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drbd: fix potential deadlock during bitmap (re-)allocation

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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 <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2012-09-26 14:18:51 +02:00 committed by Philipp Reisner
parent a506c13a4d
commit bc891c9ae3
1 changed files with 9 additions and 7 deletions
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16
drivers/block/drbd/drbd_bitmap.c
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@ -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);