From: Christoph Hellwig <hch@infradead.org>
To: Ritesh Harjani <riteshh@linux.ibm.com>
Cc: Matthew Bobrowski <mbobrowski@mbobrowski.org>,
Christoph Hellwig <hch@infradead.org>,
tytso@mit.edu, jack@suse.cz, adilger.kernel@dilger.ca,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
david@fromorbit.com, darrick.wong@oracle.com
Subject: Re: [PATCH v3 5/6] ext4: introduce direct IO write path using iomap infrastructure
Date: Tue, 17 Sep 2019 02:02:33 -0700 [thread overview]
Message-ID: <20190917090233.GB29487@infradead.org> (raw)
In-Reply-To: <20190917090016.266CB520A1@d06av21.portsmouth.uk.ibm.com>
On Tue, Sep 17, 2019 at 02:30:15PM +0530, Ritesh Harjani wrote:
> So if we have a delayed buffered write to a file,
> in that case we first only update inode->i_size and update
> i_disksize at writeback time
> (i.e. during block allocation).
> In that case when we call for ext4_dio_write_iter
> since offset + len > i_disksize, we call for ext4_update_i_disksize().
>
> Now if writeback for some reason failed. And the system crashes, during the
> DIO writes, after the blocks are allocated. Then during reboot we may have
> an inconsistent inode, since we did not add the inode into the
> orphan list before we updated the inode->i_disksize. And journal replay
> may not succeed.
>
> 1. Can above actually happen? I am still not able to figure out the
> race/inconsistency completely.
> 2. Can you please help explain under what other cases
> it was necessary to call ext4_update_i_disksize() in DIO write paths?
> 3. When will i_disksize be out-of-sync with i_size during DIO writes?
None of the above seems new in this patchset, does it? That being said
I found the early size update odd. XFS updates the on-disk size only
at I/O completion time to deal with various races including the
potential exposure of stale data.
next prev parent reply other threads:[~2019-09-17 9:02 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-12 11:03 [PATCH v3 0/6] ext4: port direct IO to iomap infrastructure Matthew Bobrowski
2019-09-12 11:03 ` [PATCH v3 1/6] ext4: introduce direct IO read path using " Matthew Bobrowski
2019-09-16 12:00 ` Christoph Hellwig
2019-09-16 13:07 ` Matthew Bobrowski
2019-09-12 11:04 ` [PATCH v3 2/6] ext4: move inode extension/truncate code out from ext4_iomap_end() Matthew Bobrowski
2019-09-23 16:21 ` Jan Kara
2019-09-24 9:50 ` Matthew Bobrowski
2019-09-24 13:13 ` Jan Kara
2019-09-12 11:04 ` [PATCH v3 3/6] iomap: split size and error for iomap_dio_rw ->end_io Matthew Bobrowski
2019-09-12 11:04 ` [PATCH v3 4/6] ext4: reorder map.m_flags checks in ext4_iomap_begin() Matthew Bobrowski
2019-09-16 12:05 ` Christoph Hellwig
2019-09-17 12:48 ` Matthew Bobrowski
2019-09-23 15:08 ` Jan Kara
2019-09-24 9:35 ` Matthew Bobrowski
2019-09-12 11:04 ` [PATCH v3 5/6] ext4: introduce direct IO write path using iomap infrastructure Matthew Bobrowski
2019-09-16 4:37 ` Ritesh Harjani
2019-09-16 10:14 ` Matthew Bobrowski
2019-09-16 12:12 ` Christoph Hellwig
2019-09-16 22:37 ` Matthew Bobrowski
2019-09-17 9:00 ` Ritesh Harjani
2019-09-17 9:02 ` Christoph Hellwig [this message]
2019-09-17 10:12 ` Ritesh Harjani
2019-09-17 12:39 ` Matthew Bobrowski
2019-09-24 10:57 ` Jan Kara
2019-09-17 9:06 ` Christoph Hellwig
2019-09-17 11:31 ` Matthew Bobrowski
2019-09-20 13:24 ` Matthew Bobrowski
2019-09-23 21:10 ` Jan Kara
2019-09-24 10:29 ` Matthew Bobrowski
2019-09-24 14:13 ` Jan Kara
2019-09-25 7:14 ` Matthew Bobrowski
2019-09-25 8:40 ` Jan Kara
2019-09-12 11:05 ` [PATCH v3 6/6] ext4: cleanup legacy buffer_head direct IO code Matthew Bobrowski
2019-09-16 12:06 ` Christoph Hellwig
2019-09-16 12:53 ` Matthew Bobrowski
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