linux-kernel - Re: [PATCH] fs: ecryptfs: fixed msync to flush data

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Message-ID: <20130524233139.GA4029@boyd>
Date:	Fri, 24 May 2013 16:31:40 -0700
From:	Tyler Hicks <tyhicks@...onical.com>
To:	Paul Taysom <taysom@...omium.org>
Cc:	Dustin Kirkland <dustin.kirkland@...zang.com>,
	ecryptfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	olofj@...omium.org
Subject: Re: [PATCH] fs: ecryptfs: fixed msync to flush data

On 2013-05-23 14:31:43, Paul Taysom wrote:
> When msync is called on a memory mapped file, that
> data is not flushed to the disk.
> 
> In Linux, msync calls fsync for the file. For ecryptfs,
> fsync just calls the lower level file system's fsync.
> Changed the ecryptfs fsync code to call filemap_write_and_wait
> before calling the lower level fsync.
> 
> Addresses the problem described in http://crbug.com/239536
> 
> Signed-off-by: Paul Taysom <taysom@...omium.org>
> ---

Thanks, Paul! I've pushed this to the eCryptfs next branch:

http://git.kernel.org/cgit/linux/kernel/git/tyhicks/ecryptfs.git/log/?h=next

I also marked it for the stable kernel as affecting 3.6 and newer.

As a side note, we need to make ecryptfs_fsync() more selective about
what gets synced by using filemap_write_and_wait_range() and
vfs_fsync_range(). Since we're already calling vfs_fsync() for the
entire lower file, this patch is good enough for now.

Tyler

>  fs/ecryptfs/file.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
> index 201f0a0..16f509d 100644
> --- a/fs/ecryptfs/file.c
> +++ b/fs/ecryptfs/file.c
> @@ -295,6 +295,7 @@ static int ecryptfs_release(struct inode *inode, struct file *file)
>  static int
>  ecryptfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
>  {
> +	filemap_write_and_wait(file->f_mapping);
>  	return vfs_fsync(ecryptfs_file_to_lower(file), datasync);
>  }
>  
> -- 
> 1.8.2.1
> 

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