Revert "block: Remove extra discard_alignment from hd_struct."

It was not a good idea to start dereferencing disk->queue from
the fs sysfs strategy for displaying discard alignment. We ran
into first a NULL pointer deref, and after fixing that we sometimes
see unvalid disk->queue pointer values.

Since discard is the only one of the bunch actually looking into
the queue, just revert the change.

This reverts commit 23ceb5b7719e9276d4fa72a3ecf94dd396755276.

Conflicts:
	fs/partitions/check.c

2 files changed, 4 insertions, 7 deletions

diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index f82e762eeca2..d545e97d99c3 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -255,13 +255,7 @@ ssize_t part_discard_alignment_show(struct device *dev,
                                    struct device_attribute *attr, char *buf)
 {
         struct hd_struct *p = dev_to_part(dev);
-        struct gendisk *disk = dev_to_disk(dev);
-        unsigned int alignment = 0;
-
-        if (disk->queue)
-                alignment = queue_limit_discard_alignment(&disk->queue->limits,
-                                                                p->start_sect);
-        return sprintf(buf, "%u\n", alignment);
+        return sprintf(buf, "%u\n", p->discard_alignment);
 }
 
 ssize_t part_stat_show(struct device *dev,
@@ -455,6 +449,8 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
         p->start_sect = start;
         p->alignment_offset =
                 queue_limit_alignment_offset(&disk->queue->limits, start);
+        p->discard_alignment =
+                queue_limit_discard_alignment(&disk->queue->limits, start);
         p->nr_sects = len;
         p->partno = partno;
         p->policy = get_disk_ro(disk);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index b78956b3c2e7..300d7582006e 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -100,6 +100,7 @@ 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;