Return early if a page is already in the list of dirty pages for
deferred I/O. This can be detected if the page's list head is not
empty. Keep the list head initialized while the page is not enlisted
to make this work reliably.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
drivers/video/fbdev/core/fb_defio.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c
index a591d291b231..3727b1ca87b1 100644
--- a/drivers/video/fbdev/core/fb_defio.c
+++ b/drivers/video/fbdev/core/fb_defio.c
@@ -59,6 +59,7 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf)
printk(KERN_ERR "no mapping available\n");
BUG_ON(!page->mapping);
+ INIT_LIST_HEAD(&page->lru);
page->index = vmf->pgoff;
vmf->page = page;
@@ -122,17 +123,19 @@ static vm_fault_t fb_deferred_io_mkwrite(struct vm_fault *vmf)
*/
lock_page(page);
+ /*
+ * This check is to catch the case where a new process could start
+ * writing to the same page through a new pte. this new access
+ * can cause the mkwrite even when the original ps's pte is marked
+ * writable.
+ */
+ if (!list_empty(&page->lru))
+ goto page_already_added;
+
/* we loop through the pagelist before adding in order
to keep the pagelist sorted */
list_for_each_entry(cur, &fbdefio->pagelist, lru) {
- /* this check is to catch the case where a new
- process could start writing to the same page
- through a new pte. this new access can cause the
- mkwrite even when the original ps's pte is marked
- writable */
- if (unlikely(cur == page))
- goto page_already_added;
- else if (cur->index > page->index)
+ if (cur->index > page->index)
break;
}
@@ -194,7 +197,7 @@ static void fb_deferred_io_work(struct work_struct *work)
/* clear the list */
list_for_each_safe(node, next, &fbdefio->pagelist) {
- list_del(node);
+ list_del_init(node);
}
mutex_unlock(&fbdefio->lock);
}
--
2.34.1
