives

[Tom Yan]

When 0xffffffff >> 9 are splited by 0xffff * 64, there will be a
remainder of 127. Avoid these small fragments by aligning the split
to 128.

Signed-off-by: Tom Yan <tom.ty89@gmail.com>
---
 block/blk.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/block/blk.h b/block/blk.h
index dfab98465db9..1dc12fc86de8 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -281,8 +281,11 @@ static inline unsigned int bio_allowed_max_sectors(struct request_queue *q)
 static inline unsigned int bio_aligned_discard_max_sectors(
 					struct request_queue *q)
 {
-	return round_down(UINT_MAX, q->limits.discard_granularity) >>
-			SECTOR_SHIFT;
+	unsigned int granularity = q->limits.discard_granularity;
+	/* Avoid fragmented splits for ATA drives */
+	if (128 % granularity == 0)
+		granularity = 128;
+	return round_down(UINT_MAX, granularity) >> SECTOR_SHIFT;
 }
 
 /*
-- 
2.29.2