Re: [PATCH] checkpoint: don't checkpoint a task with aio requests

[Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>]

Seems sufficient for now - until we get to address AIO.
Added, thanks.

Oren.

Serge E. Hallyn wrote:
> Not sure this is the best way, or entirely foolproof, but at
> least make an attempt to not checkpoint a task which is using
> aio.
> 
> A checkpoint-aware application using aio can have the checkpointer
> signal all tasks to complete aio and wait for the checkpoint to
> complete.
> 
> (Note I still have a queue of the patches at
> http://git.kernel.org/gitweb.cgi?p=linux/kernel/git/sergeh/linux-cr.git;a=shortlog;h=refs/heads/cr-next
> so you should be able to
> 
> git fetch git://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux-cr.git cr-next:serge
> 
> and cherrypick patches from that branch instead
> of wrangling all the patches from mbox...)
> 
> Signed-off-by: Serge E. Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> ---
>  checkpoint/memory.c |    6 ++++++
>  fs/aio.c            |   17 +++++++++++++++++
>  include/linux/aio.h |    2 ++
>  3 files changed, 25 insertions(+), 0 deletions(-)
> 
> diff --git a/checkpoint/memory.c b/checkpoint/memory.c
> index 0108dbe..49e16c5 100644
> --- a/checkpoint/memory.c
> +++ b/checkpoint/memory.c
> @@ -25,6 +25,7 @@
>  #include <linux/swap.h>
>  #include <linux/checkpoint.h>
>  #include <linux/checkpoint_hdr.h>
> +#include <linux/aio.h>
>  
>  /*
>   * page-array chains: each ckpt_pgarr describes a set of <struct page *,vaddr>
> @@ -666,6 +667,11 @@ static int do_checkpoint_mm(struct ckpt_ctx *ctx, struct mm_struct *mm)
>  	struct file *exe_file = NULL;
>  	int ret;
>  
> +	ret = check_for_outstanding_aio(mm);
> +	if (ret < 0) {
> +		ckpt_err(ctx, ret, "(%T)Outstanding aio\n");
> +		return ret;
> +	}
>  	h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_MM);
>  	if (!h)
>  		return -ENOMEM;
> diff --git a/fs/aio.c b/fs/aio.c
> index 02a2c93..7eb764c 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1784,3 +1784,20 @@ SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
>  	asmlinkage_protect(5, ret, ctx_id, min_nr, nr, events, timeout);
>  	return ret;
>  }
> +
> +int check_for_outstanding_aio(struct mm_struct *mm)
> +{
> +	int ret = -EBUSY;
> +	struct kioctx *ctx;
> +	struct hlist_node *n;
> +
> +	rcu_read_lock();
> +	hlist_for_each_entry_rcu(ctx, n, &mm->ioctx_list, list)
> +		if (!ctx->dead)
> +			goto found;
> +	ret = 0;
> +found:
> +	rcu_read_unlock();
> +
> +	return ret;
> +}
> diff --git a/include/linux/aio.h b/include/linux/aio.h
> index aea219d..462f22e 100644
> --- a/include/linux/aio.h
> +++ b/include/linux/aio.h
> @@ -214,6 +214,7 @@ extern void kick_iocb(struct kiocb *iocb);
>  extern int aio_complete(struct kiocb *iocb, long res, long res2);
>  struct mm_struct;
>  extern void exit_aio(struct mm_struct *mm);
> +extern int check_for_outstanding_aio(struct mm_struct *mm);
>  #else
>  static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; }
>  static inline int aio_put_req(struct kiocb *iocb) { return 0; }
> @@ -221,6 +222,7 @@ static inline void kick_iocb(struct kiocb *iocb) { }
>  static inline int aio_complete(struct kiocb *iocb, long res, long res2) { return 0; }
>  struct mm_struct;
>  static inline void exit_aio(struct mm_struct *mm) { }
> +static inline int check_for_outstanding_aio(struct mm_struct *mm) { return 0; }
>  #endif /* CONFIG_AIO */
>  
>  #define io_wait_to_kiocb(wait) container_of(wait, struct kiocb, ki_wait)