linux-kernel - RE: [f2fs-dev] [PATCH v2] f2fs: fix up f2fs_get_parent issue to retrieve correct parent inode number

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Message-id: <060d01cdd986$e708a180$b519e480$%lee@samsung.com>
Date:	Fri, 14 Dec 2012 08:09:28 +0900
From:	이창만 <cm224.lee@...sung.com>
To:	'Namjae Jeon' <linkinjeon@...il.com>, jaegeuk.kim@...sung.com
Cc:	'Amit Sahrawat' <a.sahrawat@...sung.com>,
	'Namjae Jeon' <namjae.jeon@...sung.com>,
	linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-fsdevel@...r.kernel.org
Subject: RE: [f2fs-dev] [PATCH v2] f2fs: fix up f2fs_get_parent issue to
	retrieve correct parent inode number



> -----Original Message-----
> From: Namjae Jeon [mailto:linkinjeon@...il.com]
> Sent: Thursday, December 13, 2012 11:44 PM
> To: jaegeuk.kim@...sung.com
> Cc: Namjae Jeon; Amit Sahrawat; Namjae Jeon; linux-kernel@...r.kernel.org;
> linux-f2fs-devel@...ts.sourceforge.net; linux-fsdevel@...r.kernel.org
> Subject: [f2fs-dev] [PATCH v2] f2fs: fix up f2fs_get_parent issue to
> retrieve correct parent inode number
> 
> From: Namjae Jeon <namjae.jeon@...sung.com>
> 
> Test Case:
> [NFS Client]
> ls -lR .
> 
> [NFS Server]
> while [ 1 ]
> do
> echo 3 > /proc/sys/vm/drop_caches
> done
> 
> Error on NFS Client: "No such file or directory"
> 
> When cache is dropped at the server, it results in lookup failure at the
> NFS client due to non-connection with the parent. The default path is it
> initiates a lookup by calculating the hash value for the name, even though
> the hash values stored on the disk for "." and ".." is maintained as zero,
> which results in failure from find_in_block due to not matching HASH values.
> Fix up, by using the correct hashing values for these entries.
> 
> Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
> Signed-off-by: Amit Sahrawat <a.sahrawat@...sung.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> ---
>  fs/f2fs/dir.c  |    4 ++--
>  fs/f2fs/hash.c |    4 ++++
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index b4e24f3..a158406 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -540,13 +540,13 @@ int f2fs_make_empty(struct inode *inode, struct inode
> *parent)
> 
>  	de = &dentry_blk->dentry[0];
>  	de->name_len = cpu_to_le16(1);
> -	de->hash_code = 0;
> +	de->hash_code = f2fs_dentry_hash(".", 1);
>  	de->ino = cpu_to_le32(inode->i_ino);
>  	memcpy(dentry_blk->filename[0], ".", 1);
>  	set_de_type(de, inode);
> 
>  	de = &dentry_blk->dentry[1];
> -	de->hash_code = 0;
> +	de->hash_code = f2fs_dentry_hash("..", 2);
>  	de->name_len = cpu_to_le16(2);
>  	de->ino = cpu_to_le32(parent->i_ino);
>  	memcpy(dentry_blk->filename[1], "..", 2);
> diff --git a/fs/f2fs/hash.c b/fs/f2fs/hash.c
> index a60f042..5e48bac 100644
> --- a/fs/f2fs/hash.c
> +++ b/fs/f2fs/hash.c
> @@ -76,6 +76,10 @@ f2fs_hash_t f2fs_dentry_hash(const char *name, int len)
>  	const char *p;
>  	__u32 in[8], buf[4];
> 
> +	if ((len <= 2) && (name[0] == '.') &&
> +		(name[1] == '.' || name[1] == '\0'))
> +		return 0;
> +

How about this?
if (!memcmp(name, ".", len) || !memcmp(name, "..", len))
	return 0;


>  	/* Initialize the default seed for the hash checksum functions */
>  	buf[0] = 0x67452301;
>  	buf[1] = 0xefcdab89;
> --
> 1.7.9.5
> 
> 
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