mm: introduce page reference manipulation functions

The success of CMA allocation largely depends on the success of
migration and key factor of it is page reference count.  Until now, page
reference is manipulated by direct calling atomic functions so we cannot
follow up who and where manipulate it.  Then, it is hard to find actual
reason of CMA allocation failure.  CMA allocation should be guaranteed
to succeed so finding offending place is really important.

In this patch, call sites where page reference is manipulated are
converted to introduced wrapper function.  This is preparation step to
add tracepoint to each page reference manipulation function.  With this
facility, we can easily find reason of CMA allocation failure.  There is
no functional change in this patch.

In addition, this patch also converts reference read sites.  It will
help a second step that renames page._count to something else and
prevents later attempt to direct access to it (Suggested by Andrew).

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

8 files changed, 12 insertions, 13 deletions

diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index d048d2009e89..437b3a822f44 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -875,7 +875,7 @@ bio_pageinc(struct bio *bio)
 		 * compound pages is no longer allowed by the kernel.
 		 */
 		page = compound_head(bv.bv_page);
-		atomic_inc(&page->_count);
+		page_ref_inc(page);
 	}
 }
 
@@ -888,7 +888,7 @@ bio_pagedec(struct bio *bio)
 
 	bio_for_each_segment(bv, bio, iter) {
 		page = compound_head(bv.bv_page);
-		atomic_dec(&page->_count);
+		page_ref_dec(page);
 	}
 }
 
diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index b9ecf197ad11..f21b2c479780 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -2944,7 +2944,7 @@ static bool gfar_add_rx_frag(struct gfar_rx_buff *rxb, u32 lstatus,
 	/* change offset to the other half */
 	rxb->page_offset ^= GFAR_RXB_TRUESIZE;
 
-	atomic_inc(&page->_count);
+	page_ref_inc(page);
 
 	return true;
 }
diff --git a/drivers/net/ethernet/intel/fm10k/fm10k_main.c b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
index b243c3cbe68f..b4547ebed774 100644
--- a/drivers/net/ethernet/intel/fm10k/fm10k_main.c
+++ b/drivers/net/ethernet/intel/fm10k/fm10k_main.c
@@ -243,7 +243,7 @@ static bool fm10k_can_reuse_rx_page(struct fm10k_rx_buffer *rx_buffer,
 	/* Even if we own the page, we are not allowed to use atomic_set()
 	 * This would break get_page_unless_zero() users.
 	 */
-	atomic_inc(&page->_count);
+	page_ref_inc(page);
 
 	return true;
 }
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 31e5f3942839..5b4ad1ad4d5f 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -6630,7 +6630,7 @@ static bool igb_can_reuse_rx_page(struct igb_rx_buffer *rx_buffer,
 	/* Even if we own the page, we are not allowed to use atomic_set()
 	 * This would break get_page_unless_zero() users.
 	 */
-	atomic_inc(&page->_count);
+	page_ref_inc(page);
 
 	return true;
 }
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index c4003a88bbf6..e6035ff6b861 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -1942,7 +1942,7 @@ static bool ixgbe_add_rx_frag(struct ixgbe_ring *rx_ring,
 	/* Even if we own the page, we are not allowed to use atomic_set()
 	 * This would break get_page_unless_zero() users.
 	 */
-	atomic_inc(&page->_count);
+	page_ref_inc(page);
 
 	return true;
 }
diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
index 3558f019b631..0ea14c0a2e74 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
@@ -837,7 +837,7 @@ add_tail_frag:
 	/* Even if we own the page, we are not allowed to use atomic_set()
 	 * This would break get_page_unless_zero() users.
 	 */
-	atomic_inc(&page->_count);
+	page_ref_inc(page);
 
 	return true;
 }
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
index 41440b2b20a3..86bcfe510e4e 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
@@ -82,8 +82,7 @@ static int mlx4_alloc_pages(struct mlx4_en_priv *priv,
 	/* Not doing get_page() for each frag is a big win
 	 * on asymetric workloads. Note we can not use atomic_set().
 	 */
-	atomic_add(page_alloc->page_size / frag_info->frag_stride - 1,
-		   &page->_count);
+	page_ref_add(page, page_alloc->page_size / frag_info->frag_stride - 1);
 	return 0;
 }
 
@@ -127,7 +126,7 @@ out:
 			dma_unmap_page(priv->ddev, page_alloc[i].dma,
 				page_alloc[i].page_size, PCI_DMA_FROMDEVICE);
 			page = page_alloc[i].page;
-			atomic_set(&page->_count, 1);
+			set_page_count(page, 1);
 			put_page(page);
 		}
 	}
@@ -165,7 +164,7 @@ static int mlx4_en_init_allocator(struct mlx4_en_priv *priv,
 
 		en_dbg(DRV, priv, "  frag %d allocator: - size:%d frags:%d\n",
 		       i, ring->page_alloc[i].page_size,
-		       atomic_read(&ring->page_alloc[i].page->_count));
+		       page_ref_count(ring->page_alloc[i].page));
 	}
 	return 0;
 
@@ -177,7 +176,7 @@ out:
 		dma_unmap_page(priv->ddev, page_alloc->dma,
 			       page_alloc->page_size, PCI_DMA_FROMDEVICE);
 		page = page_alloc->page;
-		atomic_set(&page->_count, 1);
+		set_page_count(page, 1);
 		put_page(page);
 		page_alloc->page = NULL;
 	}
diff --git a/drivers/net/ethernet/sun/niu.c b/drivers/net/ethernet/sun/niu.c
index ab6051a43134..9cc45649f477 100644
--- a/drivers/net/ethernet/sun/niu.c
+++ b/drivers/net/ethernet/sun/niu.c
@@ -3341,7 +3341,7 @@ static int niu_rbr_add_page(struct niu *np, struct rx_ring_info *rp,
 
 	niu_hash_page(rp, page, addr);
 	if (rp->rbr_blocks_per_page > 1)
-		atomic_add(rp->rbr_blocks_per_page - 1, &page->_count);
+		page_ref_add(page, rp->rbr_blocks_per_page - 1);
 
 	for (i = 0; i < rp->rbr_blocks_per_page; i++) {
 		__le32 *rbr = &rp->rbr[start_index + i];