linux-kernel - Re: [PATCH 5.4 3/5] cifs: Introduce helpers for finding TCP connection

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Date:   Mon, 26 Jun 2023 11:34:44 +0530
From:   Shyam Prasad N <nspmangalore@...il.com>
To:     Rishabh Bhatnagar <risbhat@...zon.com>
Cc:     gregkh@...uxfoundation.org, pc@....nz, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-cifs@...r.kernel.org,
        Aurelien Aptel <aaptel@...e.com>,
        Steve French <stfrench@...rosoft.com>
Subject: Re: [PATCH 5.4 3/5] cifs: Introduce helpers for finding TCP connection

On Sat, Jun 24, 2023 at 3:14 AM Rishabh Bhatnagar <risbhat@...zon.com> wrote:
>
> From: "Paulo Alcantara (SUSE)" <pc@....nz>
>
> commit 345c1a4a9e09dc5842b7bbb6728a77910db69c52 upstream.
>
> Add helpers for finding TCP connections that are good candidates for
> being used by DFS refresh worker.
>
> Signed-off-by: Paulo Alcantara (SUSE) <pc@....nz>
> Reviewed-by: Aurelien Aptel <aaptel@...e.com>
> Signed-off-by: Steve French <stfrench@...rosoft.com>
> Signed-off-by: Rishabh Bhatnagar <risbhat@...zon.com>
> ---
>  fs/cifs/dfs_cache.c | 44 +++++++++++++++++++++++++++++++-------------
>  1 file changed, 31 insertions(+), 13 deletions(-)
>
> diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
> index 3ca65051b55c..31b3dc09e109 100644
> --- a/fs/cifs/dfs_cache.c
> +++ b/fs/cifs/dfs_cache.c
> @@ -1305,6 +1305,30 @@ static char *get_dfs_root(const char *path)
>         return npath;
>  }
>
> +static inline void put_tcp_server(struct TCP_Server_Info *server)
> +{
> +       cifs_put_tcp_session(server, 0);
> +}
> +
> +static struct TCP_Server_Info *get_tcp_server(struct smb_vol *vol)
> +{
> +       struct TCP_Server_Info *server;
> +
> +       server = cifs_find_tcp_session(vol);
> +       if (IS_ERR_OR_NULL(server))
> +               return NULL;
> +
> +       spin_lock(&GlobalMid_Lock);
> +       if (server->tcpStatus != CifsGood) {
> +               spin_unlock(&GlobalMid_Lock);
> +               put_tcp_server(server);
> +               return NULL;
> +       }
> +       spin_unlock(&GlobalMid_Lock);

We've moved away from using GlobalMid_Lock for anything other than MIDs.
Please use server->srv_lock instead.

> +
> +       return server;
> +}
> +
>  /* Find root SMB session out of a DFS link path */
>  static struct cifs_ses *find_root_ses(struct vol_info *vi,
>                                       struct cifs_tcon *tcon,
> @@ -1347,13 +1371,8 @@ static struct cifs_ses *find_root_ses(struct vol_info *vi,
>                 goto out;
>         }
>
> -       server = cifs_find_tcp_session(&vol);
> -       if (IS_ERR_OR_NULL(server)) {
> -               ses = ERR_PTR(-EHOSTDOWN);
> -               goto out;
> -       }
> -       if (server->tcpStatus != CifsGood) {
> -               cifs_put_tcp_session(server, 0);
> +       server = get_tcp_server(&vol);
> +       if (!server) {
>                 ses = ERR_PTR(-EHOSTDOWN);
>                 goto out;
>         }
> @@ -1451,19 +1470,18 @@ static void refresh_cache_worker(struct work_struct *work)
>         mutex_lock(&vol_lock);
>
>         list_for_each_entry(vi, &vol_list, list) {
> -               server = cifs_find_tcp_session(&vi->smb_vol);
> -               if (IS_ERR_OR_NULL(server))
> +               server = get_tcp_server(&vi->smb_vol);
> +               if (!server)
>                         continue;
> -               if (server->tcpStatus != CifsGood)
> -                       goto next;
> +
>                 get_tcons(server, &list);
>                 list_for_each_entry_safe(tcon, ntcon, &list, ulist) {
>                         refresh_tcon(vi, tcon);
>                         list_del_init(&tcon->ulist);
>                         cifs_put_tcon(tcon);
>                 }
> -next:
> -               cifs_put_tcp_session(server, 0);
> +
> +               put_tcp_server(server);
>         }
>         queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
>         mutex_unlock(&vol_lock);
> --
> 2.40.1
>


-- 
Regards,
Shyam