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-rw-r--r--drivers/video/fb_defio.c20
1 files changed, 19 insertions, 1 deletions
diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index 24843fdd5395..59df132cc375 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -74,6 +74,7 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
74{ 74{
75 struct fb_info *info = vma->vm_private_data; 75 struct fb_info *info = vma->vm_private_data;
76 struct fb_deferred_io *fbdefio = info->fbdefio; 76 struct fb_deferred_io *fbdefio = info->fbdefio;
77 struct page *cur;
77 78
78 /* this is a callback we get when userspace first tries to 79 /* this is a callback we get when userspace first tries to
79 write to the page. we schedule a workqueue. that workqueue 80 write to the page. we schedule a workqueue. that workqueue
@@ -83,7 +84,24 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
83 84
84 /* protect against the workqueue changing the page list */ 85 /* protect against the workqueue changing the page list */
85 mutex_lock(&fbdefio->lock); 86 mutex_lock(&fbdefio->lock);
86 list_add(&page->lru, &fbdefio->pagelist); 87
88 /* we loop through the pagelist before adding in order
89 to keep the pagelist sorted */
90 list_for_each_entry(cur, &fbdefio->pagelist, lru) {
91 /* this check is to catch the case where a new
92 process could start writing to the same page
93 through a new pte. this new access can cause the
94 mkwrite even when the original ps's pte is marked
95 writable */
96 if (unlikely(cur == page))
97 goto page_already_added;
98 else if (cur->index > page->index)
99 break;
100 }
101
102 list_add_tail(&page->lru, &cur->lru);
103
104page_already_added:
87 mutex_unlock(&fbdefio->lock); 105 mutex_unlock(&fbdefio->lock);
88 106
89 /* come back after delay to process the deferred IO */ 107 /* come back after delay to process the deferred IO */