[PATCH v2] drm/gem: Mark pinned pages as unevictable

[Kuo-Hsin Yang]

The gem drivers use shmemfs to allocate backing storage for gem objects.
On Samsung Chromebook Plus, the drm/rockchip driver may call
rockchip_gem_get_pages -> drm_gem_get_pages -> shmem_read_mapping_page
to pin a lot of pages, breaking the page reclaim mechanism and causing
oom-killer invocation.

E.g. when the size of a zone is 3.9 GiB, the inactive_ratio is 5. If
active_anon / inactive_anon < 5 and all pages in the inactive_anon lru
are pinned, page reclaim would keep scanning inactive_anon lru without
reclaiming memory. It breaks page reclaim when the rockchip driver only
pins about 1/6 of the anon lru pages.

Mark these pinned pages as unevictable to avoid the premature oom-killer
invocation. See also similar patch on i915 driver [1].

[1]: https://patchwork.freedesktop.org/patch/msgid/20181106132324.17390-1-chris@chris-wilson.co.uk

Signed-off-by: Kuo-Hsin Yang <vovoy at chromium.org>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/drm_gem.c | 36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 8b55ece97967f..2896ff60552f5 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -37,6 +37,7 @@
 #include <linux/shmem_fs.h>
 #include <linux/dma-buf.h>
 #include <linux/mem_encrypt.h>
+#include <linux/pagevec.h>
 #include <drm/drmP.h>
 #include <drm/drm_vma_manager.h>
 #include <drm/drm_gem.h>
@@ -526,6 +527,17 @@ int drm_gem_create_mmap_offset(struct drm_gem_object *obj)
 }
 EXPORT_SYMBOL(drm_gem_create_mmap_offset);
 
+/*
+ * Move pages to appropriate lru and release the pagevec, decrementing the
+ * ref count of those pages.
+ */
+static void drm_gem_check_release_pagevec(struct pagevec *pvec)
+{
+	check_move_unevictable_pages(pvec);
+	__pagevec_release(pvec);
+	cond_resched();
+}
+
 /**
  * drm_gem_get_pages - helper to allocate backing pages for a GEM object
  * from shmem
@@ -551,6 +563,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
 {
 	struct address_space *mapping;
 	struct page *p, **pages;
+	struct pagevec pvec;
 	int i, npages;
 
 	/* This is the shared memory object that backs the GEM resource */
@@ -568,6 +581,8 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
 	if (pages == NULL)
 		return ERR_PTR(-ENOMEM);
 
+	mapping_set_unevictable(mapping);
+
 	for (i = 0; i < npages; i++) {
 		p = shmem_read_mapping_page(mapping, i);
 		if (IS_ERR(p))
@@ -586,8 +601,14 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
 	return pages;
 
 fail:
-	while (i--)
-		put_page(pages[i]);
+	mapping_clear_unevictable(mapping);
+	pagevec_init(&pvec);
+	while (i--) {
+		if (!pagevec_add(&pvec, pages[i]))
+			drm_gem_check_release_pagevec(&pvec);
+	}
+	if (pagevec_count(&pvec))
+		drm_gem_check_release_pagevec(&pvec);
 
 	kvfree(pages);
 	return ERR_CAST(p);
@@ -605,6 +626,11 @@ void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
 		bool dirty, bool accessed)
 {
 	int i, npages;
+	struct address_space *mapping;
+	struct pagevec pvec;
+
+	mapping = file_inode(obj->filp)->i_mapping;
+	mapping_clear_unevictable(mapping);
 
 	/* We already BUG_ON() for non-page-aligned sizes in
 	 * drm_gem_object_init(), so we should never hit this unless
@@ -614,6 +640,7 @@ void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
 
 	npages = obj->size >> PAGE_SHIFT;
 
+	pagevec_init(&pvec);
 	for (i = 0; i < npages; i++) {
 		if (dirty)
 			set_page_dirty(pages[i]);
@@ -622,8 +649,11 @@ void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
 			mark_page_accessed(pages[i]);
 
 		/* Undo the reference we took when populating the table */
-		put_page(pages[i]);
+		if (!pagevec_add(&pvec, pages[i]))
+			drm_gem_check_release_pagevec(&pvec);
 	}
+	if (pagevec_count(&pvec))
+		drm_gem_check_release_pagevec(&pvec);
 
 	kvfree(pages);
 }
-- 
2.20.0.405.gbc1bbc6f85-goog