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Message-ID: <20121025173326.GH11442@htj.dyndns.org>
Date: Thu, 25 Oct 2012 10:33:26 -0700
From: Tejun Heo <tj@...nel.org>
To: Aristeu Rozanski <aris@...hat.com>
Cc: linux-kernel@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
Al Viro <viro@...IV.linux.org.uk>,
linux-fsdevel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH] fs: xattr: rewrite simple_xattr_set()
(cc'ing Hugh and keeping the whole body)
Hello,
On Thu, Oct 25, 2012 at 11:26:14AM -0400, Aristeu Rozanski wrote:
> The way this function was written is confusing and already caused problems.
> Rewriting it to be easier to understand and maintain.
>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Li Zefan <lizefan@...wei.com>
> Cc: Al Viro <viro@...IV.linux.org.uk>
> Signed-off-by: Aristeu Rozanski <aris@...hat.com>
Generally looks okay to me but I think the return value from removal
path is wrong. More below.
> ---
> fs/xattr.c | 124 +++++++++++++++++++++++++++++++++++++------------------------
> 1 file changed, 76 insertions(+), 48 deletions(-)
>
> Index: github/fs/xattr.c
> ===================================================================
> --- github.orig/fs/xattr.c 2012-10-23 16:02:41.155857391 -0400
> +++ github/fs/xattr.c 2012-10-25 11:17:15.118197552 -0400
> @@ -842,55 +842,46 @@
> return ret;
> }
>
> -static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
> - const void *value, size_t size, int flags)
> +static struct simple_xattr *__find_xattr(struct simple_xattrs *xattrs,
> + const char *name)
> {
> struct simple_xattr *xattr;
> - struct simple_xattr *new_xattr = NULL;
> - int err = 0;
> -
> - /* value == NULL means remove */
> - if (value) {
> - new_xattr = simple_xattr_alloc(value, size);
> - if (!new_xattr)
> - return -ENOMEM;
> -
> - new_xattr->name = kstrdup(name, GFP_KERNEL);
> - if (!new_xattr->name) {
> - kfree(new_xattr);
> - return -ENOMEM;
> - }
> - }
>
> - spin_lock(&xattrs->lock);
> list_for_each_entry(xattr, &xattrs->head, list) {
> - if (!strcmp(name, xattr->name)) {
> - if (flags & XATTR_CREATE) {
> - xattr = new_xattr;
> - err = -EEXIST;
> - } else if (new_xattr) {
> - list_replace(&xattr->list, &new_xattr->list);
> - } else {
> - list_del(&xattr->list);
> - }
> - goto out;
> - }
> + if (!strcmp(name, xattr->name))
> + return xattr;
> }
> - if (flags & XATTR_REPLACE) {
> - xattr = new_xattr;
> - err = -ENODATA;
> - } else {
> - list_add(&new_xattr->list, &xattrs->head);
> - xattr = NULL;
> - }
> -out:
> - spin_unlock(&xattrs->lock);
> + return NULL;
> +}
> +
> +static int __simple_xattr_remove(struct simple_xattrs *xattrs,
> + const char *name)
> +{
> + struct simple_xattr *xattr;
> +
> + xattr = __find_xattr(xattrs, name);
> if (xattr) {
> + list_del(&xattr->list);
> kfree(xattr->name);
> kfree(xattr);
> + return 0;
> }
> - return err;
>
> + return 1;
> +}
So, it returns 0 on success and 1 on failure, which in itself isn't a
particularly good idea.
> +
> +/*
> + * xattr REMOVE operation for in-memory/pseudo filesystems
> + */
> +int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
> +{
> + int rc;
> +
> + spin_lock(&xattrs->lock);
> + rc = __simple_xattr_remove(xattrs, name);
> + spin_unlock(&xattrs->lock);
> +
> + return rc;
> }
>
> /**
> @@ -910,17 +901,54 @@
> int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
> const void *value, size_t size, int flags)
> {
> + struct simple_xattr *found, *new_xattr;
> + int err = 0;
> +
> if (size == 0)
> - value = ""; /* empty EA, do not remove */
> - return __simple_xattr_set(xattrs, name, value, size, flags);
> -}
> + value = ""; /* empty EA */
>
> -/*
> - * xattr REMOVE operation for in-memory/pseudo filesystems
> - */
> -int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
> -{
> - return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
> + /* if value == NULL is specified, remove the item */
> + if (value == NULL)
> + return simple_xattr_remove(xattrs, name);
And gets relayed to the caller.
> +
> + new_xattr = simple_xattr_alloc(value, size);
> + if (!new_xattr)
> + return -ENOMEM;
> +
> + new_xattr->name = kstrdup(name, GFP_KERNEL);
> + if (!new_xattr->name) {
> + kfree(new_xattr);
> + return -ENOMEM;
> + }
> +
> + spin_lock(&xattrs->lock);
> +
> + found = __find_xattr(xattrs, name);
> + if (found) {
> + if (flags & XATTR_CREATE) {
> + err = -EEXIST;
> + goto free_new;
> + }
> +
> + list_replace(&found->list, &new_xattr->list);
> + kfree(found->name);
> + kfree(found);
> + } else {
> + if (flags & XATTR_REPLACE) {
> + err = -ENODATA;
> + goto free_new;
> + }
> +
> + list_add_tail(&new_xattr->list, &xattrs->head);
> + }
> +
> +out:
> + spin_unlock(&xattrs->lock);
> + return err;
> +free_new:
> + kfree(new_xattr->name);
> + kfree(new_xattr);
> + goto out;
> }
>
> static bool xattr_is_trusted(const char *name)
--
tejun
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