linux-ext4 - Re: [RFC 1/2] iomap: direct-io: Move inode_dio_begin before filemap_write_and_wait

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Message-ID: <20200114090507.GA6466@quack2.suse.cz>
Date:   Tue, 14 Jan 2020 10:05:07 +0100
From:   Jan Kara <jack@...e.cz>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     Ritesh Harjani <riteshh@...ux.ibm.com>, linux-ext4@...r.kernel.org,
        tytso@....edu, jack@...e.cz
Subject: Re: [RFC 1/2] iomap: direct-io: Move inode_dio_begin before
 filemap_write_and_wait_range

On Mon 13-01-20 13:51:59, Darrick J. Wong wrote:
> On Mon, Jan 13, 2020 at 04:34:21PM +0530, Ritesh Harjani wrote:
> > Some filesystems (e.g. ext4) need to know in it's writeback path, that
> > whether DIO is in progress or not. This info may be needed to avoid the
> > stale data exposure race with DIO reads.
> 
> Does XFS have this problem too?
> 
> Admittedly dio read during mmap write is probably not well supported. ;)

Well, XFS always performs buffered writeback using unwritten extents so at
least the immediate problem of stale data exposure ext4 has does not happen
there AFAICT. 

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR