Re: [PATCH 04/11] cifs: serialize channel reconnects

[Steve French <smfrench@gmail.com>]

Paulo had a few comments on patch 3 of the series, so have applied the
first two, and will wait on patch 3 and 4, but tentatively merged the
first two:

a7c73e3d5842 (HEAD -> for-next, origin/for-next) cifs: generate
signkey for the channel that's reconnecting
d169aadd50c7 cifs: fix tcon status change after tree connect

On Fri, Mar 10, 2023 at 9:33 AM Shyam Prasad N <nspmangalore@gmail.com> wrote:
>
> Parallel session reconnects are prone to race conditions
> that are difficult to avoid cleanly. The changes so far do
> ensure that parallel reconnects eventually go through.
> But that can take multiple session setups on the same channel.
>
> Avoiding that by serializing the session setups on parallel
> channels. In doing so, we should avoid such issues.
>
> Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
> ---
>  fs/cifs/connect.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 7b103f69432e..4ea1e51c3fa5 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -222,6 +222,11 @@ cifs_mark_tcp_ses_conns_for_reconnect(struct TCP_Server_Info *server,
>                 else
>                         cifs_chan_set_need_reconnect(ses, server);
>
> +               cifs_dbg(FYI, "%s: channel connect bitmaps: 0x%lx 0x%lx\n",
> +                        __func__,
> +                        ses->chans_need_reconnect,
> +                        ses->chans_in_reconnect);
> +
>                 /* If all channels need reconnect, then tcon needs reconnect */
>                 if (!mark_smb_session && !CIFS_ALL_CHANS_NEED_RECONNECT(ses)) {
>                         spin_unlock(&ses->chan_lock);
> @@ -3744,6 +3749,11 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
>         retries = 5;
>
>         spin_lock(&ses->ses_lock);
> +       cifs_dbg(FYI, "%s: channel connect bitmaps: 0x%lx 0x%lx\n",
> +                __func__,
> +                ses->chans_need_reconnect,
> +                ses->chans_in_reconnect);
> +
>         if (ses->ses_status != SES_GOOD &&
>             ses->ses_status != SES_NEW &&
>             ses->ses_status != SES_NEED_RECON) {
> @@ -3762,11 +3772,11 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
>         }
>
>         /* another process is in the processs of sess setup */
> -       while (cifs_chan_in_reconnect(ses, server)) {
> +       while (ses->chans_in_reconnect) {
>                 spin_unlock(&ses->chan_lock);
>                 spin_unlock(&ses->ses_lock);
>                 rc = wait_event_interruptible_timeout(ses->reconnect_q,
> -                                                     (!cifs_chan_in_reconnect(ses, server)),
> +                                                     (!ses->chans_in_reconnect),
>                                                       HZ);
>                 if (rc < 0) {
>                         cifs_dbg(FYI, "%s: aborting sess setup due to a received signal by the process\n",
> @@ -3776,8 +3786,8 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses,
>                 spin_lock(&ses->ses_lock);
>                 spin_lock(&ses->chan_lock);
>
> -               /* are we still trying to reconnect? */
> -               if (!cifs_chan_in_reconnect(ses, server)) {
> +               /* did the bitmask change? */
> +               if (!ses->chans_in_reconnect) {
>                         spin_unlock(&ses->chan_lock);
>                         spin_unlock(&ses->ses_lock);
>                         goto check_again;
> --
> 2.34.1
>


-- 
Thanks,

Steve