path: root/block
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authorJan Kara <jack@suse.cz>2013-09-11 14:26:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 15:59:36 -0700
commit5e4c0d974139a98741b829b27cf38dc8f9284490 (patch)
treefddd959828300c1de1ade15eeb33606c317b79db /block
parent4b39248365e09fb8268b6fecd1704907ffc3d980 (diff)
lib/radix-tree.c: make radix_tree_node_alloc() work correctly within interrupt
With users of radix_tree_preload() run from interrupt (block/blk-ioc.c is one such possible user), the following race can happen: radix_tree_preload() ... radix_tree_insert() radix_tree_node_alloc() if (rtp->nr) { ret = rtp->nodes[rtp->nr - 1]; <interrupt> ... radix_tree_preload() ... radix_tree_insert() radix_tree_node_alloc() if (rtp->nr) { ret = rtp->nodes[rtp->nr - 1]; And we give out one radix tree node twice. That clearly results in radix tree corruption with different results (usually OOPS) depending on which two users of radix tree race. We fix the problem by making radix_tree_node_alloc() always allocate fresh radix tree nodes when in interrupt. Using preloading when in interrupt doesn't make sense since all the allocations have to be atomic anyway and we cannot steal nodes from process-context users because some users rely on radix_tree_insert() succeeding after radix_tree_preload(). in_interrupt() check is somewhat ugly but we cannot simply key off passed gfp_mask as that is acquired from root_gfp_mask() and thus the same for all preload users. Another part of the fix is to avoid node preallocation in radix_tree_preload() when passed gfp_mask doesn't allow waiting. Again, preallocation in such case doesn't make sense and when preallocation would happen in interrupt we could possibly leak some allocated nodes. However, some users of radix_tree_preload() require following radix_tree_insert() to succeed. To avoid unexpected effects for these users, radix_tree_preload() only warns if passed gfp mask doesn't allow waiting and we provide a new function radix_tree_maybe_preload() for those users which get different gfp mask from different call sites and which are prepared to handle radix_tree_insert() failure. Signed-off-by: Jan Kara <jack@suse.cz> Cc: Jens Axboe <jaxboe@fusionio.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'block')
1 files changed, 1 insertions, 1 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 4464c823cff2..46cd7bd18b34 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -367,7 +367,7 @@ struct io_cq *ioc_create_icq(struct io_context *ioc, struct request_queue *q,
if (!icq)
return NULL;
- if (radix_tree_preload(gfp_mask) < 0) {
+ if (radix_tree_maybe_preload(gfp_mask) < 0) {
kmem_cache_free(et->icq_cache, icq);
return NULL;