shmem supports page-relocations during swapin since quite some time. It
was implemented in:
commit bde05d1ccd512696b09db9dd2e5f33ad19152605
Author: Hugh Dickins <hughd@xxxxxxxxxx>
Date: Tue May 29 15:06:38 2012 -0700
shmem: replace page if mapping excludes its zone
The gem-comment about wrongly placed DMA32 pages is no longer valid.
Replace it with a proper comment but keep the BUG_ON() to verify correct
shmem behavior.
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
drivers/gpu/drm/drm_gem.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 9909bef..f7d7119 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -474,21 +474,10 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask)
goto fail;
pages[i] = p;
- /* There is a hypothetical issue w/ drivers that require
- * buffer memory in the low 4GB.. if the pages are un-
- * pinned, and swapped out, they can end up swapped back
- * in above 4GB. If pages are already in memory, then
- * shmem_read_mapping_page_gfp will ignore the gfpmask,
- * even if the already in-memory page disobeys the mask.
- *
- * It is only a theoretical issue today, because none of
- * the devices with this limitation can be populated with
- * enough memory to trigger the issue. But this BUG_ON()
- * is here as a reminder in case the problem with
- * shmem_read_mapping_page_gfp() isn't solved by the time
- * it does become a real issue.
- *
- * See this thread: http://lkml.org/lkml/2011/7/11/238
+ /* Make sure shmem keeps __GFP_DMA32 allocated pages in the
+ * correct region during swapin. Note that this requires
+ * __GFP_DMA32 to be set in mapping_gfp_mask(inode->i_mapping)
+ * so shmem can relocate pages during swapin if required.
*/
BUG_ON((gfpmask & __GFP_DMA32) &&
(page_to_pfn(p) >= 0x00100000UL));
--
1.9.3
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
http://lists.freedesktop.org/mailman/listinfo/dri-devel
