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@suse.de --- 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); }