From: David Sterba <dsterba@suse.cz>
To: "Rebraca Dejan (BSOT/PJ-ES1-Bg)" <Dejan.Rebraca@rs.bosch.com>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: FIEMAP ioctl gets "wrong" address for the extent
Date: Thu, 2 Jul 2020 13:43:48 +0200 [thread overview]
Message-ID: <20200702114348.GJ27795@twin.jikos.cz> (raw)
In-Reply-To: <cfd1d2842b4840b99539f00c34dc5701@rs.bosch.com>
On Thu, Jul 02, 2020 at 09:11:20AM +0000, Rebraca Dejan (BSOT/PJ-ES1-Bg) wrote:
> Hi all,
>
> I'm collecting file extents for our application from BtrFs filesystem image.
> I've noticed that for some files a get the "wrong" physical offset for
> start of the extent. I verified it using hexdump of the filesystem
> image: when dump the content starting from the address returned from
> FIEMAP ioctl, I see that the content is absolutely different from the
> content of the file itself. Also, the FIEMAP ioctl reports regular
> extent, it is not inline.
There are 3 address spaces:
- device physical offsets
- filesystem physical offsets
- filesystem logical offsets
What you seem to expect is that device physical and filesystem physical
and the same. This is not true in general in btrfs and fiemap will
return only the filesystem offsets. To get to the device offsets you'd
need to do the reverse mapping.
next prev parent reply other threads:[~2020-07-02 11:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-02 9:11 FIEMAP ioctl gets "wrong" address for the extent Rebraca Dejan (BSOT/PJ-ES1-Bg)
2020-07-02 10:18 ` Qu Wenruo
2020-07-02 11:08 ` Rebraca Dejan (BSOT/PJ-ES1-Bg)
2020-07-02 11:21 ` Qu Wenruo
2020-07-03 7:13 ` Rebraca Dejan (BSOT/PJ-ES1-Bg)
2020-07-06 17:10 ` Omar Sandoval
2020-07-02 11:43 ` David Sterba [this message]
2020-07-07 9:43 ` Anand Jain
2020-07-07 11:38 ` David Sterba
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