Louis Rilling wrote:
> 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.
That's a good point; I did it this way to be paranoid, even though the
the checkpointee is supposed to be frozen (e.g., if the checkpointee is
forcefully killed by, say, OOM, and it's fdt->max_fds goes to zero. But
now I notice that check_files() already tests for this. I'm not sure it
makes the code simpler, but I'll fix that.
Oren.
>
> Louis
>
>> + }
>> + fdlist[n++] = i;
>> + }
>> + }
>> + spin_unlock(&files->file_lock);
>> +
>> + *fdtable = fdlist;
>> + return n;
>> +}
>> +
>
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