From: Andrei Borzenkov <arvidjaar@gmail.com>
To: Chris Murphy <lists@colorremedies.com>,
Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: Does GRUB btrfs support log tree?
Date: Sat, 26 Oct 2019 10:12:02 +0300 [thread overview]
Message-ID: <d1874d17-700a-d78d-34be-eec0544c9de2@gmail.com> (raw)
In-Reply-To: <CAJCQCtS1v7waFA=ERafSCSCHmPJVytdFZkJLqNTC3U3Gw3Y7tA@mail.gmail.com>
25.10.2019 12:47, Chris Murphy пишет:
> I see references to root and chunk trees, but not the log tree.
>
> If boot related files: kernel, initramfs, bootloader configuration
> files, are stored on Btrfs; and if they are changed in such a way as
> to rely on the log tree; and then there's a crash; what's the worse
> case scenario effect?
>
> At first glance, if the bootloader doesn't support log tree, it would
> have a stale view of the file system.
Yes, happened to me several times on ext4.
> Since log tree writes means a
> full file system update hasn't happened, the old file system state
> hasn't been dereferenced, so even in an SSD + discard case, the system
> should still be bootable. And at that point Btrfs kernel code does log
> replay, and catches the system up, and the next update will boot the
> new state.
>
> Correct?
>
Yes. If we speak about grub here, it actually tries very hard to ensure
writes has hit disk (it fsyncs files as it writes them and it flushes
raw devices). But I guess that fsync on btrfs just goes into log and
does not force transaction. Is it possible to force transaction on btrfs
from user space?
next prev parent reply other threads:[~2019-10-26 7:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 9:47 Does GRUB btrfs support log tree? Chris Murphy
2019-10-25 9:50 ` Chris Murphy
2019-10-26 7:12 ` Andrei Borzenkov [this message]
2019-10-27 20:05 ` Chris Murphy
2019-11-04 19:34 ` David Sterba
2019-11-11 19:37 ` Chris Murphy
2019-11-12 20:04 ` Goffredo Baroncelli
2019-11-13 17:00 ` Chris Murphy
2019-11-13 18:54 ` Goffredo Baroncelli
2019-11-13 21:50 ` Chris Murphy
2019-11-14 8:18 ` Andrei Borzenkov
2019-11-17 23:24 ` Chris Murphy
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