linux-kernel - Re: [PATCH 23/23] vfs: Teach readahead to use the file_hotplug

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Date:	Wed, 03 Jun 2009 16:25:29 -0700
From:	Badari Pulavarty <pbadari@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, Hugh Dickins <hugh@...itas.com>,
	Tejun Heo <tj@...nel.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	"Eric W. Biederman" <ebiederm@...well.aristanetworks.com>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 23/23] vfs: Teach readahead to use the file_hotplug_lock

On Mon, 2009-06-01 at 14:50 -0700, Eric W. Biederman wrote:
> From: Eric W. Biederman <ebiederm@...well.aristanetworks.com>
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>
> ---
>  mm/filemap.c |   25 ++++++++++++++++---------
>  1 files changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 379ff0b..5016aa5 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1402,16 +1402,23 @@ SYSCALL_DEFINE(readahead)(int fd, loff_t offset, size_t count)
>  
>  	ret = -EBADF;
>  	file = fget(fd);
> -	if (file) {
> -		if (file->f_mode & FMODE_READ) {
> -			struct address_space *mapping = file->f_mapping;
> -			pgoff_t start = offset >> PAGE_CACHE_SHIFT;
> -			pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
> -			unsigned long len = end - start + 1;
> -			ret = do_readahead(mapping, file, start, len);
> -		}
> -		fput(file);
> +	if (!file)
> +		goto out;
> +
> +	if (!(file->f_mode & FMODE_READ))
> +		goto out_fput;
> +

To be consistent with others, don't you want to do
	  ret = -EIO;
here ?
> +	if (file_hotplug_read_trylock(file)) {
> +		struct address_space *mapping = file->f_mapping;
> +		pgoff_t start = offset >> PAGE_CACHE_SHIFT;
> +		pgoff_t end = (offset + count - 1) >> PAGE_CACHE_SHIFT;
> +		unsigned long len = end - start + 1;
> +		ret = do_readahead(mapping, file, start, len);
> +		file_hotplug_read_unlock(file);
>  	}
> +out_fput:
> +	fput(file);
> +out:
>  	return ret;
>  }
>  #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS

Thanks,
Badari

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