From 0b143d4382b62db6738196caaefa793e5c0f6690 Mon Sep 17 00:00:00 2001 From: Lars Ellenberg Date: Thu, 20 Sep 2012 14:05:39 +0200 Subject: [PATCH] drbd: fix potential deadlock during bitmap (re-)allocation The former comment arguing that GFP_KERNEL was good enough was wrong: it did not take resize into account at all, and assumed the only path leading here was the normal attach on a still secondary device, so no deadlock would be possible. Both resize on a Primary, or attach on a diskless Primary, could potentially deadlock. drbd_bm_resize() is called while IO to the respective device is suspended, so we must use GFP_NOIO to avoid potential deadlock. Signed-off-by: Philipp Reisner Signed-off-by: Lars Ellenberg Signed-off-by: Jens Axboe --- drivers/block/drbd/drbd_bitmap.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c index d845664..dda4e38 100644 --- a/drivers/block/drbd/drbd_bitmap.c +++ b/drivers/block/drbd/drbd_bitmap.c @@ -373,14 +373,16 @@ static struct page **bm_realloc_pages(struct drbd_bitmap *b, unsigned long want) return old_pages; /* Trying kmalloc first, falling back to vmalloc. - * GFP_KERNEL is ok, as this is done when a lower level disk is - * "attached" to the drbd. Context is receiver thread or cqueue - * thread. As we have no disk yet, we are not in the IO path, - * not even the IO path of the peer. */ + * GFP_NOIO, as this is called while drbd IO is "suspended", + * and during resize or attach on diskless Primary, + * we must not block on IO to ourselves. + * Context is receiver thread or cqueue thread/dmsetup. */ bytes = sizeof(struct page *)*want; - new_pages = kzalloc(bytes, GFP_KERNEL); + new_pages = kzalloc(bytes, GFP_NOIO); if (!new_pages) { - new_pages = vzalloc(bytes); + new_pages = __vmalloc(bytes, + GFP_NOIO | __GFP_HIGHMEM | __GFP_ZERO, + PAGE_KERNEL); if (!new_pages) return NULL; vmalloced = 1; @@ -390,7 +392,7 @@ static struct page **bm_realloc_pages(struct drbd_bitmap *b, unsigned long want) for (i = 0; i < have; i++) new_pages[i] = old_pages[i]; for (; i < want; i++) { - page = alloc_page(GFP_HIGHUSER); + page = alloc_page(GFP_NOIO | __GFP_HIGHMEM); if (!page) { bm_free_pages(new_pages + have, i - have); bm_vk_free(new_pages, vmalloced); -- 2.7.4