drbd: replace kmap() with kmap_local_page() in receiver path

Use kmap_local_page() instead of kmap() to avoid
CPU contention.

kmap() uses a global set of mapping slots that can cause contention
between multiple CPUs, while kmap_local_page() uses per-CPU slots
eliminating this contention. It also ensures non-sleeping operation
and provides better cache locality.

Convert kmap() to kmap_local_page() as it aligns with ongoing
kernel efforts to modernize kmap() usage for better multi-core
scalability.

Signed-off-by: Shi Hao <i.shihao.999@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index caaf2781136d0930aa260a576f40578275f0dcb0..14821420ea50ca6b1f6c231583cfa73cc08f2411 100644 (file)
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1736,13 +1736,13 @@ read_in_block(struct drbd_peer_device *peer_device, u64 id, sector_t sector,
        page = peer_req->pages;
        page_chain_for_each(page) {
                unsigned len = min_t(int, ds, PAGE_SIZE);
-               data = kmap(page);
+               data = kmap_local_page(page);
                err = drbd_recv_all_warn(peer_device->connection, data, len);
                if (drbd_insert_fault(device, DRBD_FAULT_RECEIVE)) {
                        drbd_err(device, "Fault injection: Corrupting data on receive\n");
                        data[0] = data[0] ^ (unsigned long)-1;
                }
-               kunmap(page);
+               kunmap_local(data);
                if (err) {
                        drbd_free_peer_req(device, peer_req);
                        return NULL;
@@ -1777,7 +1777,7 @@ static int drbd_drain_block(struct drbd_peer_device *peer_device, int data_size)
 
        page = drbd_alloc_pages(peer_device, 1, 1);
 
-       data = kmap(page);
+       data = kmap_local_page(page);
        while (data_size) {
                unsigned int len = min_t(int, data_size, PAGE_SIZE);
 
@@ -1786,7 +1786,7 @@ static int drbd_drain_block(struct drbd_peer_device *peer_device, int data_size)
                        break;
                data_size -= len;
        }
-       kunmap(page);
+       kunmap_local(data);
        drbd_free_pages(peer_device->device, page);
        return err;
 }