block: Replace SG_GAPS with new queue limits mask

The SG_GAPS queue flag caused checks for bio vector alignment against
PAGE_SIZE, but the device may have different constraints. This patch
adds a queue limits so a driver with such constraints can set to allow
requests that would have been unnecessarily split. The new gaps check
takes the request_queue as a parameter to simplify the logic around
invoking this function.

This new limit makes the queue flag redundant, so removing it and
all usage. Device-mappers will inherit the correct settings through
blk_stack_limits().

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e427debc7008..a622f270f09e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -250,6 +250,7 @@ struct blk_queue_tag {
 struct queue_limits {
 	unsigned long		bounce_pfn;
 	unsigned long		seg_boundary_mask;
+	unsigned long		virt_boundary_mask;
 
 	unsigned int		max_hw_sectors;
 	unsigned int		chunk_sectors;
@@ -479,7 +480,6 @@ struct request_queue {
 #define QUEUE_FLAG_DEAD        19	/* queue tear-down finished */
 #define QUEUE_FLAG_INIT_DONE   20	/* queue is initialized */
 #define QUEUE_FLAG_NO_SG_MERGE 21	/* don't attempt to merge SG segments*/
-#define QUEUE_FLAG_SG_GAPS     22	/* queue doesn't support SG gaps */
 
 #define QUEUE_FLAG_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
 				 (1 << QUEUE_FLAG_STACKABLE)	|	\
@@ -981,6 +981,7 @@ extern int blk_queue_dma_drain(struct request_queue *q,
 			       void *buf, unsigned int size);
 extern void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn);
 extern void blk_queue_segment_boundary(struct request_queue *, unsigned long);
+extern void blk_queue_virt_boundary(struct request_queue *, unsigned long);
 extern void blk_queue_prep_rq(struct request_queue *, prep_rq_fn *pfn);
 extern void blk_queue_unprep_rq(struct request_queue *, unprep_rq_fn *ufn);
 extern void blk_queue_dma_alignment(struct request_queue *, int);
@@ -1149,6 +1150,11 @@ static inline unsigned long queue_segment_boundary(struct request_queue *q)
 	return q->limits.seg_boundary_mask;
 }
 
+static inline unsigned long queue_virt_boundary(struct request_queue *q)
+{
+	return q->limits.virt_boundary_mask;
+}
+
 static inline unsigned int queue_max_sectors(struct request_queue *q)
 {
 	return q->limits.max_sectors;
@@ -1349,6 +1355,19 @@ static inline void put_dev_sector(Sector p)
 	page_cache_release(p.v);
 }
 
+/*
+ * Check if adding a bio_vec after bprv with offset would create a gap in
+ * the SG list. Most drivers don't care about this, but some do.
+ */
+static inline bool bvec_gap_to_prev(struct request_queue *q,
+				struct bio_vec *bprv, unsigned int offset)
+{
+	if (!queue_virt_boundary(q))
+		return false;
+	return offset ||
+		((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
+}
+
 struct work_struct;
 int kblockd_schedule_work(struct work_struct *work);
 int kblockd_schedule_delayed_work(struct delayed_work *dwork, unsigned long delay);