From: Ira Weiny <ira.weiny@intel.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-kernel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Dan Williams <dan.j.williams@intel.com>,
Dave Chinner <david@fromorbit.com>,
Christoph Hellwig <hch@lst.de>,
"Theodore Y. Ts'o" <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC PATCH V2 10/12] fs/xfs: Fix truncate up
Date: Tue, 14 Jan 2020 11:00:57 -0800 [thread overview]
Message-ID: <20200114190057.GB7871@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200114011407.GT8247@magnolia>
On Mon, Jan 13, 2020 at 05:14:07PM -0800, Darrick J. Wong wrote:
> On Mon, Jan 13, 2020 at 04:40:47PM -0800, Ira Weiny wrote:
> > On Mon, Jan 13, 2020 at 02:27:55PM -0800, Darrick J. Wong wrote:
> > > On Fri, Jan 10, 2020 at 11:29:40AM -0800, ira.weiny@intel.com wrote:
> > > > From: Ira Weiny <ira.weiny@intel.com>
> > > >
> > > > When zeroing the end of a file we must account for bytes contained in
> > > > the final page which are past EOF.
> > > >
> > > > Extend the range passed to iomap_zero_range() to reach LLONG_MAX which
> > > > will include all bytes of the final page.
> > > >
> > > > Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> > > > ---
> > > > fs/xfs/xfs_iops.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> > > > index a2f2604c3187..a34b04e8ac9c 100644
> > > > --- a/fs/xfs/xfs_iops.c
> > > > +++ b/fs/xfs/xfs_iops.c
> > > > @@ -910,7 +910,7 @@ xfs_setattr_size(
> > > > */
> > > > if (newsize > oldsize) {
> > > > trace_xfs_zero_eof(ip, oldsize, newsize - oldsize);
> > > > - error = iomap_zero_range(inode, oldsize, newsize - oldsize,
> > > > + error = iomap_zero_range(inode, oldsize, LLONG_MAX - oldsize,
> > >
> > > Huh? Won't this cause the file size to be set to LLONG_MAX?
> >
> > Not as I understand the code.
>
> iomap_zero_range uses the standard iomap_write_{begin,end} functions,
> which means that if you pass it an (offset, length) that extend beyond
> EOF it will change isize to offset+length.
I don't see that but I'll take your word for it... That is unfortunate because
I would have thought that the full page would have been zero'ed by something
already.
I found code in xfs_free_file_space() with this comment:
/*
* If we zeroed right up to EOF and EOF straddles a page boundary we
* must make sure that the post-EOF area is also zeroed because the
* page could be mmap'd and iomap_zero_range doesn't do that for us.
* Writeback of the eof page will do this, albeit clumsily.
*/
But that just calls filemap_write_and_wait_range()... :-/
>
> > But as I said in the cover I am not 100% sure of
> > this fix.
>
> > From what I can tell xfs_ioctl_setattr_dax_invalidate() should invalidate the
> > mappings and the page cache and the traces I have indicate that the DAX mode
> > is not changing or was properly held off.
>
> Hmm, that implies the invalidation didn't work. Can you find a way to
> report the contents of the page cache after the dax mode change
> invalidation fails? I wonder if this is something dorky like rounding
> down such that the EOF page doesn't actually get invalidated?
>
> Hmm, no, xfs_ioctl_setattr_dax_invalidate should be nuking all the
> pages... do you have a quick reproducer?
I thought I did...
What I have done is take this patch:
https://www.spinics.net/lists/fstests/msg13313.html
and put [run_fsx ""] in a loop... (diff below) And without this truncate fix
patch it was failing in about 5 - 10 iterations. But I'm running it right now
and it has gone for 30+... :-(
I am 90% confident that this series works for 100% of the use cases we have. I
think this is an existing bug which I've just managed to find. And again I'm
not comfortable with this patch either. So I'm not trying to argue for it but
I just don't know what could be wrong...
Ira
diff --git a/tests/generic/999 b/tests/generic/999
index 6dd5529dbc65..929c20c6db04 100755
--- a/tests/generic/999
+++ b/tests/generic/999
@@ -274,7 +274,9 @@ function run_fsx {
pid=""
}
-run_fsx ""
+while [ 1 ]; do
+ run_fsx ""
+done
run_fsx "-A"
run_fsx "-Z -r 4096 -w 4096"
next prev parent reply other threads:[~2020-01-14 19:01 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 19:29 [RFC PATCH V2 00/12] Enable per-file/directory DAX operations V2 ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute ira.weiny
2020-01-15 11:37 ` Jan Kara
2020-01-15 17:38 ` Darrick J. Wong
2020-01-15 19:45 ` Ira Weiny
2020-01-15 20:10 ` Dan Williams
2020-01-15 22:38 ` Ira Weiny
2020-01-16 5:39 ` Darrick J. Wong
2020-01-16 6:05 ` Dan Williams
2020-01-16 6:18 ` Darrick J. Wong
2020-01-16 6:25 ` Dan Williams
2020-01-18 9:11 ` Dave Chinner
2020-01-16 17:55 ` Ira Weiny
2020-01-16 18:04 ` Darrick J. Wong
2020-01-16 18:52 ` Ira Weiny
2020-01-16 22:19 ` Darrick J. Wong
2020-01-17 11:58 ` Jan Kara
2020-01-10 19:29 ` [RFC PATCH V2 02/12] fs/xfs: Isolate the physical DAX flag from effective ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 03/12] fs/xfs: Separate functionality of xfs_inode_supports_dax() ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 04/12] fs/xfs: Clean up DAX support check ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 05/12] fs: remove unneeded IS_DAX() check ira.weiny
2020-01-16 9:38 ` Jan Kara
2020-01-16 18:47 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 06/12] fs/xfs: Check if the inode supports DAX under lock ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 07/12] fs: Add locking for a dynamic inode 'mode' ira.weiny
2020-01-13 22:12 ` Darrick J. Wong
2020-01-14 0:20 ` Ira Weiny
2020-01-14 1:03 ` Darrick J. Wong
2020-01-15 19:08 ` Ira Weiny
2020-01-16 5:40 ` Darrick J. Wong
2020-01-16 18:54 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 08/12] fs/xfs: Add lock/unlock mode to xfs ira.weiny
2020-01-13 22:19 ` Darrick J. Wong
2020-01-14 0:35 ` Ira Weiny
2020-01-15 0:57 ` Ira Weiny
2020-01-15 23:52 ` Ira Weiny
2020-01-16 9:24 ` Jan Kara
2020-01-16 19:12 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 09/12] fs: Prevent mode change if file is mmap'ed ira.weiny
2020-01-13 22:22 ` Darrick J. Wong
2020-01-14 0:46 ` Ira Weiny
2020-01-14 1:30 ` Darrick J. Wong
2020-01-14 17:53 ` Ira Weiny
2020-01-15 11:34 ` Jan Kara
2020-01-15 18:24 ` Ira Weiny
2020-01-15 10:21 ` David Laight
2020-01-15 17:53 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 10/12] fs/xfs: Fix truncate up ira.weiny
2020-01-13 22:27 ` Darrick J. Wong
2020-01-14 0:40 ` Ira Weiny
2020-01-14 1:14 ` Darrick J. Wong
2020-01-14 19:00 ` Ira Weiny [this message]
2020-01-14 19:39 ` Ira Weiny
2020-01-10 19:29 ` [RFC PATCH V2 11/12] fs/xfs: Clean up locking in dax invalidate ira.weiny
2020-01-10 19:29 ` [RFC PATCH V2 12/12] fs/xfs: Allow toggle of effective DAX flag ira.weiny
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