From: Jeff Moyer <jmoyer@redhat.com>
To: "Wilcox\, Matthew R" <matthew.r.wilcox@intel.com>
Cc: "linda.knippers\@hp.com" <linda.knippers@hp.com>,
"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-fsdevel\@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: regression introduced by "block: Add support for DAX reads/writes to block devices"
Date: Fri, 07 Aug 2015 16:41:10 -0400 [thread overview]
Message-ID: <x49bneiygpl.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <100D68C7BA14664A8938383216E40DE0409144D9@FMSMSX114.amr.corp.intel.com> (Matthew R. Wilcox's message of "Fri, 7 Aug 2015 18:11:14 +0000")
"Wilcox, Matthew R" <matthew.r.wilcox@intel.com> writes:
> So ... what you're doing here is if somebody requests the last 512
> bytes, you're asking for the last page. That's going to work as long
> as the partition is a multiple of PAGE_SIZE, but not if the partition
> happens to be misaligned. It's an improvement, although I'd be
> tempted to do this as:
>
> if (pos == max) {
> unsigned blkbits = inode->i_blkbits;
> - sector_t block = pos >> blkbits;
> + long page = pos >> PAGE_SHIFT;
> + sector_t block = page << (PAGE_SHIFT - blkbits);
> unsigned first = pos - (block << blkbits);
> long size;
Yeah, that's easier to read.
> We need to cope with the case where the end of a partition isn't on a
> page boundary though.
Well, that's usually done by falling back to buffered I/O. I gave that
a try and panicked the box. :) I'll keep looking into it, but probably
won't have another patch until next week.
Cheers,
Jeff
next prev parent reply other threads:[~2015-08-07 20:41 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-05 20:19 regression introduced by "block: Add support for DAX reads/writes to block devices" Jeff Moyer
2015-08-05 22:01 ` Dave Chinner
2015-08-06 1:42 ` Linda Knippers
2015-08-06 3:24 ` Dave Chinner
2015-08-06 7:52 ` Boaz Harrosh
2015-08-06 20:34 ` Dave Chinner
2015-08-09 8:52 ` Boaz Harrosh
2015-08-10 16:32 ` Linda Knippers
2015-08-10 21:27 ` Dave Chinner
2015-08-10 23:04 ` Linda Knippers
2015-08-06 14:21 ` Wilcox, Matthew R
2015-08-06 15:33 ` Jeff Moyer
2015-08-06 15:51 ` Wilcox, Matthew R
2015-08-06 21:30 ` Jeff Moyer
2015-08-07 18:11 ` Wilcox, Matthew R
2015-08-07 20:41 ` Jeff Moyer [this message]
2015-08-10 7:42 ` Boaz Harrosh
2015-08-12 21:11 ` Jeff Moyer
2015-08-13 5:32 ` Boaz Harrosh
2015-08-13 14:00 ` Jeff Moyer
2015-08-13 16:42 ` Linda Knippers
2015-08-13 17:14 ` Jeff Moyer
2015-08-13 17:52 ` Linda Knippers
2015-08-13 18:19 ` Jeff Moyer
2015-08-13 19:32 ` Wilcox, Matthew R
2015-08-14 16:28 ` Dan Williams
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