Re: o_sync in vfat driver

[Andrew Morton <akpm@osdl.org>]

Chris Mason <mason@suse.com> wrote:
>
> On Monday 27 February 2006 18:12, Andrew Morton wrote:
> 
> > We don't know that the same number of same-sized write()s were happening in
> > each case.
> >
> > There's been some talk about implementing fsync()-on-file-close for this
> > problem, and some protopatches.  But nothing final yet.
> 
> Here's the patch I'm using in -suse right now.  What I want to do is make a 
> much more generic -o flush, but it'll still need a few bits in individual 
> filesystem to kick off metadata writes quickly.
> 
> The basic goal behind the code is to trigger writes without waiting for both
> data and metadata.  If the user is watching the memory stick, when the 
> little light stops flashing all the data and metadata will be on disk.
> 
> It also generally throttles userland a little during file release.  This 
> could be changed to throttle for each page dirtied, but most users I 
> asked liked the current setup better.
> 
> ...
>
> +static int
> +fat_file_release(struct inode *inode, struct file *filp)

On a single line, please.

> +	if (MSDOS_SB(inode->i_sb)->options.flush) {

Did you consider making `-o flush' a generic mount option rather than
msdos-only?

I guess there isn't a lot of demand for this for other filesystems, and
having an ignored option like this is a bit misleading...

> +void
> +writeback_inode(struct inode *inode)
> +{
> +
> +	struct address_space *mapping = inode->i_mapping;
> +	struct writeback_control wbc = {
> +		.sync_mode = WB_SYNC_NONE,
> +		.nr_to_write = 0,
> +	};
> +	sync_inode(inode, &wbc);
> +	filemap_fdatawrite(mapping);

I think that filemap_fdatawrite() will be a no-op?