From: Dave Chinner <david@fromorbit.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org,
Dan Williams <dan.j.williams@intel.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [PATCH 6/6] dax: Avoid page invalidation races and unnecessary radix tree traversals
Date: Tue, 4 Oct 2016 10:40:30 +1100 [thread overview]
Message-ID: <20161003234030.GV9806@dastard> (raw)
In-Reply-To: <20161003145802.GD14183@quack2.suse.cz>
On Mon, Oct 03, 2016 at 04:58:02PM +0200, Jan Kara wrote:
> On Wed 28-09-16 10:20:34, Dave Chinner wrote:
> > On Tue, Sep 27, 2016 at 06:43:35PM +0200, Jan Kara wrote:
> > > @@ -1410,6 +1422,17 @@ iomap_dax_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
> > > if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED))
> > > return -EIO;
> > >
> > > + /*
> > > + * Write can allocate block for an area which has a hole page mapped
> > > + * into page tables. We have to tear down these mappings so that data
> > > + * written by write(2) is visible in mmap.
> > > + */
> > > + if (iomap->flags & IOMAP_F_NEW && inode->i_mapping->nrpages) {
> >
> > gcc should be throwing warnings about that:
> >
> > if ((iomap->flags & IOMAP_F_NEW) && inode->i_mapping->nrpages) {
>
> Actually the bitwise '&' takes precedense over the logical '&&' so the
> evaluation order ends up being correct.
Yes, I know that.
However, my concern is that such expressions don't indicate the
/intent/ of the author and so it can be difficult when reading the
code to determine if the logic is correct or whether it is a typo
and is wrong. In many cases, & and && will function identically for
the tested cases, so neither cursory review or testing would catch
something like this being wrong.
> But I agree it's better to be
> explicit with parenthesis here. Fixed.
Yup, a little bit of "documentation" goes a long way :P
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2016-10-03 23:40 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 16:43 [PATCH 0/6] dax: Page invalidation fixes Jan Kara
2016-09-27 16:43 ` [PATCH 1/6] dax: Do not warn about BH_New buffers Jan Kara
2016-09-30 8:53 ` Christoph Hellwig
2016-09-27 16:43 ` [PATCH 2/6] ext2: Return BH_New buffers for zeroed blocks Jan Kara
2016-09-30 8:53 ` Christoph Hellwig
2016-09-27 16:43 ` [PATCH 3/6] ext4: Remove clearing of BH_New bit " Jan Kara
2016-09-30 8:53 ` Christoph Hellwig
2016-09-27 16:43 ` [PATCH 4/6] xfs: Set BH_New for allocated DAX blocks in __xfs_get_blocks() Jan Kara
2016-09-27 17:01 ` Christoph Hellwig
2016-09-27 17:17 ` Jan Kara
2016-09-28 0:22 ` Dave Chinner
2016-10-03 14:44 ` Jan Kara
2016-09-28 2:13 ` Christoph Hellwig
2016-10-03 14:42 ` Jan Kara
2016-10-03 16:39 ` Christoph Hellwig
2016-09-27 16:43 ` [PATCH 5/6] mm: Invalidate DAX radix tree entries only if appropriate Jan Kara
2016-09-28 0:18 ` Dave Chinner
2016-10-03 14:52 ` Jan Kara
2016-09-30 8:57 ` Christoph Hellwig
2016-10-03 12:56 ` Jan Kara
2016-09-27 16:43 ` [PATCH 6/6] dax: Avoid page invalidation races and unnecessary radix tree traversals Jan Kara
2016-09-28 0:20 ` Dave Chinner
2016-10-03 14:58 ` Jan Kara
2016-10-03 23:40 ` Dave Chinner [this message]
2016-09-30 8:55 ` Christoph Hellwig
2016-10-03 15:02 ` Jan Kara
2016-09-30 8:59 ` [PATCH 0/6] dax: Page invalidation fixes Christoph Hellwig
2016-10-03 13:01 ` Jan Kara
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161003234030.GV9806@dastard \
--to=david@fromorbit.com \
--cc=dan.j.williams@intel.com \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-nvdimm@lists.01.org \
--cc=ross.zwisler@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).