linux-kernel - Re: [PATCH] freezer: Add unsafe versions of freezable_schedule_timeout

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Date:   Thu, 9 Jul 2020 14:32:37 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     zhe.he@...driver.com
Cc:     trond.myklebust@...merspace.com, anna.schumaker@...app.com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        linux-nfs@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] freezer: Add unsafe versions of freezable_schedule_timeout_interruptible
 for NFS

On Mon, Jul 6, 2020 at 11:57 AM <zhe.he@...driver.com> wrote:
>
> From: He Zhe <zhe.he@...driver.com>
>
> commit 0688e64bc600 ("NFS: Allow signal interruption of NFS4ERR_DELAYed operations")
> introduces nfs4_delay_interruptible which also needs an _unsafe version to
> avoid the following call trace for the same reason explained in
> commit 416ad3c9c006 ("freezer: add unsafe versions of freezable helpers for NFS")
>
> CPU: 4 PID: 3968 Comm: rm Tainted: G W 5.8.0-rc4 #1
> Hardware name: Marvell OcteonTX CN96XX board (DT)
> Call trace:
> dump_backtrace+0x0/0x1dc
> show_stack+0x20/0x30
> dump_stack+0xdc/0x150
> debug_check_no_locks_held+0x98/0xa0
> nfs4_delay_interruptible+0xd8/0x120
> nfs4_handle_exception+0x130/0x170
> nfs4_proc_rmdir+0x8c/0x220
> nfs_rmdir+0xa4/0x360
> vfs_rmdir.part.0+0x6c/0x1b0
> do_rmdir+0x18c/0x210
> __arm64_sys_unlinkat+0x64/0x7c
> el0_svc_common.constprop.0+0x7c/0x110
> do_el0_svc+0x24/0xa0
> el0_sync_handler+0x13c/0x1b8
> el0_sync+0x158/0x180
>
> Signed-off-by: He Zhe <zhe.he@...driver.com>

Applied as 5.9 material with some edits in the subject, thanks!

> ---
>  fs/nfs/nfs4proc.c       |  2 +-
>  include/linux/freezer.h | 14 ++++++++++++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index e32717fd1169..15ecfa474e37 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -414,7 +414,7 @@ static int nfs4_delay_interruptible(long *timeout)
>  {
>         might_sleep();
>
> -       freezable_schedule_timeout_interruptible(nfs4_update_delay(timeout));
> +       freezable_schedule_timeout_interruptible_unsafe(nfs4_update_delay(timeout));
>         if (!signal_pending(current))
>                 return 0;
>         return __fatal_signal_pending(current) ? -EINTR :-ERESTARTSYS;
> diff --git a/include/linux/freezer.h b/include/linux/freezer.h
> index 21f5aa0b217f..27828145ca09 100644
> --- a/include/linux/freezer.h
> +++ b/include/linux/freezer.h
> @@ -207,6 +207,17 @@ static inline long freezable_schedule_timeout_interruptible(long timeout)
>         return __retval;
>  }
>
> +/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
> +static inline long freezable_schedule_timeout_interruptible_unsafe(long timeout)
> +{
> +       long __retval;
> +
> +       freezer_do_not_count();
> +       __retval = schedule_timeout_interruptible(timeout);
> +       freezer_count_unsafe();
> +       return __retval;
> +}
> +
>  /* Like schedule_timeout_killable(), but should not block the freezer. */
>  static inline long freezable_schedule_timeout_killable(long timeout)
>  {
> @@ -285,6 +296,9 @@ static inline void set_freezable(void) {}
>  #define freezable_schedule_timeout_interruptible(timeout)              \
>         schedule_timeout_interruptible(timeout)
>
> +#define freezable_schedule_timeout_interruptible_unsafe(timeout)       \
> +       schedule_timeout_interruptible(timeout)
> +
>  #define freezable_schedule_timeout_killable(timeout)                   \
>         schedule_timeout_killable(timeout)
>
> --
> 2.17.1
>