Re: [PATCH 1/2] erofs: simplify instantiation of pseudo mount in fscache mode

Gao Xiang
2023-02-03T07:14:11Z

On 2023/2/3 11:47, Jingbo Xu wrote:
> Introduce a pseudo fs type dedicated to the pseudo mount of fscache
> mode, so that the logic of real mount won't be messed up with that of
> pseudo mount, making the implementation of fscache mode more
> self-contained.
>
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
> fs/erofs/fscache.c | 46 +++++++++++++++++++++++++++------------------
> fs/erofs/internal.h | 6 ++++++
> fs/erofs/super.c | 35 +++++++---------------------------
> 3 files changed, 41 insertions(+), 46 deletions(-)
>
> diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> index af6ba52bbe8b..2eb42bbc56a4 100644
> --- a/fs/erofs/fscache.c
> +++ b/fs/erofs/fscache.c
> @@ -6,12 +6,13 @@
> #include <linux/fscache.h>
> #include <linux/file.h>
> #include <linux/anon_inodes.h>
> +#include <linux/pseudo_fs.h>
> #include "internal.h"
>
> static DEFINE_MUTEX(erofs_domain_list_lock);
> static DEFINE_MUTEX(erofs_domain_cookies_lock);
> static LIST_HEAD(erofs_domain_list);
> -static struct vfsmount *erofs_pseudo_mnt;
> +static struct vfsmount *erofs_pseudo_mnt __read_mostly;
>
> struct erofs_fscache_request {
> struct erofs_fscache_request *primary;
> @@ -471,10 +472,6 @@ static void erofs_fscache_domain_put(struct erofs_domain *domain)
> mutex_lock(&erofs_domain_list_lock);
> if (refcount_dec_and_test(&domain->ref)) {
> list_del(&domain->list);
> - if (list_empty(&erofs_domain_list)) {
> - kern_unmount(erofs_pseudo_mnt);
> - erofs_pseudo_mnt = NULL;
> - }
> mutex_unlock(&erofs_domain_list_lock);
> fscache_relinquish_volume(domain->volume, NULL, false);
> kfree(domain->domain_id);
> @@ -526,15 +523,10 @@ static int erofs_fscache_init_domain(struct super_block *sb)
> }
>
> err = erofs_fscache_register_volume(sb);
> - if (err)
> - goto out;
> -
> - if (!erofs_pseudo_mnt) {
> - erofs_pseudo_mnt = kern_mount(&erofs_fs_type);
> - if (IS_ERR(erofs_pseudo_mnt)) {
> - err = PTR_ERR(erofs_pseudo_mnt);
> - goto out;
> - }
> + if (err) {
> + kfree(domain->domain_id);
> + kfree(domain);
> + return err;
> }
>
> domain->volume = sbi->volume;
> @@ -542,10 +534,6 @@ static int erofs_fscache_init_domain(struct super_block *sb)
> list_add(&domain->list, &erofs_domain_list);
> sbi->domain = domain;
> return 0;
> -out:
> - kfree(domain->domain_id);
> - kfree(domain);
> - return err;
> }
>
> static int erofs_fscache_register_domain(struct super_block *sb)
> @@ -780,3 +768,25 @@ void erofs_fscache_unregister_fs(struct super_block *sb)
> sbi->volume = NULL;
> sbi->domain = NULL;
> }
> +
> +static int erofs_fc_anon_get_tree(struct fs_context *fc)
> +{
> + return PTR_ERR_OR_ZERO(init_pseudo(fc, EROFS_SUPER_MAGIC));
> +}
> +
> +int __init erofs_fscache_init(void)
> +{
> + static struct file_system_type erofs_anon_fs = {
> + .name = "erofs_anonfs",
> + .init_fs_context = erofs_fc_anon_get_tree,
> + .kill_sb = kill_anon_super,
> + };

Please don't add another filesystem type, thanks.

Thanks,
Gao Xiang