From: Andreas Gruenbacher <agruenba@redhat.com>
To: Alexander Aring <aahringo@redhat.com>
Cc: gfs2 <gfs2@lists.linux.dev>,
teigland@redhat.com, mark@fasheh.com, jlbec@evilplan.org,
joseph.qi@linux.alibaba.com, ocfs2-devel@lists.linux.dev
Subject: Re: [PATCHv3 v6.5-rc2 2/3] fs: dlm: allow to F_SETLKW getting interrupted
Date: Mon, 25 Mar 2024 16:08:47 +0100 [thread overview]
Message-ID: <CAHc6FU7LBm6RSk_M8BqZRz0LOCmDORKj0bBWSmDjM=3_iB8guQ@mail.gmail.com> (raw)
In-Reply-To: <20230718180721.745569-3-aahringo@redhat.com>
On Tue, Jul 18, 2023 at 8:07 PM Alexander Aring <aahringo@redhat.com> wrote:
> This patch implements dlm plock F_SETLKW interruption feature. If a
> blocking posix lock request got interrupted in user space by a signal a
> cancellation request for a non granted lock request to the user space
> lock manager will be send. The user lock manager answers either with
> zero or a negative errno code. A errno of -ENOENT signals that there is
> currently no blocking lock request waiting to being granted. In case of
> -ENOENT it was probably to late to request a cancellation and the
> pending lock got granted. In any error case we will wait until the lock
> is being granted as cancellation failed, this causes also that in case
> of an older user lock manager returning -EINVAL we will wait as
> cancellation is not supported which should be fine. If a user requires
> this feature the user should update dlm user space to support lock
> request cancellation.
>
> Signed-off-by: Alexander Aring <aahringo@redhat.com>
> ---
> fs/dlm/plock.c | 56 ++++++++++++++++++++++------------
> include/uapi/linux/dlm_plock.h | 1 +
> 2 files changed, 37 insertions(+), 20 deletions(-)
>
> diff --git a/fs/dlm/plock.c b/fs/dlm/plock.c
> index a34f605d8505..a8ffa0760913 100644
> --- a/fs/dlm/plock.c
> +++ b/fs/dlm/plock.c
> @@ -74,30 +74,26 @@ static void send_op(struct plock_op *op)
> wake_up(&send_wq);
> }
>
> -/* If a process was killed while waiting for the only plock on a file,
> - locks_remove_posix will not see any lock on the file so it won't
> - send an unlock-close to us to pass on to userspace to clean up the
> - abandoned waiter. So, we have to insert the unlock-close when the
> - lock call is interrupted. */
> -
> -static void do_unlock_close(const struct dlm_plock_info *info)
> +static int do_lock_cancel(const struct dlm_plock_info *orig_info)
> {
> struct plock_op *op;
> + int rv;
>
> op = kzalloc(sizeof(*op), GFP_NOFS);
> if (!op)
> - return;
> + return -ENOMEM;
> +
> + op->info = *orig_info;
> + op->info.optype = DLM_PLOCK_OP_CANCEL;
> + op->info.wait = 0;
>
> - op->info.optype = DLM_PLOCK_OP_UNLOCK;
> - op->info.pid = info->pid;
> - op->info.fsid = info->fsid;
> - op->info.number = info->number;
> - op->info.start = 0;
> - op->info.end = OFFSET_MAX;
> - op->info.owner = info->owner;
> -
> - op->info.flags |= DLM_PLOCK_FL_CLOSE;
> send_op(op);
> + wait_event(recv_wq, (op->done != 0));
> +
> + rv = op->info.rv;
> +
> + dlm_release_plock_op(op);
> + return rv;
> }
>
> int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
> @@ -156,7 +152,7 @@ int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
> send_op(op);
>
> if (op->info.wait) {
> - rv = wait_event_killable(recv_wq, (op->done != 0));
> + rv = wait_event_interruptible(recv_wq, (op->done != 0));
It seems that this patch leads to an unnecessary change in behavior
when a fatal signal is received (fatal_signal_pending()): before, the
process would terminate. Now, it will try to cancel the lock, and when
that fails, the process will keep waiting. In case of a fatal signal,
can we skip the cancelling and do what we did before?
> if (rv == -ERESTARTSYS) {
> spin_lock(&ops_lock);
> /* recheck under ops_lock if we got a done != 0,
> @@ -166,17 +162,37 @@ int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
> spin_unlock(&ops_lock);
> goto do_lock_wait;
> }
> - list_del(&op->list);
> spin_unlock(&ops_lock);
>
> + rv = do_lock_cancel(&op->info);
> + switch (rv) {
> + case 0:
> + /* waiter was deleted in user space, answer will never come
> + * remove original request. The original request must be
> + * on recv_list because the answer of do_lock_cancel()
> + * synchronized it.
> + */
> + spin_lock(&ops_lock);
> + list_del(&op->list);
> + spin_unlock(&ops_lock);
> + rv = -EINTR;
> + break;
> + case -ENOENT:
> + /* cancellation wasn't successful but op should be done */
> + fallthrough;
> + default:
> + /* internal error doing cancel we need to wait */
> + goto wait;
> + }
> +
> log_debug(ls, "%s: wait interrupted %x %llx pid %d",
> __func__, ls->ls_global_id,
> (unsigned long long)number, op->info.pid);
> - do_unlock_close(&op->info);
> dlm_release_plock_op(op);
> goto out;
> }
> } else {
> +wait:
> wait_event(recv_wq, (op->done != 0));
> }
>
> diff --git a/include/uapi/linux/dlm_plock.h b/include/uapi/linux/dlm_plock.h
> index 63b6c1fd9169..eb66afcac40e 100644
> --- a/include/uapi/linux/dlm_plock.h
> +++ b/include/uapi/linux/dlm_plock.h
> @@ -22,6 +22,7 @@ enum {
> DLM_PLOCK_OP_LOCK = 1,
> DLM_PLOCK_OP_UNLOCK,
> DLM_PLOCK_OP_GET,
> + DLM_PLOCK_OP_CANCEL,
> };
>
> #define DLM_PLOCK_FL_CLOSE 1
> --
> 2.31.1
>
Thanks,
Andreas
next parent reply other threads:[~2024-03-25 15:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20230718180721.745569-1-aahringo@redhat.com>
[not found] ` <20230718180721.745569-3-aahringo@redhat.com>
2024-03-25 15:08 ` Andreas Gruenbacher [this message]
2024-03-26 0:32 ` [PATCHv3 v6.5-rc2 2/3] fs: dlm: allow to F_SETLKW getting interrupted Alexander Aring
2024-03-26 11:31 ` Andreas Gruenbacher
2024-03-26 13:02 ` Alexander Aring
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