On Wed, Aug 31, 2022 at 08:31:22PM +0800, Jia Zhu wrote:
> A new fscache-based shared domain mode is going to be introduced for
> erofs. In which case, same data blobs in same domain will be shared
> and reused to reduce on-disk space usage.
>
> As the first step, we use pseudo mnt to manage and maintain domain's
> lifecycle.
>
> The implementation of sharing blobs will be introduced in subsequent
> patches.
>
> Signed-off-by: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
> ---
> fs/erofs/Makefile | 2 +-
> fs/erofs/domain.c | 115 ++++++++++++++++++++++++++++++++++++++++++++
> fs/erofs/fscache.c | 10 +++-
> fs/erofs/internal.h | 20 +++++++-
> fs/erofs/super.c | 17 ++++---
> 5 files changed, 154 insertions(+), 10 deletions(-)
> create mode 100644 fs/erofs/domain.c
>
> diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile
> index 99bbc597a3e9..a4af7ecf636f 100644
> --- a/fs/erofs/Makefile
> +++ b/fs/erofs/Makefile
> @@ -5,4 +5,4 @@ erofs-objs := super.o inode.o data.o namei.o dir.o utils.o pcpubuf.o sysfs.o
> erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
> erofs-$(CONFIG_EROFS_FS_ZIP) += decompressor.o zmap.o zdata.o
> erofs-$(CONFIG_EROFS_FS_ZIP_LZMA) += decompressor_lzma.o
> -erofs-$(CONFIG_EROFS_FS_ONDEMAND) += fscache.o
> +erofs-$(CONFIG_EROFS_FS_ONDEMAND) += fscache.o domain.o
> diff --git a/fs/erofs/domain.c b/fs/erofs/domain.c
> new file mode 100644
> index 000000000000..6461e4ee3582
> --- /dev/null
> +++ b/fs/erofs/domain.c
`domain` is now still entirely designed for fscache backend.
I'd suggest moving the code below to fscache.c for now until we
could find more use cases more than fscache.
> @@ -0,0 +1,115 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022, Bytedance Inc. All rights reserved.
Also you could move this line to fscache.c as well.
> + */
> +
> +#include <linux/pseudo_fs.h>
> +#include <linux/fs_context.h>
> +#include <linux/magic.h>
> +#include <linux/fscache.h>
> +
> +#include "internal.h"
> +
> +static DEFINE_SPINLOCK(erofs_domain_list_lock);
> +static LIST_HEAD(erofs_domain_list);
> +
> +void erofs_fscache_domain_get(struct erofs_domain *domain)
> +{
> + if (!domain)
> + return;
> + refcount_inc(&domain->ref);
> +}
> +
> +void erofs_fscache_domain_put(struct erofs_domain *domain)
> +{
> + if (!domain)
> + return;
> + if (refcount_dec_and_test(&domain->ref)) {
> + fscache_relinquish_volume(domain->volume, NULL, false);
> + spin_lock(&erofs_domain_list_lock);
> + list_del(&domain->list);
> + spin_unlock(&erofs_domain_list_lock);
> + kern_unmount(domain->mnt);
> + kfree(domain->domain_id);
> + kfree(domain);
> + }
> +}
> +
> +static int anon_inodefs_init_fs_context(struct fs_context *fc)
> +{
> + struct pseudo_fs_context *ctx = init_pseudo(fc, ANON_INODE_FS_MAGIC);
> +
> + if (!ctx)
> + return -ENOMEM;
> + return 0;
> +}
> +
> +static struct file_system_type anon_inode_fs_type = {
> + .name = "pseudo_domainfs",
> + .init_fs_context = anon_inodefs_init_fs_context,
> + .kill_sb = kill_anon_super,
> +};
Could we just use erofs filesystem type but with a special sb instead?
No need to cause messes like this.
Thanks,
Gao Xiang
