linux-ext4 - Re: [PATCH 2/2] Add batched discard support for ext4

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Message-ID: <87tyo2a2f7.fsf@dmon-lap.sw.ru>
Date:	Wed, 14 Jul 2010 12:33:00 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	eshishki@...hat.com, jmoyer@...hat.com, rwheeler@...hat.com,
	linux-ext4@...r.kernel.org, sandeen@...hat.com
Subject: Re: [PATCH 2/2] Add batched discard support for ext4

Lukas Czerner <lczerner@...hat.com> writes:

> Walk through each allocation group and trim all free extents. It can be
> invoked through TRIM ioctl on the file system. The main idea is to
> provide a way to trim the whole file system if needed, since some SSD's
> may suffer from performance loss after the whole device was filled (it
> does not mean that fs is full!).
>
> It search fro free extents in each allocation group. When the free
> extent is found, blocks are marked as used and then trimmed. Afterwards
> these blocks are marked as free in per-group bitmap.
Looks ok, except two small notes:
1) trim_fs is a time consuming operation and we have to add
   condresced, and signal_pending checks to allow user to interrupt
   cmd if necessery. See patch attached.
2) IMHO runtime trim support is useful sometimes, for example when
   user really care about data security i.e. unlinked file should be
   trimmed ASAP. I think we have to provide 'secdel' mount option
   similar to secdeletion flag for inode, but this is another story
   not directly connected with the patch.


View attachment "0001-ext4-Add-interrupt-points-to-batched-discard.patch" of type "text/x-diff" (2231 bytes)