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Commit bc891c9a authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
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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: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent a506c13a

drivers/block/drbd/drbd_bitmap.c

+9 −7
Original line number Diff line number Diff line
@@ -388,14 +388,16 @@ 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 drbdsetup /

	 * netlink process.  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 dmsetup. */

	bytes = sizeof(struct page *)*want;

	new_pages = kmalloc(bytes, GFP_KERNEL);

	new_pages = kmalloc(bytes, GFP_NOIO);

	if (!new_pages) {

		new_pages = vmalloc(bytes);

		new_pages = __vmalloc(bytes,

				GFP_NOIO | __GFP_HIGHMEM,

				PAGE_KERNEL);

		if (!new_pages)

			return NULL;

		vmalloced = 1;
@@ -406,7 +408,7 @@ 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);