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Subject[PATCH v2] radix-tree: must check __radix_tree_preload() return value
From: Eric Dumazet <>

__radix_tree_preload() only disables preemption if no error is returned.

So we really need to make sure callers always check the return value.

idr_preload() contract is to always disable preemption, so we need
to add a missing preempt_disable() if an error happened.

Similarly, ida_pre_get() only needs to call preempt_enable() in the
case no error happened.

Fixes: 0a835c4f090a ("Reimplement IDR and IDA using the radix tree")
Fixes: 7ad3d4d85c7a ("ida: Move ida_bitmap to a percpu variable")
Signed-off-by: Eric Dumazet <>
Cc: <> [4.11+]
v2: addressed Linus feedback, not adding useless/confusing 'ret' variables.

lib/radix-tree.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 3527eb364964..afb3cb4d44b6 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -463,7 +463,7 @@ radix_tree_node_free(struct radix_tree_node *node)
* To make use of this facility, the radix tree must be initialised without
-static int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
+static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
struct radix_tree_preload *rtp;
struct radix_tree_node *node;
@@ -2104,7 +2104,8 @@ EXPORT_SYMBOL(radix_tree_tagged);
void idr_preload(gfp_t gfp_mask)
- __radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE);
+ if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
+ preempt_disable();

@@ -2118,13 +2119,13 @@ EXPORT_SYMBOL(idr_preload);
int ida_pre_get(struct ida *ida, gfp_t gfp)
- __radix_tree_preload(gfp, IDA_PRELOAD_SIZE);
* The IDA API has no preload_end() equivalent. Instead,
* ida_get_new() can return -EAGAIN, prompting the caller
* to return to the ida_pre_get() step.
- preempt_enable();
+ if (!__radix_tree_preload(gfp, IDA_PRELOAD_SIZE))
+ preempt_enable();

if (!this_cpu_read(ida_bitmap)) {
struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);

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