Re: [PATCH v6 05/24] erofs: add inode operations

Christoph Hellwig
2019-08-29T10:24:40Z

On Fri, Aug 02, 2019 at 08:53:28PM +0800, Gao Xiang wrote:
> This adds core functions to get, read an inode.
> It adds statx support as well.
>
> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
> ---
> fs/erofs/inode.c | 291 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 291 insertions(+)
> create mode 100644 fs/erofs/inode.c
>
> diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
> new file mode 100644
> index 000000000000..b6ea997bc4ae
> --- /dev/null
> +++ b/fs/erofs/inode.c
> @@ -0,0 +1,291 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * linux/fs/erofs/inode.c
> + *
> + * Copyright (C) 2017-2018 HUAWEI, Inc.
> + * http://www.huawei.com/
> + * Created by Gao Xiang <gaoxiang25@huawei.com>
> + */
> +#include "internal.h"
> +
> +#include <trace/events/erofs.h>
> +
> +/* no locking */
> +static int read_inode(struct inode *inode, void *data)
> +{
> + struct erofs_vnode *vi = EROFS_V(inode);
> + struct erofs_inode_v1 *v1 = data;
> + const unsigned int advise = le16_to_cpu(v1->i_advise);
> + erofs_blk_t nblks = 0;
> +
> + vi->datamode = __inode_data_mapping(advise);

What is the deal with these magic underscores here and various
other similar helpers?

> + /* fast symlink (following ext4) */

This actually originates in FFS. But it is so common that the comment
seems a little pointless.

> + if (S_ISLNK(inode->i_mode) && inode->i_size < PAGE_SIZE) {
> + char *lnk = erofs_kmalloc(sbi, inode->i_size + 1, GFP_KERNEL);

Please just use plain kmalloc everywhere and let the normal kernel
error injection code take care of injeting any errors.

> + /* inline symlink data shouldn't across page boundary as well */

... should not cross ..

> + if (unlikely(m_pofs + inode->i_size > PAGE_SIZE)) {
> + DBG_BUGON(1);
> + kfree(lnk);
> + return -EIO;
> + }
> +
> + /* get in-page inline data */

s/get/copy/, but the comment seems rather pointless.

> + memcpy(lnk, data + m_pofs, inode->i_size);
> + lnk[inode->i_size] = '\0';
> +
> + inode->i_link = lnk;
> + set_inode_fast_symlink(inode);

Please just set the ops directly instead of obsfucating that in a single
caller, single line inline function. And please set it instead of the
normal symlink iops in the same place where you also set those.:w

> + err = read_inode(inode, data + ofs);
> + if (!err) {

if (err)
goto out_unlock;

.. and save one level of indentation.

> + if (is_inode_layout_compression(inode)) {

The name of this helper is a little odd. But I think just
opencoding it seems generally cleaner anyway.

> + err = -ENOTSUPP;
> + goto out_unlock;
> + }
> +
> + inode->i_mapping->a_ops = &erofs_raw_access_aops;
> +
> + /* fill last page if inline data is available */
> + err = fill_inline_data(inode, data, ofs);

Well, I think you should move the is_inode_flat_inline and
(S_ISLNK(inode->i_mode) && inode->i_size < PAGE_SIZE) checks from that
helper here, as otherwise you make everyone wonder why you'd always
fill out the inline data.

> +static inline struct inode *erofs_iget_locked(struct super_block *sb,
> + erofs_nid_t nid)
> +{
> + const unsigned long hashval = erofs_inode_hash(nid);
> +
> +#if BITS_PER_LONG >= 64
> + /* it is safe to use iget_locked for >= 64-bit platform */
> + return iget_locked(sb, hashval);
> +#else
> + return iget5_locked(sb, hashval, erofs_ilookup_test_actor,
> + erofs_iget_set_actor, &nid);
> +#endif

Just use the slightly more complicated 32-bit version everywhere so that
you have a single actually tested code path. And then remove this
helper.