Btrfs devel - Jul 2011 - will mkfs.btrfs do an initial pre-discard for SSDs like mke2fs does for Ext4?

Hi all,

are there any plans that future versions of mkfs.btrfs will do an
initial pre-discard for SSDs? (AFAIK mkfs.btrfs does not do this
currently)

For Ext4, mke2fs does this with the -E discard option.
From the mke2fs manpage:
  -E discard
    Attempt to discard blocks at mkfs time (discarding blocks initially is
useful
    on solid state devices and sparse / thin-provisioned storage). When the
device
    advertises that discard also zeroes data (any subsequent read after the
discard
    and before write returns zero), then mark all not-yet-zeroed inode tables as
    zeroed. This significantly speeds up filesystem initialization. This is set
    as default.

Best regards,
Werner


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On Sun, Jul 3, 2011 at 6:00 PM, Werner Fischer <devlists@wefi.net>
wrote:
> Hi all,
>
> are there any plans that future versions of mkfs.btrfs will do an
> initial pre-discard for SSDs? (AFAIK mkfs.btrfs does not do this
> currently)
It should already have it. That is, if you look in the right place

commit e6bd18d8938986c997c45f0ea95b221d4edec095
Author: Christoph Hellwig <hch@lst.de>
Date:   Thu Apr 21 16:24:07 2011 -0400

    btrfs-progs: add discard support to mkfs

    Discard the whole device before starting to create the filesystem
structures.
    Modelled after similar support in mkfs.xfs.

    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Chris Mason <chris.mason@oracle.com>

IIRC it''s already in tmp branch of Chris''
btrfs-progs-unstable, but
not in master (yet).

-- 
Fajar
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