block: Expose discard granularity

While SSDs track block usage on a per-sector basis, RAID arrays often
have allocation blocks that are bigger.  Allow the discard granularity
and alignment to be set and teach the topology stacking logic how to
handle them.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 39c601f783a0..1cc02972fbe2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -312,12 +312,15 @@ struct queue_limits {
         unsigned int            io_min;
         unsigned int            io_opt;
         unsigned int            max_discard_sectors;
+        unsigned int            discard_granularity;
+        unsigned int            discard_alignment;
 
         unsigned short          logical_block_size;
         unsigned short          max_hw_segments;
         unsigned short          max_phys_segments;
 
         unsigned char           misaligned;
+        unsigned char           discard_misaligned;
         unsigned char           no_cluster;
 };
 
@@ -1121,6 +1124,21 @@ static inline int bdev_alignment_offset(struct block_device *bdev)
         return q->limits.alignment_offset;
 }
 
+static inline int queue_discard_alignment(struct request_queue *q)
+{
+        if (q->limits.discard_misaligned)
+                return -1;
+
+        return q->limits.discard_alignment;
+}
+
+static inline int queue_sector_discard_alignment(struct request_queue *q,
+                                                 sector_t sector)
+{
+        return ((sector << 9) - q->limits.discard_alignment)
+                & (q->limits.discard_granularity - 1);
+}
+
 static inline int queue_dma_alignment(struct request_queue *q)
 {
         return q ? q->dma_alignment : 511;
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 297df45ffd0a..c6c0c41af35f 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -91,6 +91,7 @@ struct hd_struct {
         sector_t start_sect;
         sector_t nr_sects;
         sector_t alignment_offset;
+        unsigned int discard_alignment;
         struct device __dev;
         struct kobject *holder_dir;
         int policy, partno;