linux-kernel - Re: [PATCH] fcntl: Add the F

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Date:	Thu, 25 Nov 2010 11:08:45 -0700
From:	Andreas Dilger <adilger.kernel@...ger.ca>
To:	Morten Hustveit <mortehu@...g.uio.no>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fcntl: Add the F_READAHEAD command

On 2010-11-25, at 02:54, Morten Hustveit wrote:
> +static int f_readahead(struct file *filp, unsigned long arg)
> +{
> +	if (arg) {
> +		filp->f_ra.ra_pages = (arg + PAGE_SIZE - 1) >> PAGE_SHIFT;

Functionality itself is fine, but it would be clearer if you used a better variable name than "arg" here.  Something like "readahead_bytes" or similar would make it immediately clear what the parameter is.

> +		spin_lock(&filp->f_lock);
> +		filp->f_mode &= ~FMODE_RANDOM;
> +		spin_unlock(&filp->f_lock);
> +	} else {
> +		spin_lock(&filp->f_lock);
> +		filp->f_mode |= FMODE_RANDOM;
> +		spin_unlock(&filp->f_lock);
> +	}
> +
> +	return 0;
> +}
> +
> static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
> 		struct file *filp)
> {
> @@ -420,6 +445,9 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
> 	case F_GETPIPE_SZ:
> 		err = pipe_fcntl(filp, cmd, arg);
> 		break;
> +	case F_READAHEAD:
> +		err = f_readahead(filp, arg);
> +		break;
> 	default:
> 		break;
> 	}
> diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
> index afc00af..69d8e4d 100644
> --- a/include/linux/fcntl.h
> +++ b/include/linux/fcntl.h
> @@ -28,6 +28,11 @@
> #define F_GETPIPE_SZ	(F_LINUX_SPECIFIC_BASE + 8)
> 
> /*
> + * Set read-ahead buffer size
> + */
> +#define F_READAHEAD	(F_LINUX_SPECIFIC_BASE + 9)
> +
> +/*
> * Types of directory notifications that may be requested.
> */
> #define DN_ACCESS	0x00000001	/* File accessed */
> --
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Cheers, Andreas





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