linux-kernel - Re: [RFC v3][PATCH 8/9] File descriprtors (dump)

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Message-ID: <20080904094740.GY14473@hawkmoon.kerlabs.com>
Date:	Thu, 4 Sep 2008 11:47:40 +0200
From:	Louis Rilling <Louis.Rilling@...labs.com>
To:	Oren Laadan <orenl@...columbia.edu>
Cc:	dave@...ux.vnet.ibm.com, arnd@...db.de, jeremy@...p.org,
	linux-kernel@...r.kernel.org, containers@...ts.linux-foundation.org
Subject: Re: [RFC v3][PATCH 8/9] File descriprtors (dump)

On Thu, Sep 04, 2008 at 04:05:50AM -0400, Oren Laadan wrote:
>
> Dump the files_struct of a task with 'struct cr_hdr_files', followed by
> all open file descriptors. Since FDs can be shared, they are assigned a
> tag and registered in the object hash.
>
> For each open FD there is a 'struct cr_hdr_fd_ent' with the FD, its tag
> and its close-on-exec property. If the FD is to be saved (first time)
> then this is followed by a 'struct cr_hdr_fd_data' with the FD state.
> Then will come the next FD and so on.
>
> This patch only handles basic FDs - regular files, directories and also
> symbolic links.
>

[...]

> diff --git a/checkpoint/ckpt_file.c b/checkpoint/ckpt_file.c
> new file mode 100644
> index 0000000..34df371
> --- /dev/null
> +++ b/checkpoint/ckpt_file.c
> @@ -0,0 +1,224 @@
> +/*
> + *  Checkpoint file descriptors
> + *
> + *  Copyright (C) 2008 Oren Laadan
> + *
> + *  This file is subject to the terms and conditions of the GNU General Public
> + *  License.  See the file COPYING in the main directory of the Linux
> + *  distribution for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +#include <linux/file.h>
> +#include <linux/fdtable.h>
> +#include <linux/ckpt.h>
> +#include <linux/ckpt_hdr.h>
> +
> +#include "ckpt_file.h"
> +
> +#define CR_DEFAULT_FDTABLE  256
> +
> +/**
> + * cr_scan_fds - scan file table and construct array of open fds
> + * @files: files_struct pointer
> + * @fdtable: (output) array of open fds
> + * @return: the number of open fds found
> + *
> + * Allocates the file descriptors array (*fdtable), caller should free
> + */
> +int cr_scan_fds(struct files_struct *files, int **fdtable)
> +{
> +	struct fdtable *fdt;
> +	int *fdlist;
> +	int i, n, max;
> +
> +	max = CR_DEFAULT_FDTABLE;
> +
> + repeat:
> +	n = 0;
> +	fdlist = kmalloc(max * sizeof(*fdlist), GFP_KERNEL);
> +	if (!fdlist)
> +		return -ENOMEM;
> +
> +	spin_lock(&files->file_lock);
> +	fdt = files_fdtable(files);
> +	for (i = 0; i < fdt->max_fds; i++) {
> +		if (fcheck_files(files, i)) {
> +			if (n == max) {
> +				spin_unlock(&files->file_lock);
> +				kfree(fdlist);
> +				max *= 2;
> +				if (max < 0) {	/* overflow ? */
> +					n = -EMFILE;
> +					break;
> +				}
> +				goto repeat;

				fdlist = krealloc(fdlist, max, GFP_KERNEL)?

Sorry, I should have suggested this in my first review.

Louis

> +			}
> +			fdlist[n++] = i;
> +		}
> +	}
> +	spin_unlock(&files->file_lock);
> +
> +	*fdtable = fdlist;
> +	return n;
> +}
> +

-- 
Dr Louis Rilling			Kerlabs
Skype: louis.rilling			Batiment Germanium
Phone: (+33|0) 6 80 89 08 23		80 avenue des Buttes de Coesmes
http://www.kerlabs.com/			35700 Rennes

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