Some storage controllers preserve the request order per hardware queue. Some but not all device mapper drivers preserve the bio order. Introduce the feature flag BLK_FEAT_ORDERED_HWQ to allow block drivers and stacked drivers to indicate that the order of write commands is preserved per hardware queue and hence that serialization of writes per zone is not required if all pending writes are submitted to the same hardware queue. Cc: Damien Le Moal Cc: Christoph Hellwig Signed-off-by: Bart Van Assche --- block/blk-settings.c | 2 ++ include/linux/blkdev.h | 6 ++++++ 2 files changed, 8 insertions(+) diff --git a/block/blk-settings.c b/block/blk-settings.c index 78dfef117623..edc25f2d803c 100644 --- a/block/blk-settings.c +++ b/block/blk-settings.c @@ -802,6 +802,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, t->features &= ~BLK_FEAT_NOWAIT; if (!(b->features & BLK_FEAT_POLL)) t->features &= ~BLK_FEAT_POLL; + if (!(b->features & BLK_FEAT_ORDERED_HWQ)) + t->features &= ~BLK_FEAT_ORDERED_HWQ; t->flags |= (b->flags & BLK_FLAG_MISALIGNED); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 2fff8a80dbd2..b97132252ec2 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -348,6 +348,12 @@ typedef unsigned int __bitwise blk_features_t; #define BLK_FEAT_ATOMIC_WRITES \ ((__force blk_features_t)(1u << 16)) +/* + * The request order is preserved per hardware queue by the block driver and by + * the block device. Set by the block driver. + */ +#define BLK_FEAT_ORDERED_HWQ ((__force blk_features_t)(1u << 17)) + /* * Flags automatically inherited when stacking limits. */