5.15-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Zimmermann tzimmermann@suse.de
[ Upstream commit 105a940416fc622406653b6fe54732897642dfbc ]
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.
v2: * update comment and fix spelling (Sam)
Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Acked-by: Sam Ravnborg sam@ravnborg.org Link: https://patchwork.freedesktop.org/patch/msgid/20220211094640.21632-2-tzimmer... Stable-dep-of: 33cd6ea9c067 ("fbdev: flush deferred IO before closing") Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/core/fb_defio.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-)
diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index 0708e214c5a3..95264a621221 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; @@ -118,17 +119,24 @@ 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 a call to .page_mkwrite even if the original process' + * PTE is marked writable. + * + * TODO: The lru field is owned by the page cache; hence the name. + * We dequeue in fb_deferred_io_work() after flushing the + * page's content into video memory. Instead of lru, fbdefio + * should have it's own field. + */ + 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; }
@@ -190,7 +198,7 @@ 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); }