linux-kernel - Re: [PATCH 2/8] swap: lock i_mutex for swap_writepage direct

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20141217080610.GA20335@infradead.org>
Date:	Wed, 17 Dec 2014 00:06:10 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	Omar Sandoval <osandov@...ndov.com>
Cc:	Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	David Sterba <dsterba@...e.cz>, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] swap: lock i_mutex for swap_writepage direct_IO

On Tue, Dec 16, 2014 at 12:56:24AM -0800, Omar Sandoval wrote:
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1728,6 +1728,9 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
>         }
>  
>         if (mapping->a_ops->swap_activate) {
> +               if (!mapping->a_ops->direct_IO)
> +                       return -EINVAL;
> +               swap_file->f_flags |= O_DIRECT;
>                 ret = mapping->a_ops->swap_activate(sis, swap_file, span);
>                 if (!ret) {
>                         sis->flags |= SWP_FILE;

This needs to hold swap_file->f_lock, but otherwise looks good.

> This seems to be more or less equivalent to doing a fcntl(F_SETFL) to
> add the O_DIRECT flag to swap_file (which is a struct file *). Swapoff
> calls filp_close on swap_file, so I don't see why it's necessary to
> clear the flag.

filp_lose doesn't nessecarily destroy the file structure, there might be
other reference to it, e.g. from dup() or descriptor passing.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/