On Thu, Feb 11, 2010 at 05:15:03PM +0530, Nikanth Karthikesan wrote:
> On Thursday 11 February 2010 16:45:24 Ankit Jain wrote:
> > > +static int __init readahead(char *str)
> > > +{
> > > + if (!str)
> > > + return -EINVAL;
> > > + vm_max_readahead_kb = memparse(str, &str) / 1024ULL;
> >
> > Just wondering, shouldn't you check whether the str had a valid value
> > [memparse (str, &next); next > str ..] and if it didn't, then use the
> > DEFAULT_VM_MAX_READAHEAD ? Otherwise, incase of a invalid
> > value, the readahead value will become zero.
> >
>
> Thanks for the review. Here is the fixed patch that checks whether all of the
> parameters value is consumed.
>
> Thanks
> Nikanth
>
> From: Nikanth Karthikesan <knikanth@xxxxxxx>
>
> Add new kernel parameter "readahead", which would be used instead of the
> value of VM_MAX_READAHEAD. If the parameter is not specified, the default
> of 128kb would be used.
>
> Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>
>
> ---
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 736d456..354e6f1 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2148,6 +2148,8 @@ and is between 256 and 4096 characters. It is defined in the file
> Format: <reboot_mode>[,<reboot_mode2>[,...]]
> See arch/*/kernel/reboot.c or arch/*/kernel/process.c
>
> + readahead= Default readahead value for block devices.
> +
I think the description should define the units (kb) and valid value
ranges e.g. page size to something not excessive - say 65536kb. The
above description is, IMO, useless without refering to the source to
find out this information....
[snip]
> @@ -249,6 +250,24 @@ static int __init loglevel(char *str)
>
> early_param("loglevel", loglevel);
>
> +static int __init readahead(char *str)
> +{
> + unsigned long readahead_kb;
> +
> + if (!str)
> + return -EINVAL;
> + readahead_kb = memparse(str, &str) / 1024ULL;
> + if (*str != '\0')
> + return -EINVAL;
And readahead_kb needs to be validated against the range of
valid values here.
> +
> + vm_max_readahead_kb = readahead_kb;
> + default_backing_dev_info.ra_pages = vm_max_readahead_kb
> + * 1024 / PAGE_CACHE_SIZE;
> + return 0;
> +}
> +
> +early_param("readahead", readahead);
> +
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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