3 files changed, 70 insertions, 10 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 66d4aa8799b7..7f986cafacd5 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -96,7 +96,10 @@ void blk_set_default_limits(struct queue_limits *lim)
         lim->max_segment_size = MAX_SEGMENT_SIZE;
         lim->max_sectors = BLK_DEF_MAX_SECTORS;
         lim->max_hw_sectors = INT_MAX;
-        lim->max_discard_sectors = SAFE_MAX_SECTORS;
+        lim->max_discard_sectors = 0;
+        lim->discard_granularity = 0;
+        lim->discard_alignment = 0;
+        lim->discard_misaligned = 0;
         lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
         lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
         lim->alignment_offset = 0;
@@ -488,6 +491,16 @@ void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
 }
 EXPORT_SYMBOL(blk_queue_stack_limits);
 
+static unsigned int lcm(unsigned int a, unsigned int b)
+{
+        if (a && b)
+                return (a * b) / gcd(a, b);
+        else if (b)
+                return b;
+
+        return a;
+}
+
 /**
  * blk_stack_limits - adjust queue_limits for stacked devices
  * @t:  the stacking driver limits (top)
@@ -502,6 +515,10 @@ EXPORT_SYMBOL(blk_queue_stack_limits);
 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                      sector_t offset)
 {
+        int ret;
+
+        ret = 0;
+
         t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
         t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
         t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
@@ -531,7 +548,13 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
         if (offset &&
             (offset & (b->physical_block_size - 1)) != b->alignment_offset) {
                 t->misaligned = 1;
-                return -1;
+                ret = -1;
+        }
+
+        if (offset &&
+            (offset & (b->discard_granularity - 1)) != b->discard_alignment) {
+                t->discard_misaligned = 1;
+                ret = -1;
         }
 
         /* If top has no alignment offset, inherit from bottom */
@@ -539,23 +562,26 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                 t->alignment_offset =
                         b->alignment_offset & (b->physical_block_size - 1);
 
+        if (!t->discard_alignment)
+                t->discard_alignment =
+                        b->discard_alignment & (b->discard_granularity - 1);
+
         /* Top device aligned on logical block boundary? */
         if (t->alignment_offset & (t->logical_block_size - 1)) {
                 t->misaligned = 1;
-                return -1;
+                ret = -1;
         }
 
-        /* Find lcm() of optimal I/O size */
-        if (t->io_opt && b->io_opt)
-                t->io_opt = (t->io_opt * b->io_opt) / gcd(t->io_opt, b->io_opt);
-        else if (b->io_opt)
-                t->io_opt = b->io_opt;
+        /* Find lcm() of optimal I/O size and granularity */
+        t->io_opt = lcm(t->io_opt, b->io_opt);
+        t->discard_granularity = lcm(t->discard_granularity,
+                                     b->discard_granularity);
 
         /* Verify that optimal I/O size is a multiple of io_min */
         if (t->io_min && t->io_opt % t->io_min)
-                return -1;
+                ret = -1;
 
-        return 0;
+        return ret;
 }
 EXPORT_SYMBOL(blk_stack_limits);
 
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 8a6d81afb284..3147145edc15 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -126,6 +126,16 @@ static ssize_t queue_io_opt_show(struct request_queue *q, char *page)
         return queue_var_show(queue_io_opt(q), page);
 }
 
+static ssize_t queue_discard_granularity_show(struct request_queue *q, char *page)
+{
+        return queue_var_show(q->limits.discard_granularity, page);
+}
+
+static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
+{
+        return queue_var_show(q->limits.max_discard_sectors << 9, page);
+}
+
 static ssize_t
 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
 {
@@ -293,6 +303,16 @@ static struct queue_sysfs_entry queue_io_opt_entry = {
         .show = queue_io_opt_show,
 };
 
+static struct queue_sysfs_entry queue_discard_granularity_entry = {
+        .attr = {.name = "discard_granularity", .mode = S_IRUGO },
+        .show = queue_discard_granularity_show,
+};
+
+static struct queue_sysfs_entry queue_discard_max_entry = {
+        .attr = {.name = "discard_max_bytes", .mode = S_IRUGO },
+        .show = queue_discard_max_show,
+};
+
 static struct queue_sysfs_entry queue_nonrot_entry = {
         .attr = {.name = "rotational", .mode = S_IRUGO | S_IWUSR },
         .show = queue_nonrot_show,
@@ -328,6 +348,8 @@ static struct attribute *default_attrs[] = {
         &queue_physical_block_size_entry.attr,
         &queue_io_min_entry.attr,
         &queue_io_opt_entry.attr,
+        &queue_discard_granularity_entry.attr,
+        &queue_discard_max_entry.attr,
         &queue_nonrot_entry.attr,
         &queue_nomerges_entry.attr,
         &queue_rq_affinity_entry.attr,
diff --git a/block/genhd.c b/block/genhd.c
index 517e4332cb37..b11a4ad7d571 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -861,12 +861,23 @@ static ssize_t disk_alignment_offset_show(struct device *dev,
         return sprintf(buf, "%d\n", queue_alignment_offset(disk->queue));
 }
 
+static ssize_t disk_discard_alignment_show(struct device *dev,
+                                           struct device_attribute *attr,
+                                           char *buf)
+{
+        struct gendisk *disk = dev_to_disk(dev);
+
+        return sprintf(buf, "%u\n", queue_discard_alignment(disk->queue));
+}
+
 static DEVICE_ATTR(range, S_IRUGO, disk_range_show, NULL);
 static DEVICE_ATTR(ext_range, S_IRUGO, disk_ext_range_show, NULL);
 static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);
 static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL);
 static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);
 static DEVICE_ATTR(alignment_offset, S_IRUGO, disk_alignment_offset_show, NULL);
+static DEVICE_ATTR(discard_alignment, S_IRUGO, disk_discard_alignment_show,
+                   NULL);
 static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL);
 static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);
 static DEVICE_ATTR(inflight, S_IRUGO, part_inflight_show, NULL);
@@ -887,6 +898,7 @@ static struct attribute *disk_attrs[] = {
         &dev_attr_ro.attr,
         &dev_attr_size.attr,
         &dev_attr_alignment_offset.attr,
+        &dev_attr_discard_alignment.attr,
         &dev_attr_capability.attr,
         &dev_attr_stat.attr,
         &dev_attr_inflight.attr,