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authorLars Ellenberg <lars.ellenberg@linbit.com>2012-09-26 14:18:51 +0200
committerPhilipp Reisner <philipp.reisner@linbit.com>2012-11-09 14:11:39 +0100
commitbc891c9ae3fb2848922e0f0da22fd7de0d58dc1b (patch)
tree58353dfe6fb1257533959a56346b5d5a0a15ad4f /drivers
parenta506c13a4d1ec5e1f2f9bc0123dacb5d123004d3 (diff)
downloadvexpress-lsk-bc891c9ae3fb2848922e0f0da22fd7de0d58dc1b.tar.gz
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 <philipp.reisner@linbit.com> Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/block/drbd/drbd_bitmap.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 4a076b2553e..e502535d2c4 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -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);