[Toybox] [PATCH] fallocate

[hhm]

thanks!!!

Awesome! By the way I am guessing you meant -n instead of -k (because
I could only find man pages for -n)

This is a nice utility (basically bypasses file system management -
very useful for swap, loop block devices, and the like). It is an
awesome thing to have!

Thanks again!


On 8/9/13, Felix Janda <felix.janda at posteo.de> wrote:
> hhm wrote:
>> Here is a request for a new toy:
>>
>> fallocate
>>
>> This would be similar to the "readlink" toy; a wrapper for a syscall.
>>
>> A similar effect can be procured by making a sparse file using
>> "truncate" or a zeroed file by using "dd" and /dev/zero as input
>> ("if="). However, "truncate" does something different (sparse file
>> instead of real file), and "dd" takes much longer, since it writes the
>> file in addition to allocating it.
>>
>> See <https://wiki.archlinux.org/index.php/Swap#Swap_file_creation> for
>> an example.
>>
>> It is likely simple to implement this, at least the basic (no optional
>> args; only mandatory filename/size params) functionality.
>>
>> Someone more familiar with toybox source and C can likely do a good
>> job for this :-).
>
> Below is a patch to add a simple version like you proposed. It would
> be very simple to add the -o and the -k options (if there is need).
> I'm not sure about the correct permissions of the possibly newly
> created file.
>
> Felix
>
> # HG changeset patch
> # User Felix Janda <felix.janda at posteo.de>
> # Date 1376073962 -7200
> # Node ID 4837af10cc3690c7c56d9ab7c02db1c01f44bd31
> # Parent  910f35ff76be14699fc65299b0f08dee4c0c5440
> New toy: fallocate
>
> diff -r 910f35ff76be -r 4837af10cc36 toys/other/fallocate.c
> --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
> +++ b/toys/other/fallocate.c	Fri Aug 09 20:46:02 2013 +0200
> @@ -0,0 +1,30 @@
> +/* fallocate.c - Preallocate space to a file
> + *
> + * Copyright 2013 Felix Janda <felix.janda at posteo.de>
> + *
> + * No standard
> +
> +USE_FALLOCATE(NEWTOY(fallocate, ">1l#|", TOYFLAG_USR|TOYFLAG_BIN))
> +
> +config FALLOCATE
> +  bool "fallocate"
> +  default n
> +  help
> +    usage: fallocate [-l size] file
> +
> +    Tell the filesystem to allocate space for a file.
> +*/
> +
> +#define FOR_fallocate
> +#include "toys.h"
> +
> +GLOBALS(
> +  long size;
> +)
> +
> +void fallocate_main(void)
> +{
> +  int fd = xcreate(*toys.optargs, O_RDWR | O_CREAT, 0644);
> +  if (posix_fallocate(fd, 0, TT.size)) error_exit("Not enough space");
> +  if (CFG_TOYBOX_FREE) close(fd);
> +}
>

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