mm: rename _count, field of the struct page, to _refcount

Many developers already know that field for reference count of the
struct page is _count and atomic type.  They would try to handle it
directly and this could break the purpose of page reference count
tracepoint.  To prevent direct _count modification, this patch rename it
to _refcount and add warning message on the code.  After that, developer
who need to handle reference count will find that field should not be
accessed directly.

[akpm@linux-foundation.org: fix comments, per Vlastimil]
[akpm@linux-foundation.org: Documentation/vm/transhuge.txt too]
[sfr@canb.auug.org.au: sync ethernet driver changes]
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Sunil Goutham <sgoutham@cavium.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Manish Chopra <manish.chopra@qlogic.com>
Cc: Yuval Mintz <yuval.mintz@qlogic.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 14 insertions, 14 deletions

diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index 437b3a822f44..d597e432e195 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -861,7 +861,7 @@ rqbiocnt(struct request *r)
  * discussion.
  *
  * We cannot use get_page in the workaround, because it insists on a
- * positive page count as a precondition.  So we use _count directly.
+ * positive page count as a precondition.  So we use _refcount directly.
  */
 static void
 bio_pageinc(struct bio *bio)
diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index d9d6022c5aca..d2209147dc89 100644
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -1164,7 +1164,7 @@ static void msc_mmap_close(struct vm_area_struct *vma)
 	if (!atomic_dec_and_mutex_lock(&msc->mmap_count, &msc->buf_mutex))
 		return;
 
-	/* drop page _counts */
+	/* drop page _refcounts */
 	for (pg = 0; pg < msc->nr_pages; pg++) {
 		struct page *page = msc_buffer_get_page(msc, pg);
 
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index f3456798c596..bd947704b59c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -433,8 +433,8 @@ static int mlx5e_alloc_rx_fragmented_mpwqe(struct mlx5e_rq *rq,
 	for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
 		if (unlikely(mlx5e_alloc_and_map_page(rq, wi, i)))
 			goto err_unmap;
-		atomic_add(mlx5e_mpwqe_strides_per_page(rq),
-			   &wi->umr.dma_info[i].page->_count);
+		page_ref_add(wi->umr.dma_info[i].page,
+			     mlx5e_mpwqe_strides_per_page(rq));
 		wi->skbs_frags[i] = 0;
 	}
 
@@ -452,8 +452,8 @@ err_unmap:
 	while (--i >= 0) {
 		dma_unmap_page(rq->pdev, wi->umr.dma_info[i].addr, PAGE_SIZE,
 			       PCI_DMA_FROMDEVICE);
-		atomic_sub(mlx5e_mpwqe_strides_per_page(rq),
-			   &wi->umr.dma_info[i].page->_count);
+		page_ref_sub(wi->umr.dma_info[i].page,
+			     mlx5e_mpwqe_strides_per_page(rq));
 		put_page(wi->umr.dma_info[i].page);
 	}
 	dma_unmap_single(rq->pdev, wi->umr.mtt_addr, mtt_sz, PCI_DMA_TODEVICE);
@@ -477,8 +477,8 @@ void mlx5e_free_rx_fragmented_mpwqe(struct mlx5e_rq *rq,
 	for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
 		dma_unmap_page(rq->pdev, wi->umr.dma_info[i].addr, PAGE_SIZE,
 			       PCI_DMA_FROMDEVICE);
-		atomic_sub(mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i],
-			   &wi->umr.dma_info[i].page->_count);
+		page_ref_sub(wi->umr.dma_info[i].page,
+			mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i]);
 		put_page(wi->umr.dma_info[i].page);
 	}
 	dma_unmap_single(rq->pdev, wi->umr.mtt_addr, mtt_sz, PCI_DMA_TODEVICE);
@@ -527,8 +527,8 @@ static int mlx5e_alloc_rx_linear_mpwqe(struct mlx5e_rq *rq,
 	 */
 	split_page(wi->dma_info.page, MLX5_MPWRQ_WQE_PAGE_ORDER);
 	for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
-		atomic_add(mlx5e_mpwqe_strides_per_page(rq),
-			   &wi->dma_info.page[i]._count);
+		page_ref_add(&wi->dma_info.page[i],
+			     mlx5e_mpwqe_strides_per_page(rq));
 		wi->skbs_frags[i] = 0;
 	}
 
@@ -551,8 +551,8 @@ void mlx5e_free_rx_linear_mpwqe(struct mlx5e_rq *rq,
 	dma_unmap_page(rq->pdev, wi->dma_info.addr, rq->wqe_sz,
 		       PCI_DMA_FROMDEVICE);
 	for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
-		atomic_sub(mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i],
-			   &wi->dma_info.page[i]._count);
+		page_ref_sub(&wi->dma_info.page[i],
+			mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i]);
 		put_page(&wi->dma_info.page[i]);
 	}
 }
diff --git a/drivers/net/ethernet/qlogic/qede/qede_main.c b/drivers/net/ethernet/qlogic/qede/qede_main.c
index 3aabfc0adefe..73dd525fbf08 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_main.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_main.c
@@ -1036,7 +1036,7 @@ static int qede_fill_frag_skb(struct qede_dev *edev,
 		/* Incr page ref count to reuse on allocation failure
 		 * so that it doesn't get freed while freeing SKB.
 		 */
-		atomic_inc(&current_bd->data->_count);
+		page_ref_inc(current_bd->data);
 		goto out;
 	}
 
@@ -1487,7 +1487,7 @@ static int qede_rx_int(struct qede_fastpath *fp, int budget)
 				 * freeing SKB.
 				 */
 
-				atomic_inc(&sw_rx_data->data->_count);
+				page_ref_inc(sw_rx_data->data);
 				rxq->rx_alloc_errors++;
 				qede_recycle_rx_bd_ring(rxq, edev,
 							fp_cqe->bd_num);