linux-kernel - Re: [PATCH 3/5] 9p: Simplify the xattr handlers

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Date:	Mon, 21 Sep 2015 13:00:57 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Andreas Gruenbacher <andreas.gruenbacher@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Artem Bityutskiy <dedekind1@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-mtd@...ts.infradead.org, Richard Weinberger <richard@....at>,
	Eric Van Hensbergen <ericvh@...il.com>,
	Ron Minnich <rminnich@...dia.gov>,
	Latchesar Ionkov <lucho@...kov.net>,
	v9fs-developer@...ts.sourceforge.net
Subject: Re: [PATCH 3/5] 9p: Simplify the xattr handlers

Andreas Gruenbacher <andreas.gruenbacher@...il.com> writes:

> The generic_{get,set,remove}xattr inode operations use the xattr name prefix to
> decide which of the defined xattr handlers to call, then call the appropriate
> handler's get or set operation.  The name suffix is passed to the get or set
> operations, the prefix is still "there" in the name before the suffix though.
> There is no need to recompose the name in a temporary buffer.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
> ---
>  fs/9p/xattr_security.c | 34 ++++------------------------------
>  fs/9p/xattr_trusted.c  | 34 ++++------------------------------
>  fs/9p/xattr_user.c     | 34 ++++------------------------------
>  3 files changed, 12 insertions(+), 90 deletions(-)
>
> diff --git a/fs/9p/xattr_security.c b/fs/9p/xattr_security.c
> index cb247a1..2c9b394 100644
> --- a/fs/9p/xattr_security.c
> +++ b/fs/9p/xattr_security.c
> @@ -22,10 +22,7 @@
>  static int v9fs_xattr_security_get(struct dentry *dentry, const char *name,
>  			void *buffer, size_t size, int type)
>  {
> -	int retval;
> -	char *full_name;
> -	size_t name_len;
> -	size_t prefix_len = XATTR_SECURITY_PREFIX_LEN;
> +	const char *full_name = name - XATTR_SECURITY_PREFIX_LEN;
>  
>  	if (name == NULL)
>  		return -EINVAL;
> @@ -33,26 +30,13 @@ static int v9fs_xattr_security_get(struct dentry *dentry, const char *name,
>  	if (strcmp(name, "") == 0)
>  		return -EINVAL;
>  
> -	name_len = strlen(name);
> -	full_name = kmalloc(prefix_len + name_len + 1 , GFP_KERNEL);
> -	if (!full_name)
> -		return -ENOMEM;
> -	memcpy(full_name, XATTR_SECURITY_PREFIX, prefix_len);
> -	memcpy(full_name+prefix_len, name, name_len);
> -	full_name[prefix_len + name_len] = '\0';
> -
> -	retval = v9fs_xattr_get(dentry, full_name, buffer, size);
> -	kfree(full_name);
> -	return retval;
> +	return v9fs_xattr_get(dentry, full_name, buffer, size);
>  }
>  

I look strange, to expect that name argument passed to ->get() will have
the full name details. In any case this need more documentation and a
helper as Christoph suggested

-aneesh



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