Re: [PATCH v4 4/5] erofs: unify inline/share xattr iterators for listxattr/getxattr

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2023/5/31 11:13, Jingbo Xu wrote:
> Make inline_getxattr() and inline_listxattr() unified as
> iter_inline_xattr(), shared_getxattr() and shared_listxattr() unified as
> iter_shared_xattr().
> 
> After the unification, both iter_inline_xattr() and iter_shared_xattr()
> return 0 on success, and negative error on failure.
> 
> One thing worth noting is that, the logic of returning it->buffer_ofs
> when there's no shared xattrs in shared_listxattr() is moved to
> erofs_listxattr() to make the unification possible.  The only difference
> is that, semantically the old behavior will return ENOATTR rather than
> it->buffer_ofs if ENOATTR encountered when listxattr is parsing upon a
> specific shared xattr, while now the new behavior will return
> it->buffer_ofs in this case.  This is not an issue, as listxattr upon a
> specific xattr won't return ENOATTR.
> 
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
>   fs/erofs/xattr.c | 210 ++++++++++++++++++-----------------------------
>   1 file changed, 78 insertions(+), 132 deletions(-)
> 
> diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
> index 7c76b4d31920..074743e2b271 100644
> --- a/fs/erofs/xattr.c
> +++ b/fs/erofs/xattr.c
> @@ -7,19 +7,6 @@
>   #include <linux/security.h>
>   #include "xattr.h"
>   
> -static inline erofs_blk_t erofs_xattr_blkaddr(struct super_block *sb,
> -					      unsigned int xattr_id)
> -{
> -	return EROFS_SB(sb)->xattr_blkaddr +
> -	       erofs_blknr(sb, xattr_id * sizeof(__u32));
> -}
> -
> -static inline unsigned int erofs_xattr_blkoff(struct super_block *sb,
> -					      unsigned int xattr_id)
> -{
> -	return erofs_blkoff(sb, xattr_id * sizeof(__u32));
> -}
> -
>   struct erofs_xattr_iter {
>   	struct super_block *sb;
>   	struct erofs_buf buf;
> @@ -170,30 +157,6 @@ struct xattr_iter_handlers {
>   		      unsigned int len);
>   };
>   
> -static int inline_xattr_iter_begin(struct erofs_xattr_iter *it,
> -				   struct inode *inode)
> -{
> -	struct erofs_inode *const vi = EROFS_I(inode);
> -	unsigned int xattr_header_sz, inline_xattr_ofs;
> -
> -	xattr_header_sz = sizeof(struct erofs_xattr_ibody_header) +
> -			  sizeof(u32) * vi->xattr_shared_count;
> -	if (xattr_header_sz >= vi->xattr_isize) {
> -		DBG_BUGON(xattr_header_sz > vi->xattr_isize);
> -		return -ENOATTR;
> -	}
> -
> -	inline_xattr_ofs = vi->inode_isize + xattr_header_sz;
> -
> -	it->blkaddr = erofs_blknr(it->sb, erofs_iloc(inode) + inline_xattr_ofs);
> -	it->ofs = erofs_blkoff(it->sb, erofs_iloc(inode) + inline_xattr_ofs);
> -	it->kaddr = erofs_read_metabuf(&it->buf, inode->i_sb, it->blkaddr,
> -				       EROFS_KMAP);
> -	if (IS_ERR(it->kaddr))
> -		return PTR_ERR(it->kaddr);
> -	return vi->xattr_isize - xattr_header_sz;
> -}
> -
>   /*
>    * Regardless of success or failure, `xattr_foreach' will end up with
>    * `ofs' pointing to the next xattr item rather than an arbitrary position.
> @@ -355,46 +318,6 @@ static const struct xattr_iter_handlers find_xattr_handlers = {
>   	.value = xattr_copyvalue
>   };
>   
> -static int inline_getxattr(struct inode *inode, struct erofs_xattr_iter *it)
> -{
> -	int ret;
> -	unsigned int remaining;
> -
> -	ret = inline_xattr_iter_begin(it, inode);
> -	if (ret < 0)
> -		return ret;
> -
> -	remaining = ret;
> -	while (remaining) {
> -		ret = xattr_foreach(it, &find_xattr_handlers, &remaining);
> -		if (ret != -ENOATTR)
