erofs: unify inline/shared xattr iterators for listxattr/getxattr

Make inline_{list,get}xattr() as well as inline_xattr_iter_begin()
unified as erofs_xattr_iter_inline(), and shared_{list,get}xattr()
unified as erofs_xattr_iter_shared().

After these changes, both erofs_xattr_iter_{inline,shared}() 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>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230613074114.120115-5-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Author: lostjeffle

fs/erofs/xattr.c

@@ -139,27 +139,6 @@ 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;
-
-	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;
-	}
-
-	it->pos = erofs_iloc(inode) + vi->inode_isize + xattr_header_sz;
-	it->kaddr = erofs_bread(&it->buf, erofs_blknr(it->sb, it->pos),
-				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
  * `pos' pointing to the next xattr item rather than an arbitrary position.
@@ -333,47 +312,6 @@ 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;
-	struct erofs_sb_info *sbi = EROFS_SB(sb);
-	unsigned int i;
-	int ret = -ENOATTR;
-
-	for (i = 0; i < vi->xattr_shared_count; ++i) {
-		it->pos = erofs_pos(sb, sbi->xattr_blkaddr) +
-				vi->xattr_shared_xattrs[i] * sizeof(__le32);
-		it->kaddr = erofs_bread(&it->buf, erofs_blknr(sb, it->pos),
-					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);
@@ -384,39 +322,6 @@ 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)
@@ -521,32 +426,49 @@ static const struct xattr_iter_handlers list_xattr_handlers = {
 	.value = NULL
 };
 
-static int inline_listxattr(struct erofs_xattr_iter *it)
+static int erofs_xattr_iter_inline(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;
 	int ret;
-	unsigned int remaining;
 
-	ret = inline_xattr_iter_begin(it, d_inode(it->dentry));
-	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;
+	}
+
+	it->pos = erofs_iloc(inode) + vi->inode_isize + xattr_header_sz;
+	it->kaddr = erofs_bread(&it->buf, erofs_blknr(it->sb, it->pos),
+				EROFS_KMAP);
+	if (IS_ERR(it->kaddr))
+		return PTR_ERR(it->kaddr);
+
+	remaining = vi->xattr_isize - xattr_header_sz;
+	op = getxattr ? &find_xattr_handlers : &list_xattr_handlers;
 
-	remaining = ret;
 	while (remaining) {
-		ret = xattr_foreach(it, &list_xattr_handlers, &remaining);
-		if (ret)
+		ret = xattr_foreach(it, op, &remaining);
+		if ((getxattr && ret != -ENOATTR) || (!getxattr && ret))
 			break;
 	}
-	return ret ? ret : it->buffer_ofs;
+	return ret;
 }
 
-static int shared_listxattr(struct erofs_xattr_iter *it)
+static int erofs_xattr_iter_shared(struct erofs_xattr_iter *it,
+				   struct inode *inode, bool getxattr)
 {
-	struct inode *const inode = d_inode(it->dentry);
 	struct erofs_inode *const vi = EROFS_I(inode);
 	struct super_block *const sb = it->sb;
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
 	unsigned int i;
-	int ret = 0;
+	const struct xattr_iter_handlers *op;
+	int ret = -ENOATTR;
+
+	op = getxattr ? &find_xattr_handlers : &list_xattr_handlers;
 
 	for (i = 0; i < vi->xattr_shared_count; ++i) {
 		it->pos = erofs_pos(sb, sbi->xattr_blkaddr) +
@@ -556,20 +478,52 @@ static int shared_listxattr(struct erofs_xattr_iter *it)
 		if (IS_ERR(it->kaddr))
 			return PTR_ERR(it->kaddr);
 
-		ret = xattr_foreach(it, &list_xattr_handlers, NULL);
-		if (ret)
+		ret = xattr_foreach(it, op, NULL);
+		if ((getxattr && ret != -ENOATTR) || (!getxattr && ret))
 			break;
 	}
-	return ret ? ret : it->buffer_ofs;
+	return ret;
 }
 
-ssize_t erofs_listxattr(struct dentry *dentry,
-			char *buffer, size_t buffer_size)
+int erofs_getxattr(struct inode *inode, int index, const char *name,
+		   void *buffer, size_t buffer_size)
 {
 	int ret;
 	struct erofs_xattr_iter it;
 
-	ret = erofs_init_inode_xattrs(d_inode(dentry));
+	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 = erofs_xattr_iter_inline(&it, inode, true);
+	if (ret == -ENOATTR)
+		ret = erofs_xattr_iter_shared(&it, inode, true);
+	erofs_put_metabuf(&it.buf);
+	return ret ? ret : it.buffer_ofs;
+}
+
+ssize_t erofs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
+{
+	int ret;
+	struct erofs_xattr_iter it;
+	struct inode *inode = d_inode(dentry);
+
+	ret = erofs_init_inode_xattrs(inode);
 	if (ret == -ENOATTR)
 		return 0;
 	if (ret)
@@ -583,11 +537,13 @@ ssize_t erofs_listxattr(struct dentry *dentry,
 	it.buffer_size = buffer_size;
 	it.buffer_ofs = 0;
 
-	ret = inline_listxattr(&it);
-	if (ret >= 0 || ret == -ENOATTR)
-		ret = shared_listxattr(&it);
+	ret = erofs_xattr_iter_inline(&it, inode, false);
+	if (!ret || ret == -ENOATTR)
+		ret = erofs_xattr_iter_shared(&it, inode, false);
+	if (ret == -ENOATTR)
+		ret = 0;
 	erofs_put_metabuf(&it.buf);
-	return ret;
+	return ret ? ret : it.buffer_ofs;
 }
 
 void erofs_xattr_prefixes_cleanup(struct super_block *sb)