Re: [PATCH 11/17][cr][v4]: Add ->fl_type_prev field.

[Oren Laadan <orenl@cs.columbia.edu>]

On 08/16/2010 03:43 PM, Sukadev Bhattiprolu wrote:
> In preparation for checkpoint/restart of file leases, add ->fl_type_prev
> field to 'struct file_lock'. This field is needed to correctly restore
> file leases in case of recursive checkpoint/restart of an in-progress
> lease.

Nit: since it isn't obvious why fl_type_prev field exists,
maybe add this comment also inside fs.h  (so that future
readers won't need to look it up in the git history) ?

Oren.

> 
> This ->fl_type_prev is only initialized in this patch. It will actually
> be used when restoring file leases after a checkpoint.
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
> ---
>  fs/locks.c         |   10 ++++++++++
>  include/linux/fs.h |    1 +
>  2 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 0bd5af7..9a00876 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -184,6 +184,7 @@ void locks_init_lock(struct file_lock *fl)
>  	fl->fl_file = NULL;
>  	fl->fl_flags = 0;
>  	fl->fl_type = 0;
> +	fl->fl_type_prev = 0;
>  	fl->fl_start = fl->fl_end = 0;
>  	fl->fl_break_time = 0UL;
>  	fl->fl_ops = NULL;
> @@ -227,6 +228,7 @@ void __locks_copy_lock(struct file_lock *new, const struct file_lock *fl)
>  	new->fl_file = NULL;
>  	new->fl_flags = fl->fl_flags;
>  	new->fl_type = fl->fl_type;
> +	new->fl_type_prev = fl->fl_type_prev;
>  	new->fl_start = fl->fl_start;
>  	new->fl_end = fl->fl_end;
>  	new->fl_break_time = 0UL;
> @@ -293,6 +295,13 @@ static int assign_type(struct file_lock *fl, int type)
>  	case F_WRLCK:
>  	case F_UNLCK:
>  		fl->fl_type = type;
> +		/*
> +		 * Clear ->fl_type_prev since this is a new lease type.
> +		 * break_lease() will use this cleared state to know
> +		 * if it must save the lease-type in case of checkpoint/
> +		 * restart.
> +		 */
> +		fl->fl_type_prev = 0;
>  		break;
>  	default:
>  		return -EINVAL;
> @@ -1222,6 +1231,7 @@ int __break_lease(struct inode *inode, unsigned int mode)
>  
>  	for (fl = flock; fl && IS_LEASE(fl); fl = fl->fl_next) {
>  		if (fl->fl_type != future) {
> +			fl->fl_type_prev = fl->fl_type;
>  			fl->fl_type = future;
>  			fl->fl_break_time = break_time;
>  			/* lease must have lmops break callback */
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 49d4eeb..299cc09 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1066,6 +1066,7 @@ struct file_lock {
>  	fl_owner_t fl_owner;
>  	unsigned char fl_flags;
>  	unsigned char fl_type;
> +	unsigned char fl_type_prev;
>  	unsigned int fl_pid;
>  	struct pid *fl_nspid;
>  	wait_queue_head_t fl_wait;