linux-kernel - Re: [PATCH 5/7] nilfs2: add bmap function to seek a valid key

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Message-Id: <20150326.001932.746965246564732016.konishi.ryusuke@lab.ntt.co.jp>
Date:	Thu, 26 Mar 2015 00:19:32 +0900 (JST)
From:	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-nilfs@...r.kernel.org,
	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
	Dan Carpenter <dan.carpenter@...cle.com>, kbuild@...org
Subject: Re: [PATCH 5/7] nilfs2: add bmap function to seek a valid key

Hi Andrew,

On Thu, 12 Mar 2015 23:38:12 +0900, Ryusuke Konishi wrote:
> Add a new bmap function, nilfs_bmap_seek_key(), which seeks a valid
> entry and returns its key starting from a given key.  This function
> can be used to skip hole blocks efficiently.
> 
> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
> ---
<snip>
> +static int nilfs_btree_seek_key(const struct nilfs_bmap *btree, __u64 start,
> +				__u64 *keyp)
> +{
> +	struct nilfs_btree_path *path;
> +	const int minlevel = NILFS_BTREE_LEVEL_NODE_MIN;
> +	int ret;
> +

> +	if (start > NILFS_BTREE_KEY_MAX)
> +		return -ENOENT;

Could you apply the following amendment ?

I've got a report from Dan Carpenter that this range check causes a
warning:

 fs/nilfs2/btree.c:1611 nilfs_btree_seek_key() warn: impossible condition '(start > (~0)) => (0-u64max > u64max)'

A range check was needed there in a wip patch, but we no longer need
it.

Thanks,
Ryusuke Konishi
--
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index 841d177..059f371 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -1608,9 +1608,6 @@ static int nilfs_btree_seek_key(const struct nilfs_bmap *btree, __u64 start,
 	const int minlevel = NILFS_BTREE_LEVEL_NODE_MIN;
 	int ret;
 
-	if (start > NILFS_BTREE_KEY_MAX)
-		return -ENOENT;
-
 	path = nilfs_btree_alloc_path();
 	if (!path)
 		return -ENOMEM;
-- 
1.8.3.1

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