> -			break;
> -	}
> -	return ret ? ret : it->buffer_ofs;
> -}
> -
> -static int shared_getxattr(struct inode *inode, struct erofs_xattr_iter *it)
> -{
> -	struct erofs_inode *const vi = EROFS_I(inode);
> -	struct super_block *const sb = it->sb;
> -	unsigned int i, xsid;
> -	int ret = -ENOATTR;
> -
> -	for (i = 0; i < vi->xattr_shared_count; ++i) {
> -		xsid = vi->xattr_shared_xattrs[i];
> -		it->blkaddr = erofs_xattr_blkaddr(sb, xsid);
> -		it->ofs = erofs_xattr_blkoff(sb, xsid);
> -		it->kaddr = erofs_read_metabuf(&it->buf, sb, it->blkaddr, EROFS_KMAP);
> -		if (IS_ERR(it->kaddr))
> -			return PTR_ERR(it->kaddr);
> -
> -		ret = xattr_foreach(it, &find_xattr_handlers, NULL);
> -		if (ret != -ENOATTR)
> -			break;
> -	}
> -	return ret ? ret : it->buffer_ofs;
> -}
> -
>   static bool erofs_xattr_user_list(struct dentry *dentry)
>   {
>   	return test_opt(&EROFS_SB(dentry->d_sb)->opt, XATTR_USER);
> @@ -405,39 +328,6 @@ static bool erofs_xattr_trusted_list(struct dentry *dentry)
>   	return capable(CAP_SYS_ADMIN);
>   }
>   
> -int erofs_getxattr(struct inode *inode, int index,
> -		   const char *name,
> -		   void *buffer, size_t buffer_size)
> -{
> -	int ret;
> -	struct erofs_xattr_iter it;
> -
> -	if (!name)
> -		return -EINVAL;
> -
> -	ret = erofs_init_inode_xattrs(inode);
> -	if (ret)
> -		return ret;
> -
> -	it.index = index;
> -	it.name = (struct qstr)QSTR_INIT(name, strlen(name));
> -	if (it.name.len > EROFS_NAME_LEN)
> -		return -ERANGE;
> -
> -	it.sb = inode->i_sb;
> -	it.buf = __EROFS_BUF_INITIALIZER;
> -	erofs_init_metabuf(&it.buf, it.sb);
> -	it.buffer = buffer;
> -	it.buffer_size = buffer_size;
> -	it.buffer_ofs = 0;
> -
> -	ret = inline_getxattr(inode, &it);
> -	if (ret == -ENOATTR)
> -		ret = shared_getxattr(inode, &it);
> -	erofs_put_metabuf(&it.buf);
> -	return ret;
> -}
> -
>   static int erofs_xattr_generic_get(const struct xattr_handler *handler,
>   				   struct dentry *unused, struct inode *inode,
>   				   const char *name, void *buffer, size_t size)
> @@ -542,45 +432,98 @@ static const struct xattr_iter_handlers list_xattr_handlers = {
>   	.value = NULL
>   };
>   
> -static int inline_listxattr(struct erofs_xattr_iter *it)
> +static int erofs_iter_inline_xattr(struct erofs_xattr_iter *it,
> +				   struct inode *inode, bool getxattr)
>   {
> +	struct erofs_inode *const vi = EROFS_I(inode);
> +	const struct xattr_iter_handlers *op;
> +	unsigned int xattr_header_sz, remaining;
> +	erofs_off_t pos;
>   	int ret;
> -	unsigned int remaining;
>   
> -	ret = inline_xattr_iter_begin(it, d_inode(it->dentry));

In the past, "ret" here is "an int", and
	vi->xattr_isize - xattr_header_sz < 0 will return
negative value (although I think that value is problematic).

see below.


> -	if (ret < 0)
> -		return ret;
> +	xattr_header_sz = sizeof(struct erofs_xattr_ibody_header) +
> +			  sizeof(u32) * vi->xattr_shared_count;
> +	if (xattr_header_sz >= vi->xattr_isize) {
> +		DBG_BUGON(xattr_header_sz > vi->xattr_isize);
> +		return -ENOATTR;
> +	}
> +
> +	pos = erofs_iloc(inode) + vi->inode_isize + xattr_header_sz;
> +	it->blkaddr = erofs_blknr(it->sb, pos);
> +	it->ofs = erofs_blkoff(it->sb, pos);
> +	it->kaddr = erofs_read_metabuf(&it->buf, it->sb, it->blkaddr, EROFS_KMAP);
> +	if (IS_ERR(it->kaddr))
> +		return PTR_ERR(it->kaddr);
> +
> +	remaining = vi->xattr_isize - xattr_header_sz;

so in this patch, `vi->xattr_isize - xattr_header_sz` here could be
negative that should be avoided as well.

Thanks,
Gao Xiang