linux-ext4 - Re: [RFC v4+ hot_track 03/19] vfs: add I/O frequency update function

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Date:	Wed, 7 Nov 2012 15:03:54 +0800
From:	Zhi Yong Wu <zwu.kernel@...il.com>
To:	dave@...os.cz, zwu.kernel@...il.com, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxram@...ux.vnet.ibm.com,
	viro@...iv.linux.org.uk, david@...morbit.com, tytso@....edu,
	cmm@...ibm.com, wuzhy@...ux.vnet.ibm.com, wenqing.lz@...bao.com
Subject: Re: [RFC v4+ hot_track 03/19] vfs: add I/O frequency update function

On Wed, Nov 7, 2012 at 6:37 AM, David Sterba <dave@...os.cz> wrote:
> On Mon, Oct 29, 2012 at 12:30:45PM +0800, zwu.kernel@...il.com wrote:
>> --- a/fs/hot_tracking.c
>> +++ b/fs/hot_tracking.c
>> +struct hot_inode_item
>> +*hot_inode_item_find(struct hot_info *root, u64 ino)
>> +{
>> +     struct hot_inode_item *he;
>> +     int ret;
>> +
>> +again:
>> +     spin_lock(&root->lock);
>> +     he = radix_tree_lookup(&root->hot_inode_tree, ino);
>> +     if (he) {
>> +             kref_get(&he->hot_inode.refs);
>> +             spin_unlock(&root->lock);
>> +             return he;
>> +     }
>> +     spin_unlock(&root->lock);
>> +
>> +     he = kmem_cache_zalloc(hot_inode_item_cachep,
>> +                             GFP_KERNEL | GFP_NOFS);
>> +     if (!he)
>> +             return ERR_PTR(-ENOMEM);
>> +
>> +     hot_inode_item_init(he, ino, &root->hot_inode_tree);
>> +
>> +     ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
>> +     if (ret) {
>> +             kmem_cache_free(hot_inode_item_cachep, he);
>
>                 radix_tree_preload_end()
>
>> +             return ERR_PTR(ret);
>> +     }
>> +
>> +     spin_lock(&root->lock);
>> +     ret = radix_tree_insert(&root->hot_inode_tree, ino, he);
>> +     if (ret == -EEXIST) {
>> +             kmem_cache_free(hot_inode_item_cachep, he);
>> +             spin_unlock(&root->lock);
>> +             radix_tree_preload_end();
>> +             goto again;
>> +     }
>> +     spin_unlock(&root->lock);
>> +     radix_tree_preload_end();
>> +
>> +     kref_get(&he->hot_inode.refs);
>> +     return he;
>> +}
>> +EXPORT_SYMBOL_GPL(hot_inode_item_find);
>> +
>> +static struct hot_range_item
>> +*hot_range_item_find(struct hot_inode_item *he,
>> +                     u32 start)
>> +{
>> +     struct hot_range_item *hr;
>> +     int ret;
>> +
>> +again:
>> +     spin_lock(&he->lock);
>> +     hr = radix_tree_lookup(&he->hot_range_tree, start);
>> +     if (hr) {
>> +             kref_get(&hr->hot_range.refs);
>> +             spin_unlock(&he->lock);
>> +             return hr;
>> +     }
>> +     spin_unlock(&he->lock);
>> +
>> +     hr = kmem_cache_zalloc(hot_range_item_cachep,
>> +                             GFP_KERNEL | GFP_NOFS);
>> +     if (!hr)
>> +             return ERR_PTR(-ENOMEM);
>> +
>> +     hot_range_item_init(hr, start, he);
>> +
>> +     ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
>> +     if (ret) {
>> +             kmem_cache_free(hot_range_item_cachep, hr);
>
>                 radix_tree_preload_end()
I checked some kernel existing cases about the usage of
radix_tree_preload(), it seems that when radix_tree_preload() fail,
its error handling doesn't need call radix_tree_preload_end() any
more.
>
>> +             return ERR_PTR(ret);
>> +     }
>> +
>> +     spin_lock(&he->lock);
>> +     ret = radix_tree_insert(&he->hot_range_tree, start, hr);
>> +     if (ret == -EEXIST) {
>> +             kmem_cache_free(hot_range_item_cachep, hr);
>> +             spin_unlock(&he->lock);
>> +             radix_tree_preload_end();
ditto.
>> +             goto again;
>> +     }
>> +     spin_unlock(&he->lock);
>> +     radix_tree_preload_end();
>> +
>> +     kref_get(&hr->hot_range.refs);
>> +     return hr;
>> +}
>
> david



-- 
Regards,

Zhi Yong Wu
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