From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [RFC] write(2) semantics wrt return values and current position
Date: Wed, 8 Apr 2015 22:20:27 +0100
Message-ID: <20150408212026.GS889@ZenIV.linux.org.uk>
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 <20150408205737.GR889@ZenIV.linux.org.uk>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Trond Myklebust <trond.myklebust@primarydata.com>,
	Christoph Hellwig <hch@infradead.org>,
	Dave Chinner <david@fromorbit.com>,
	Theodore Ts'o <tytso@mit.edu>,
	Miklos Szeredi <miklos@szeredi.hu>,
	Oleg Drokin <oleg.drokin@intel.com>,
	Joseph Qi <joseph.qi@huawei.com>,
	Joel Becker <jlbec@evilplan.org>,
	Mark Fasheh <mfasheh@suse.com>
To: linux-fsdevel@vger.kernel.org
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On Wed, Apr 08, 2015 at 09:57:37PM +0100, Al Viro wrote:
> ... and having looked through old mail, there's _another_ breakage that
> might have inspired that one; this one is mine - "ocfs2 syncs the wrong range".
> It was syncing the wrong range with O_APPEND, all right, but after that
> patch it was syncing the wrong range in _all_ cases.  What it should've
> been doing instead is
>                 ret = filemap_fdatawrite_range(file->f_mapping,
> 					       iocb->ki_pos - written,
>                                                iocb->ki_pos - 1);
> ...
>                         ret = filemap_fdatawait_range(file->f_mapping,
> 						      iocb->ki_pos - written,
>                                                       iocb->ki_pos - 1);
> 
> Joseph, my apologies for missing your mail back in January - you are absolutely
> correct, *ppos (aka iocb->ki_pos) _is_ changed.  Unlike pos, it can be used
> to get the right range reliably (as above; pos, back when it existed,
> hadn't been affected by generic_write_checks() call in what used to be
> ocfs2_file_aio_write()), but the actual calculation had been completely
> wrong.
> 
> If that had contributed to confusion, my deep apologies...

Folks, could you please take a look through vfs.git#for-linus (the last
three commits in there) and see if you are OK with those?