[PATCH v2 08/16] block: Limit atomic write IO size according to atomic_write_max_sectors

[John Garry]

Currently an IO size is limited to the request_queue limits max_sectors.
Limit the size for an atomic write to queue limit atomic_write_max_sectors
value.

Signed-off-by: John Garry <john.g.garry at oracle.com>
---
 block/blk-merge.c | 12 +++++++++++-
 block/blk.h       |  3 +++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 0ccc251e22ff..8d4de9253fe9 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -171,7 +171,17 @@ static inline unsigned get_max_io_size(struct bio *bio,
 {
 	unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
 	unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
-	unsigned max_sectors = lim->max_sectors, start, end;
+	unsigned max_sectors, start, end;
+
+	/*
+	 * We ignore lim->max_sectors for atomic writes simply because
+	 * it may less than bio->write_atomic_unit, which we cannot
+	 * tolerate.
+	 */
+	if (bio->bi_opf & REQ_ATOMIC)
+		max_sectors = lim->atomic_write_max_sectors;
+	else
+		max_sectors = lim->max_sectors;
 
 	if (lim->chunk_sectors) {
 		max_sectors = min(max_sectors,
diff --git a/block/blk.h b/block/blk.h
index 94e330e9c853..6f6cd5b1830a 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -178,6 +178,9 @@ static inline unsigned int blk_queue_get_max_sectors(struct request *rq)
 	if (unlikely(op == REQ_OP_WRITE_ZEROES))
 		return q->limits.max_write_zeroes_sectors;
 
+	if (rq->cmd_flags & REQ_ATOMIC)
+		return q->limits.atomic_write_max_sectors;
+
 	return q->limits.max_sectors;
 }
 
-- 
2.35.3