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Re: consequences of XFS_IOC_FSSETXATTR on non-empty file?

To: Samuel Just <sam.just@xxxxxxxxxxx>
Subject: Re: consequences of XFS_IOC_FSSETXATTR on non-empty file?
From: Ilya Dryomov <ilya.dryomov@xxxxxxxxxxx>
Date: Sun, 13 Jul 2014 21:01:13 +0400
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, "ceph-devel@xxxxxxxxxxxxxxx" <ceph-devel@xxxxxxxxxxxxxxx>, Sage Weil <sage@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <CA+4uBUZwuh5t28jU5jfQb3ApdUKx8t88hg6m8CXS+0ztpi6OTw@xxxxxxxxxxxxxx>
References: <CA+4uBUYg+81G2=sj3qXO4GGgA7pyjgVrGDCN+UQ32jnWgSbG5w@xxxxxxxxxxxxxx> <20140713012624.GS4453@dastard> <CA+4uBUZwuh5t28jU5jfQb3ApdUKx8t88hg6m8CXS+0ztpi6OTw@xxxxxxxxxxxxxx>
On Sun, Jul 13, 2014 at 5:48 AM, Samuel Just <sam.just@xxxxxxxxxxx> wrote:
> Actually, on this ubuntu kernel (3.13.0-24-generic), it doesn't seem
> to give an error.  I'll attach my test case for that.  We don't yet
> have a way of reproducing the corruption -- the ext_size change in the
> osd simply seemed like a promising lead.
> -Sam
>
> On Sat, Jul 12, 2014 at 6:26 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
>> On Sat, Jul 12, 2014 at 06:16:54PM -0700, Samuel Just wrote:
>>> Hi,
>>>
>>> We are seeing reports of ceph-osd stores on xfs of files with some
>>> garbage data (possibly misplaced from data elsewhere in the
>>> filesystem).  There was a bug for a while where the ceph-osd process
>>> would set a value for fsx_extsize on a non-empty (possibly sparse)
>>> file using XFS_IOC_FSSETXATTR.  Could that plausibly result in a file
>>> with garbage data?
>>
>> No, setting an extent size on a non-empty file will simply fail
>> with EINVAL.

AFAIR it checks whether or not any extents are actually allocated, not
whether the file is empty or not.  I think if you call fsync() or even
fdatasync() before close(fd), it will fail as expected.

Thanks,

                Ilya

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