[PATCH 2/4] block: only define 'nr_sects_seq' in hd_part for 32bit SMP

Ming Lei
2020-05-07T08:53:09Z

The seqcount of 'nr_sects_seq' is only needed in case of 32bit SMP,
so define it just for 32bit SMP.

Cc: Yufen Yu <yuyufen@huawei.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hou Tao <houtao1@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/genhd.c | 2 +-
block/partitions/core.c | 2 +-
include/linux/genhd.h | 9 +++++++++
3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 8b33f0e54356..c0288b89a7ad 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1724,7 +1724,7 @@ struct gendisk *__alloc_disk_node(int minors, int node_id)
* TODO: Ideally set_capacity() and get_capacity() should be
* converted to make use of bd_mutex and sequence counters.
*/
- seqcount_init(&disk->part0.nr_sects_seq);
+ hd_sects_seq_init(&disk->part0);
if (hd_ref_init(&disk->part0)) {
hd_free_part(&disk->part0);
kfree(disk);
diff --git a/block/partitions/core.c b/block/partitions/core.c
index b6cbc9b98426..efccb1be4c5c 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -391,7 +391,7 @@ static struct hd_struct *add_partition(struct gendisk *disk, int partno,
goto out_free;
}

- seqcount_init(&p->nr_sects_seq);
+ hd_sects_seq_init(p);
pdev = part_to_dev(p);

p->start_sect = start;
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index c28d1d9bfa72..2732120751e8 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -68,7 +68,9 @@ struct hd_struct {
* can be non-atomic on 32bit machines with 64bit sector_t.
*/
sector_t nr_sects;
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
seqcount_t nr_sects_seq;
+#endif
sector_t alignment_offset;
unsigned int discard_alignment;
struct device __dev;
@@ -275,6 +277,13 @@ static inline void disk_put_part(struct hd_struct *part)
put_device(part_to_dev(part));
}

+static inline void hd_sects_seq_init(struct hd_struct *p)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+ seqcount_init(&p->nr_sects_seq);
+#endif
+}
+
/*
* Smarter partition iterator without context limits.
*/
--
2.25.2