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From: "NeilBrown" <neilb@suse.de>
To: "Jeff Layton" <jlayton@kernel.org>
Cc: "Christian Brauner" <brauner@kernel.org>,
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Subject: Re: [PATCH 12/20] filelock: make __locks_delete_block and
 __locks_wake_up_blocks take file_lock_core
In-reply-to: <20240116-flsplit-v1-12-c9d0f4370a5d@kernel.org>
References: <20240116-flsplit-v1-0-c9d0f4370a5d@kernel.org>,
 <20240116-flsplit-v1-12-c9d0f4370a5d@kernel.org>
Date: Wed, 17 Jan 2024 09:23:07 +1100
Message-id: <170544378717.23031.5597414508293858294@noble.neil.brown.name>

On Wed, 17 Jan 2024, Jeff Layton wrote:
> Convert __locks_delete_block and __locks_wake_up_blocks to take a struct
> file_lock_core pointer. Note that to accomodate this, we need to add a
> new file_lock() wrapper to go from file_lock_core to file_lock.

Actually we don't need it.... see below.

>=20
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  fs/locks.c | 43 ++++++++++++++++++++++++++-----------------
>  1 file changed, 26 insertions(+), 17 deletions(-)
>=20
> diff --git a/fs/locks.c b/fs/locks.c
> index eddf4d767d5d..6b8e8820dec9 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -92,6 +92,11 @@ static inline bool IS_LEASE(struct file_lock_core *flc)
> =20
>  #define IS_REMOTELCK(fl)	(fl->fl_core.fl_pid <=3D 0)
> =20
> +struct file_lock *file_lock(struct file_lock_core *flc)
> +{
> +	return container_of(flc, struct file_lock, fl_core);
> +}
> +
>  static bool lease_breaking(struct file_lock *fl)
>  {
>  	return fl->fl_core.fl_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
> @@ -677,31 +682,35 @@ static void locks_delete_global_blocked(struct file_l=
ock_core *waiter)
>   *
>   * Must be called with blocked_lock_lock held.
>   */
> -static void __locks_delete_block(struct file_lock *waiter)
> +static void __locks_delete_block(struct file_lock_core *waiter)
>  {
> -	locks_delete_global_blocked(&waiter->fl_core);
> -	list_del_init(&waiter->fl_core.fl_blocked_member);
> +	locks_delete_global_blocked(waiter);
> +	list_del_init(&waiter->fl_blocked_member);
>  }
> =20
> -static void __locks_wake_up_blocks(struct file_lock *blocker)
> +static void __locks_wake_up_blocks(struct file_lock_core *blocker)
>  {
> -	while (!list_empty(&blocker->fl_core.fl_blocked_requests)) {
> -		struct file_lock *waiter;
> +	while (!list_empty(&blocker->fl_blocked_requests)) {
> +		struct file_lock_core *waiter;
> +		struct file_lock *fl;
> +
> +		waiter =3D list_first_entry(&blocker->fl_blocked_requests,
> +					  struct file_lock_core, fl_blocked_member);
> =20
> -		waiter =3D list_first_entry(&blocker->fl_core.fl_blocked_requests,
> -					  struct file_lock, fl_core.fl_blocked_member);

> +		fl =3D file_lock(waiter);

		fl =3D list_first_entry(&blocker->fl_core.fl_blocked_requests,
				      struct file_lock, fl_core.fl_blocked_member);

                waiter =3D &fl->fl_core;

achieves the same result without needing file_lock().

If you really want to add file_lock() then do so, but you need a better
justification :-)

NeilBrown


>  		__locks_delete_block(waiter);
> -		if (waiter->fl_lmops && waiter->fl_lmops->lm_notify)
> -			waiter->fl_lmops->lm_notify(waiter);
> +		if ((IS_POSIX(waiter) || IS_FLOCK(waiter)) &&
> +		    fl->fl_lmops && fl->fl_lmops->lm_notify)
> +			fl->fl_lmops->lm_notify(fl);
>  		else
> -			wake_up(&waiter->fl_core.fl_wait);
> +			wake_up(&waiter->fl_wait);
> =20
>  		/*
>  		 * The setting of fl_blocker to NULL marks the "done"
>  		 * point in deleting a block. Paired with acquire at the top
>  		 * of locks_delete_block().
>  		 */
> -		smp_store_release(&waiter->fl_core.fl_blocker, NULL);
> +		smp_store_release(&waiter->fl_blocker, NULL);
>  	}
>  }
> =20
> @@ -743,8 +752,8 @@ int locks_delete_block(struct file_lock *waiter)
>  	spin_lock(&blocked_lock_lock);
>  	if (waiter->fl_core.fl_blocker)
>  		status =3D 0;
> -	__locks_wake_up_blocks(waiter);
> -	__locks_delete_block(waiter);
> +	__locks_wake_up_blocks(&waiter->fl_core);
> +	__locks_delete_block(&waiter->fl_core);
> =20
>  	/*
>  	 * The setting of fl_blocker to NULL marks the "done" point in deleting
> @@ -799,7 +808,7 @@ static void __locks_insert_block(struct file_lock *bloc=
ker,
>  	 * waiter, but might not conflict with blocker, or the requests
>  	 * and lock which block it.  So they all need to be woken.
>  	 */
> -	__locks_wake_up_blocks(waiter);
> +	__locks_wake_up_blocks(&waiter->fl_core);
>  }
> =20
>  /* Must be called with flc_lock held. */
> @@ -831,7 +840,7 @@ static void locks_wake_up_blocks(struct file_lock *bloc=
ker)
>  		return;
> =20
>  	spin_lock(&blocked_lock_lock);
> -	__locks_wake_up_blocks(blocker);
> +	__locks_wake_up_blocks(&blocker->fl_core);
>  	spin_unlock(&blocked_lock_lock);
>  }
> =20
> @@ -1186,7 +1195,7 @@ static int posix_lock_inode(struct inode *inode, stru=
ct file_lock *request,
>  			 * Ensure that we don't find any locks blocked on this
>  			 * request during deadlock detection.
>  			 */
> -			__locks_wake_up_blocks(request);
> +			__locks_wake_up_blocks(&request->fl_core);
>  			if (likely(!posix_locks_deadlock(request, fl))) {
>  				error =3D FILE_LOCK_DEFERRED;
>  				__locks_insert_block(fl, request,
>=20
> --=20
> 2.43.0
>=20
>=20