From: David Sterba <dsterba@suse.cz>
To: kreijack@inwind.it
Cc: dsterba@suse.cz, util-linux@vger.kernel.org,
linux-btrfs <linux-btrfs@vger.kernel.org>,
Chris Mason <chris.mason@fusionio.com>,
Chris Murphy <lists@colorremedies.com>
Subject: Re: Btrfs: wipe all the superblock [redhat bugzilla 889888]
Date: Tue, 8 Jan 2013 18:14:28 +0100 [thread overview]
Message-ID: <20130108171427.GO20089@twin.jikos.cz> (raw)
In-Reply-To: <50EB11E0.8030403@tiscalinet.it>
On Mon, Jan 07, 2013 at 07:20:16PM +0100, Goffredo Baroncelli wrote:
> On 01/07/2013 05:33 PM, David Sterba wrote:
> > It can have as much as 4 superblock backup copies:
> >
> > Superblock offset 0 is 65536 (0x10000, block=16/0x10)
> > Superblock offset 1 is 67108864 (0x4000000, block=16384/0x4000)
> > Superblock offset 2 is 274877906944 (0x4000000000, block=67108864/0x4000000)
> > Superblock offset 3 is 1125899906842624 (0x4000000000000, block=274877906944/0x4000000000)
> > Superblock offset 4 is 4611686018427387904 (0x4000000000000000, block=1125899906842624/0x4000000000000)
>
> Are you sure ?
>
> Regarding the btrfs-progs suite, I looked at the btrfs_read_dev_super():
> [..]
> for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
> bytenr = btrfs_sb_offset(i);
> ret = pread64(fd, &buf, sizeof(buf), bytenr);
>
> Where BTRFS_SUPER_MIRROR_MAX is 3.
My bad, sorry, I was using the values from an old script that computed
the values with a wrong upper limit.
david
next prev parent reply other threads:[~2013-01-08 17:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-06 18:28 Btrfs: wipe all the superblock [redhat bugzilla 889888] Goffredo Baroncelli
2013-01-07 16:33 ` David Sterba
2013-01-07 18:20 ` Goffredo Baroncelli
2013-01-07 18:24 ` Hugo Mills
2013-01-07 18:33 ` Goffredo Baroncelli
2013-01-08 17:14 ` David Sterba [this message]
2013-01-08 15:48 ` Günter Gersdorf
2013-01-08 20:31 ` Goffredo Baroncelli
2013-01-08 16:43 ` Karel Zak
2013-01-09 17:48 ` Goffredo Baroncelli
2013-01-09 18:10 ` Karel Zak
2013-01-08 18:01 ` Karel Zak
2013-01-08 20:09 ` Goffredo Baroncelli
2013-01-08 20:27 ` Chris Murphy
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