1 files changed, 35 insertions, 4 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index d52d4adc440b..5eeb9e0d256e 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -528,7 +528,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                      sector_t offset)
 {
         sector_t alignment;
-        unsigned int top, bottom;
+        unsigned int top, bottom, 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);
@@ -546,6 +546,8 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
         t->max_segment_size = min_not_zero(t->max_segment_size,
                                            b->max_segment_size);
 
+        t->misaligned |= b->misaligned;
+
         alignment = queue_limit_alignment_offset(b, offset);
 
         /* Bottom device has different alignment.  Check that it is
@@ -558,8 +560,10 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                 bottom = max(b->physical_block_size, b->io_min) + alignment;
 
                 /* Verify that top and bottom intervals line up */
-                if (max(top, bottom) & (min(top, bottom) - 1))
+                if (max(top, bottom) & (min(top, bottom) - 1)) {
                         t->misaligned = 1;
+                        ret = -1;
+                }
         }
 
         t->logical_block_size = max(t->logical_block_size,
@@ -578,18 +582,21 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
         if (t->physical_block_size & (t->logical_block_size - 1)) {
                 t->physical_block_size = t->logical_block_size;
                 t->misaligned = 1;
+                ret = -1;
         }
 
         /* Minimum I/O a multiple of the physical block size? */
         if (t->io_min & (t->physical_block_size - 1)) {
                 t->io_min = t->physical_block_size;
                 t->misaligned = 1;
+                ret = -1;
         }
 
         /* Optimal I/O a multiple of the physical block size? */
         if (t->io_opt & (t->physical_block_size - 1)) {
                 t->io_opt = 0;
                 t->misaligned = 1;
+                ret = -1;
         }
 
         /* Find lowest common alignment_offset */
@@ -597,8 +604,10 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                 & (max(t->physical_block_size, t->io_min) - 1);
 
         /* Verify that new alignment_offset is on a logical block boundary */
-        if (t->alignment_offset & (t->logical_block_size - 1))
+        if (t->alignment_offset & (t->logical_block_size - 1)) {
                 t->misaligned = 1;
+                ret = -1;
+        }
 
         /* Discard alignment and granularity */
         if (b->discard_granularity) {
@@ -626,11 +635,33 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
                         (t->discard_granularity - 1);
         }
 
-        return t->misaligned ? -1 : 0;
+        return ret;
 }
 EXPORT_SYMBOL(blk_stack_limits);
 
 /**
+ * bdev_stack_limits - adjust queue limits for stacked drivers
+ * @t:  the stacking driver limits (top device)
+ * @bdev:  the component block_device (bottom)
+ * @start:  first data sector within component device
+ *
+ * Description:
+ *    Merges queue limits for a top device and a block_device.  Returns
+ *    0 if alignment didn't change.  Returns -1 if adding the bottom
+ *    device caused misalignment.
+ */
+int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
+                      sector_t start)
+{
+        struct request_queue *bq = bdev_get_queue(bdev);
+
+        start += get_start_sect(bdev);
+
+        return blk_stack_limits(t, &bq->limits, start << 9);
+}
+EXPORT_SYMBOL(bdev_stack_limits);
+
+/**
  * disk_stack_limits - adjust queue limits for stacked drivers
  * @disk:  MD/DM gendisk (top)
  * @bdev:  the underlying block device (bottom)