linux-kernel - Re: [PATCH v6 12/22] erofs: add cookie context helper functions

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Date:   Fri, 25 Mar 2022 21:41:42 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Jeffle Xu <jefflexu@...ux.alibaba.com>
Cc:     dhowells@...hat.com, linux-cachefs@...hat.com, xiang@...nel.org,
        chao@...nel.org, linux-erofs@...ts.ozlabs.org,
        torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
        willy@...radead.org, linux-fsdevel@...r.kernel.org,
        joseph.qi@...ux.alibaba.com, bo.liu@...ux.alibaba.com,
        tao.peng@...ux.alibaba.com, gerry@...ux.alibaba.com,
        eguan@...ux.alibaba.com, linux-kernel@...r.kernel.org,
        luodaowen.backend@...edance.com, tianzichen@...ishou.com,
        fannaihao@...du.com
Subject: Re: [PATCH v6 12/22] erofs: add cookie context helper functions

Hi Jeffle,

On Fri, Mar 25, 2022 at 08:22:13PM +0800, Jeffle Xu wrote:
> Introduce "struct erofs_fscache" for managing cookie for backinig file,
> and helper functions for initializing and cleaning up this context
> structure.
> 
> Signed-off-by: Jeffle Xu <jefflexu@...ux.alibaba.com>
> ---
>  fs/erofs/fscache.c  | 61 +++++++++++++++++++++++++++++++++++++++++++++
>  fs/erofs/internal.h | 14 +++++++++++
>  2 files changed, 75 insertions(+)
> 
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index 08cf570a0810..73235fd43bf6 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -7,6 +7,67 @@
>  
>  static struct fscache_volume *volume;
>  
> +static int erofs_fscache_init_cookie(struct erofs_fscache *ctx, char *path)
> +{
> +	struct fscache_cookie *cookie;
> +
> +	cookie = fscache_acquire_cookie(volume, FSCACHE_ADV_WANT_CACHE_SIZE,
> +					path, strlen(path),
> +					NULL, 0, 0);

It'd be better to rearrange in one line?

					path, strlen(path), NULL, 0, 0);

> +	if (!cookie)
> +		return -EINVAL;
> +
> +	fscache_use_cookie(cookie, false);
> +	ctx->cookie = cookie;
> +	return 0;
> +}
> +
> +static inline void erofs_fscache_cleanup_cookie(struct erofs_fscache *ctx)
> +{
> +	struct fscache_cookie *cookie = ctx->cookie;
> +
> +	fscache_unuse_cookie(cookie, NULL, NULL);
> +	fscache_relinquish_cookie(cookie, false);
> +	ctx->cookie = NULL;
> +}
> +
> +/*
> + * erofs_fscache_get - create an fscache context for blob file
> + * @sb:		superblock
> + * @path:	name of blob file
> + *
> + * Return: fscache context on success, ERR_PTR() on failure.
> + */
> +struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path)

erofs_fscache_register?

> +{
> +	struct erofs_fscache *ctx;
> +	int ret;
> +
> +	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ret = erofs_fscache_init_cookie(ctx, path);

Can we fold it here? No need to introduce such simple wrapper..

> +	if (ret) {
> +		erofs_err(sb, "failed to init cookie");

It would be better to print the path?

> +		goto err;

		kfree(ctx);
		return ERR_PTR(ret);

At least for now.

> +	}
> +
> +	return ctx;
> +err:
> +	kfree(ctx);
> +	return ERR_PTR(ret);
> +}
> +
> +void erofs_fscache_put(struct erofs_fscache *ctx)

erofs_fscache_unregister?

> +{
> +	if (!ctx)
> +		return;
> +
> +	erofs_fscache_cleanup_cookie(ctx);

Fold it too, since such helper doesn't simplify code a lot but need
to take one more time to redirect..

Thanks,
Gao Xiang

> +	kfree(ctx);
> +}
> +
>  int __init erofs_init_fscache(void)
>  {
>  	volume = fscache_acquire_volume("erofs", NULL, NULL, 0);
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 45b8b0dd8a27..d4f2b43cedae 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -96,6 +96,10 @@ struct erofs_sb_lz4_info {
>  	u16 max_pclusterblks;
>  };
>  
> +struct erofs_fscache {
> +	struct fscache_cookie *cookie;
> +};
> +
>  struct erofs_sb_info {
>  	struct erofs_mount_opts opt;	/* options */
>  #ifdef CONFIG_EROFS_FS_ZIP
> @@ -620,9 +624,19 @@ static inline int z_erofs_load_lzma_config(struct super_block *sb,
>  #ifdef CONFIG_EROFS_FS_ONDEMAND
>  int erofs_init_fscache(void);
>  void erofs_exit_fscache(void);
> +
> +struct erofs_fscache *erofs_fscache_get(struct super_block *sb, char *path);
> +void erofs_fscache_put(struct erofs_fscache *ctx);
>  #else
>  static inline int erofs_init_fscache(void) { return 0; }
>  static inline void erofs_exit_fscache(void) {}
> +
> +static inline struct erofs_fscache *erofs_fscache_get(struct super_block *sb,
> +						      char *path)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}
> +static inline void erofs_fscache_put(struct erofs_fscache *ctx) {}
>  #endif
>  
>  #define EFSCORRUPTED    EUCLEAN         /* Filesystem is corrupted */
> -- 
> 2.27.0