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SubjectRe: [PATCH v2] lib: Make radix_tree_node_alloc() work correctly within interrupt
On 07/23/13 15:04, Jan Kara wrote:

Hi,

s/sence/sense/ please.


>
> diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> index e796429..7811ed3 100644
> --- a/lib/radix-tree.c
> +++ b/lib/radix-tree.c
> @@ -32,6 +32,7 @@
> #include <linux/string.h>
> #include <linux/bitops.h>
> #include <linux/rcupdate.h>
> +#include <linux/hardirq.h> /* in_interrupt() */
>
>
> #ifdef __KERNEL__
> @@ -207,7 +208,12 @@ radix_tree_node_alloc(struct radix_tree_root *root)
> struct radix_tree_node *ret = NULL;
> gfp_t gfp_mask = root_gfp_mask(root);
>
> - if (!(gfp_mask & __GFP_WAIT)) {
> + /*
> + * Preload code isn't irq safe and it doesn't make sence to use

sense

> + * preloading in the interrupt anyway as all the allocations have to
> + * be atomic. So just do normal allocation when in interrupt.
> + */
> + if (!(gfp_mask & __GFP_WAIT) && !in_interrupt()) {
> struct radix_tree_preload *rtp;
>
> /*
> @@ -264,7 +270,7 @@ radix_tree_node_free(struct radix_tree_node *node)
> * To make use of this facility, the radix tree must be initialised without
> * __GFP_WAIT being passed to INIT_RADIX_TREE().
> */
> -int radix_tree_preload(gfp_t gfp_mask)
> +static int __radix_tree_preload(gfp_t gfp_mask)
> {
> struct radix_tree_preload *rtp;
> struct radix_tree_node *node;
> @@ -288,9 +294,40 @@ int radix_tree_preload(gfp_t gfp_mask)
> out:
> return ret;
> }
> +
> +/*
> + * Load up this CPU's radix_tree_node buffer with sufficient objects to
> + * ensure that the addition of a single element in the tree cannot fail. On
> + * success, return zero, with preemption disabled. On error, return -ENOMEM
> + * with preemption not disabled.
> + *
> + * To make use of this facility, the radix tree must be initialised without
> + * __GFP_WAIT being passed to INIT_RADIX_TREE().
> + */
> +int radix_tree_preload(gfp_t gfp_mask)
> +{
> + /* Warn on non-sensical use... */
> + WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT));
> + return __radix_tree_preload(gfp_mask);
> +}
> EXPORT_SYMBOL(radix_tree_preload);
>
> /*
> + * The same as above function, except we don't guarantee preloading happens.
> + * We do it, if we decide it helps. On success, return zero with preemption
> + * disabled. On error, return -ENOMEM with preemption not disabled.
> + */
> +int radix_tree_maybe_preload(gfp_t gfp_mask)
> +{
> + if (gfp_mask & __GFP_WAIT)
> + return __radix_tree_preload(gfp_mask);
> + /* Preloading doesn't help anything with this gfp mask, skip it */
> + preempt_disable();
> + return 0;
> +}
> +EXPORT_SYMBOL(radix_tree_maybe_preload);
> +
> +/*
> * Return the maximum key which can be store into a

stored

> * radix tree with height HEIGHT.
> */

--
~Randy


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