From: Theodore Tso <tytso@mit.edu>
To: Jan Kara <jack@suse.cz>
Cc: Ext4 Developers List <linux-ext4@vger.kernel.org>,
Linux Kernel Developers List <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@infradead.org>,
Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [PATCH 1/5] ext4: Avoid races caused by on-line resizing and SMP memory reordering
Date: Tue, 28 Apr 2009 13:14:45 -0400 [thread overview]
Message-ID: <20090428171445.GD24043@mit.edu> (raw)
In-Reply-To: <20090428162359.GK21950@atrey.karlin.mff.cuni.cz>
On Tue, Apr 28, 2009 at 06:23:59PM +0200, Jan Kara wrote:
> Ouch... Hmm, smp_rmb() isn't completely free and mainly it's a bit
> ugly and prone to errors (I'm afraid next time someone changes the
> allocation code, we miss some barriers again)... so.. Maybe a stupid
> idea but wouldn't it be easier to solve the online resize like: freeze
> the filesystem, do all the changes required for extend, unfreeze the
> filesystem?
Eric suggested a helper function when reading from s_groups_count.
That would take care of the code maintenance headache. One problem
with using freeze/thaw is it won't work without a journal, and we do
support filesystems without journals in ext4. (Probably the best
solution for netbooks with crapola SSD's.)
As far as smb_rmb() not being free, it's essentially free for
x86/x86_64 platforms. Is it really that costly on other
architectures?
- Ted
next prev parent reply other threads:[~2009-04-28 17:14 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-26 3:49 [PATCH RFC 0/5] Eliminate most lock_super() calls from ext4 Theodore Ts'o
2009-04-26 3:49 ` [PATCH 1/5] ext4: Avoid races caused by on-line resizing and SMP memory reordering Theodore Ts'o
2009-04-26 3:49 ` [PATCH 2/5] ext4: Remove outdated comment about lock_super() Theodore Ts'o
2009-04-26 3:49 ` [PATCH 3/5] ext4: ext4_mark_recovery_complete() doesn't need to use lock_super Theodore Ts'o
2009-04-26 3:49 ` [PATCH 4/5] ext4: Replace lock/unlock_super() with an explicit lock for the orphan list Theodore Ts'o
2009-04-26 3:49 ` [PATCH 5/5] ext4: Replace lock/unlock_super() with an explicit lock for resizing Theodore Ts'o
2009-04-28 16:02 ` Jan Kara
2009-04-28 15:52 ` [PATCH 4/5] ext4: Replace lock/unlock_super() with an explicit lock for the orphan list Jan Kara
2009-04-26 7:07 ` [PATCH 3/5] ext4: ext4_mark_recovery_complete() doesn't need to use lock_super Christoph Hellwig
2009-04-26 11:46 ` Theodore Tso
2009-04-26 11:49 ` Christoph Hellwig
2009-04-26 11:49 ` Christoph Hellwig
2009-04-28 16:13 ` [PATCH 2/5] ext4: Remove outdated comment about lock_super() Jan Kara
2009-04-28 16:23 ` [PATCH 1/5] ext4: Avoid races caused by on-line resizing and SMP memory reordering Jan Kara
2009-04-28 17:14 ` Theodore Tso [this message]
2009-04-29 9:28 ` Jan Kara
2009-04-29 9:28 ` Jan Kara
2009-05-01 13:55 ` [PATCH v2] " Theodore Ts'o
2009-05-03 17:08 ` Jan Kara
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