linux-ext4 - Re: [PATCH 1/5] ext4: introduce direct IO read code path using iomap infrastructure

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Message-ID: <20190813104547.GA3911@poseidon.bobrowski.net>
Date:   Tue, 13 Aug 2019 20:45:48 +1000
From:   Matthew Bobrowski <mbobrowski@...browski.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Christoph Hellwig <hch@...radead.org>, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, jack@...e.cz, tytso@....edu,
        riteshh@...ux.ibm.com
Subject: Re: [PATCH 1/5] ext4: introduce direct IO read code path using iomap
 infrastructure

On Mon, Aug 12, 2019 at 01:17:35PM -0700, Matthew Wilcox wrote:
> On Mon, Aug 12, 2019 at 10:18:35AM -0700, Christoph Hellwig wrote:
> > >  		return -EIO;
> > >  
> > >  	if (!iov_iter_count(to))
> > >  		return 0; /* skip atime */
> > >  
> > >  #ifdef CONFIG_FS_DAX
> > > -	if (IS_DAX(file_inode(iocb->ki_filp)))
> > > +	if (IS_DAX(inode))
> > >  		return ext4_dax_read_iter(iocb, to);
> > >  #endif
> > 
> > Same here.
> 
> It doesn't even need IS_ENABLED.
> 
> include/linux/fs.h:#define IS_DAX(inode)                ((inode)->i_flags & S_DAX)
> 
> #ifdef CONFIG_FS_DAX
> #define S_DAX           8192    /* Direct Access, avoiding the page cache */
> #else
> #define S_DAX           0       /* Make all the DAX code disappear */
> #endif

Ah, clever - I like it! I actually didn't see this and thank you for
highlighting. I guess I will be dropping the CONFIG_FS_DAX statement
here...

--M