On 12/27/21 8:54 PM, Jeffle Xu wrote:
> fscache/cachefiles used to serve as a local cache for remote fs. The
> following patches will introduce a new use case, in which local
> read-only fs could implement demand reading with fscache. By then the
> user daemon needs to read and poll on the devnode, and thus the original
> cachefiles devnode can't be reused in this case.
>
> Thus create a new devnode specifically for the new mode. The following
> patches will add more file_operations.
>
> Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> ---
> fs/cachefiles/daemon.c | 8 ++++++++
> fs/cachefiles/internal.h | 1 +
> fs/cachefiles/main.c | 12 ++++++++++++
> 3 files changed, 21 insertions(+)
>
> diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
> index 40a792421fc1..871f1e0f423d 100644
> --- a/fs/cachefiles/daemon.c
> +++ b/fs/cachefiles/daemon.c
> @@ -56,6 +56,14 @@ const struct file_operations cachefiles_daemon_fops = {
> .llseek = noop_llseek,
> };
>
> +const struct file_operations cachefiles_demand_fops = {
> + .owner = THIS_MODULE,
> + .open = cachefiles_daemon_open,
> + .release = cachefiles_daemon_release,
> + .write = cachefiles_daemon_write,
> + .llseek = noop_llseek,
> +};
> +
Better to prepare the on-demand read() and poll() first, and then add
the on-demand cachefiles dev.
Thanks,
Joseph
> struct cachefiles_daemon_cmd {
> char name[8];
> int (*handler)(struct cachefiles_cache *cache, char *args);
> diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
> index 421423819d63..e0ed811d628d 100644
> --- a/fs/cachefiles/internal.h
> +++ b/fs/cachefiles/internal.h
> @@ -145,6 +145,7 @@ extern int cachefiles_has_space(struct cachefiles_cache *cache,
> * daemon.c
> */
> extern const struct file_operations cachefiles_daemon_fops;
> +extern const struct file_operations cachefiles_demand_fops;
>
> /*
> * error_inject.c
> diff --git a/fs/cachefiles/main.c b/fs/cachefiles/main.c
> index 3f369c6f816d..0a423274d283 100644
> --- a/fs/cachefiles/main.c
> +++ b/fs/cachefiles/main.c
> @@ -39,6 +39,12 @@ static struct miscdevice cachefiles_dev = {
> .fops = &cachefiles_daemon_fops,
> };
>
> +static struct miscdevice cachefiles_demand_dev = {
> + .minor = MISC_DYNAMIC_MINOR,
> + .name = "cachefiles_demand",
> + .fops = &cachefiles_demand_fops,
> +};
> +
> /*
> * initialise the fs caching module
> */
> @@ -52,6 +58,9 @@ static int __init cachefiles_init(void)
> ret = misc_register(&cachefiles_dev);
> if (ret < 0)
> goto error_dev;
> + ret = misc_register(&cachefiles_demand_dev);
> + if (ret < 0)
> + goto error_demand_dev;
>
> /* create an object jar */
> ret = -ENOMEM;
> @@ -68,6 +77,8 @@ static int __init cachefiles_init(void)
> return 0;
>
> error_object_jar:
> + misc_deregister(&cachefiles_demand_dev);
> +error_demand_dev:
> misc_deregister(&cachefiles_dev);
> error_dev:
> cachefiles_unregister_error_injection();
> @@ -86,6 +97,7 @@ static void __exit cachefiles_exit(void)
> pr_info("Unloading\n");
>
> kmem_cache_destroy(cachefiles_object_jar);
> + misc_deregister(&cachefiles_demand_dev);
> misc_deregister(&cachefiles_dev);
> cachefiles_unregister_error_injection();
> }
--
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