Hi,
On Mon, May 23, 2011 at 02:59:06PM +0200, Arne Jansen wrote:
> +static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
> + struct btrfs_device *dev, u64 logical,
> + struct btrfs_multi_bio *multi)
> +{
> + int ret;
> + int looped = 0;
> + struct reada_zone *zone;
> + struct btrfs_block_group_cache *cache = NULL;
> + u64 start;
> + u64 end;
> + int i;
> +
> +again:
> + zone = NULL;
> + spin_lock(&fs_info->reada_lock);
> + ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
> + logical >> PAGE_CACHE_SHIFT, 1);
> + if (ret == 1)
> + kref_get(&zone->refcnt);
> + spin_unlock(&fs_info->reada_lock);
> +
> + if (ret == 1) {
> + if (logical >= zone->start && logical < zone->end)
> + return zone;
> + spin_lock(&fs_info->reada_lock);
> + reada_zone_put(zone);
> + spin_unlock(&fs_info->reada_lock);
> + }
> +
> + if (looped)
> + return NULL;
> +
> + cache = btrfs_lookup_block_group(fs_info, logical);
> + if (!cache)
> + return NULL;
> +
> + start = cache->key.objectid;
> + end = start + cache->key.offset - 1;
> + btrfs_put_block_group(cache);
> +
> + zone = kzalloc(sizeof(*zone), GFP_NOFS);
> + if (!zone)
> + return NULL;
> +
> + zone->start = start;
> + zone->end = end;
> + INIT_LIST_HEAD(&zone->list);
> + spin_lock_init(&zone->lock);
> + zone->locked = 0;
> + kref_init(&zone->refcnt);
> + zone->elems = 0;
> + zone->device = dev; /* our device always sits at index 0 */
> + for (i = 0; i < multi->num_stripes; ++i) {
> + /* bounds have already been checked */
> + zone->devs[i] = multi->stripes[i].dev;
> + }
> + zone->ndevs = multi->num_stripes;
> +
> + spin_lock(&fs_info->reada_lock);
> + ret = radix_tree_insert(&dev->reada_zones,
> + (unsigned long)zone->end >> PAGE_CACHE_SHIFT,
> + zone);
this can sleep inside a spinlock, you initialize the radix tree with
GFP_NOFS, which allows __GFP_WAIT.
Options:
1) use GFP_ATOMIC in radix tree init flags
2) do the radix_tree_preload/radix_tree_preload_end, GFP_NOFS outside of the
locked section is ok but __GFP_WAIT has to be masked out (else radix
tree insert will not use the preloaded node)
3) unmask __GFP_WAIT from radix tree init flags
I'd go for 3, as the atomic context is not required, and is easier
than 2 to implement.
> + spin_unlock(&fs_info->reada_lock);
> +
> + if (ret) {
> + kfree(zone);
> + looped = 1;
> + goto again;
> + }
> +
> + return zone;
> +}
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