From: Matthew Wilcox <willy@linux.intel.com>
To: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>,
Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
linux-ext4@vger.kernel.org
Subject: Re: [PATCH] ext4: Return the length of a hole from get_block
Date: Mon, 13 Jul 2015 11:26:15 -0400 [thread overview]
Message-ID: <20150713152615.GH13681@linux.intel.com> (raw)
In-Reply-To: <20150713151610.GC17075@quack.suse.cz>
On Mon, Jul 13, 2015 at 05:16:10PM +0200, Jan Kara wrote:
> On Fri 03-07-15 11:15:11, Matthew Wilcox wrote:
> > From: Matthew Wilcox <willy@linux.intel.com>
> >
> > Currently, if ext4's get_block encounters a hole, it does not modify the
> > buffer_head. That's fine for many callers, but for DAX, it's useful to
> > know how large the hole is. XFS already returns the length of the hole,
> > so this improvement should not confuse any callers.
> >
> > Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
>
> So I'm somewhat wondering: What is the reason of BH_Uptodate flag being
> set? I can see the XFS sets it in some cases as well but the use of the
> flag isn't really clear to me...
No clue. I'm just following the documentation in buffer.c:
* NOTE! All mapped/uptodate combinations are valid:
*
* Mapped Uptodate Meaning
*
* No No "unknown" - must do get_block()
* No Yes "hole" - zero-filled
* Yes No "allocated" - allocated on disk, not read in
* Yes Yes "valid" - allocated and up-to-date in memory.
next prev parent reply other threads:[~2015-07-13 15:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-03 15:15 [PATCH] ext4: Return the length of a hole from get_block Matthew Wilcox
2015-07-13 15:16 ` Jan Kara
2015-07-13 15:26 ` Matthew Wilcox [this message]
2015-07-14 9:02 ` Jan Kara
2015-07-14 13:48 ` Matthew Wilcox
2015-07-14 22:24 ` Dave Chinner
2015-07-15 9:59 ` Jan Kara
2015-07-16 1:46 ` Dave Chinner
2015-07-16 7:08 ` Jan Kara
2015-07-17 22:11 ` Dave Chinner
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=20150713152615.GH13681@linux.intel.com \
--to=willy@linux.intel.com \
--cc=adilger.kernel@dilger.ca \
--cc=jack@suse.cz \
--cc=linux-ext4@vger.kernel.org \
--cc=matthew.r.wilcox@intel.com \
--cc=tytso@mit.edu \
/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).