[2/2] cifs: Add a laundromat thread that will timeout any directory leases we have

after a timeout of 5 seconds. Later we will add instrumentation to tweak this value.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
---
 fs/cifs/cached_dir.c | 70 ++++++++++++++++++++++++++++++++++++++++++++
 fs/cifs/cached_dir.h |  1 +
 2 files changed, 71 insertions(+)

fixing minor whitespace error and tentatively pushed to cifs-2.6.git
for-next pending testing

On Thu, Sep 22, 2022 at 7:56 PM Ronnie Sahlberg <lsahlber@redhat.com> wrote:
>
> after a timeout of 5 seconds. Later we will add instrumentation to tweak this value.
>
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/cached_dir.c | 70 ++++++++++++++++++++++++++++++++++++++++++++
>  fs/cifs/cached_dir.h |  1 +
>  2 files changed, 71 insertions(+)
>
> diff --git a/fs/cifs/cached_dir.c b/fs/cifs/cached_dir.c
> index e2f2052dbabf..ffe0dea08b17 100644
> --- a/fs/cifs/cached_dir.c
> +++ b/fs/cifs/cached_dir.c
> @@ -95,6 +95,7 @@ path_to_dentry(struct cifs_sb_info *cifs_sb, const char *path)
>                 dput(dentry);
>                 dentry = child;
>         } while (!IS_ERR(dentry));
> +
>         return dentry;
>  }
>
> @@ -498,6 +499,55 @@ static void free_cached_dir(struct cached_fid *cfid)
>         kfree(cfid);
>  }
>
> +
> +
> +static int
> +cifs_cfids_laundromat_thread(void *p)
> +{
> +       struct cached_fids *cfids = p;
> +       struct cached_fid *cfid, *q;
> +       struct list_head entry;
> +
> +       while (!kthread_should_stop()) {
> +               ssleep(1);
> +               INIT_LIST_HEAD(&entry);
> +               if (kthread_should_stop())
> +                       return 0;
> +               spin_lock(&cfids->cfid_list_lock);
> +               list_for_each_entry_safe(cfid, q, &cfids->entries, entry) {
> +                       if (time_after(jiffies, cfid->time + HZ * 5)) {
> +                               list_del(&cfid->entry);
> +                               list_add(&cfid->entry, &entry);
> +                               cfids->num_entries--;
> +                       }
> +               }
> +               spin_unlock(&cfids->cfid_list_lock);
> +
> +               list_for_each_entry_safe(cfid, q, &entry, entry) {
> +                       cfid->on_list = false;
> +                       list_del(&cfid->entry);
> +                       /*
> +                        * Cancel, and wait for the work to finish in
> +                        * case we are racing with it.
> +                        */
> +                       cancel_work_sync(&cfid->lease_break);
> +                       if (cfid->has_lease) {
> +                               /*
> +                                * We lease has not yet been cancelled from
> +                                * the server so we need to drop the reference.
> +                                */
> +                               spin_lock(&cfids->cfid_list_lock);
> +                               cfid->has_lease = false;
> +                               spin_unlock(&cfids->cfid_list_lock);
> +                               kref_put(&cfid->refcount, smb2_close_cached_fid);
> +                       }
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +
>  struct cached_fids *init_cached_dirs(void)
>  {
>         struct cached_fids *cfids;
> @@ -507,6 +557,20 @@ struct cached_fids *init_cached_dirs(void)
>                 return NULL;
>         spin_lock_init(&cfids->cfid_list_lock);
>         INIT_LIST_HEAD(&cfids->entries);
> +
> +       /*
> +        * since we're in a cifs function already, we know that
> +        * this will succeed. No need for try_module_get().
> +        */
> +       __module_get(THIS_MODULE);
> +       cfids->laundromat = kthread_run(cifs_cfids_laundromat_thread,
> +                                 cfids, "cifsd-cfid-laundromat");
> +       if (IS_ERR(cfids->laundromat)) {
> +               cifs_dbg(VFS, "Failed to start cfids laundromat thread.\n");
> +               kfree(cfids);
> +               module_put(THIS_MODULE);
> +               return NULL;
> +       }
>         return cfids;
>  }
>
> @@ -519,6 +583,12 @@ void free_cached_dirs(struct cached_fids *cfids)
>         struct cached_fid *cfid, *q;
>         struct list_head entry;
>
> +       if (cfids->laundromat) {
> +               kthread_stop(cfids->laundromat);
> +               cfids->laundromat = NULL;
> +               module_put(THIS_MODULE);
> +       }
> +
>         INIT_LIST_HEAD(&entry);
>         spin_lock(&cfids->cfid_list_lock);
>         list_for_each_entry_safe(cfid, q, &cfids->entries, entry) {
> diff --git a/fs/cifs/cached_dir.h b/fs/cifs/cached_dir.h
> index e536304ca2ce..4ab9b10cd098 100644
> --- a/fs/cifs/cached_dir.h
> +++ b/fs/cifs/cached_dir.h
> @@ -57,6 +57,7 @@ struct cached_fids {
>         spinlock_t cfid_list_lock;
>         int num_entries;
>         struct list_head entries;
> +       struct task_struct *laundromat;
>  };
>
>  extern struct cached_fids *init_cached_dirs(void);
> --
> 2.35.3
>