[Devel] Re: [PATCH] c/r: fix false negative of test for unlinked files at checkpoint

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at cs.columbia.edu):
> Checkpoint will abort when it detects non-checkpoint-able state. This
> patch fixes a false positive of testing for unlinked files.
> 
> The test for an unlinked file (or directory) is not file system
> agnostic. Commit a3a065e3f13da8a3470ed09c7f38aad256083726 made it
> visible when it changed the behavior of dentry for pipe, sockets and
> anon_inodes (eventfd, timerfd, epoll, signalfd and perf...) to set
> their DCACHE_UNHASHED.
> 
> This is fixed by moving the actual test whether the file is unlinked
> or not to the per filesystem .checkpoint() method, (including the
> default generic_file_checkpoint).
> 
> Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>

Tested-by: Serge Hallyn <serue at us.ibm.com>

> ---
>  checkpoint/files.c |   19 ++++++++++---------
>  1 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/checkpoint/files.c b/checkpoint/files.c
> index d1242f2..267d361 100644
> --- a/checkpoint/files.c
> +++ b/checkpoint/files.c
> @@ -197,14 +197,20 @@ int generic_file_checkpoint(struct ckpt_ctx *ctx, struct file *file)
>  	struct ckpt_hdr_file_generic *h;
>  	int ret;
> 
> -	h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_FILE);
> -	if (!h)
> -		return -ENOMEM;
> -
>  	/*
>  	 * FIXME: when we'll add support for unlinked files/dirs, we'll
>  	 * need to distinguish between unlinked filed and unlinked dirs.
>  	 */
> +	if (d_unlinked(file->f_dentry)) {
> +		ckpt_err(ctx, -EBADF, "%(T)%(P)Unlinked files unsupported\n",
> +			 file);
> +		return -EBADF;
> +	}
> +
> +	h = ckpt_hdr_get_type(ctx, sizeof(*h), CKPT_HDR_FILE);
> +	if (!h)
> +		return -ENOMEM;
> +
>  	h->common.f_type = CKPT_FILE_GENERIC;
> 
>  	ret = checkpoint_file_common(ctx, file, &h->common);
> @@ -231,11 +237,6 @@ int checkpoint_file(struct ckpt_ctx *ctx, void *ptr)
>  			       file, file->f_op);
>  		return -EBADF;
>  	}
> -	if (d_unlinked(file->f_dentry)) {
> -		ckpt_err(ctx, -EBADF, "%(T)%(P)Unlinked files unsupported\n",
> -			 file);
> -		return -EBADF;
> -	}
> 
>  	ret = file->f_op->checkpoint(ctx, file);
>  	if (ret < 0)
> -- 
> 1.6.3.3
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