Re: Fix SWSUSP & !SWAP

From: "H. Peter Anvin" <hpa@zytor.com>
To: Andreas Dilger <adilger@clusterfs.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Fix SWSUSP & !SWAP
Date: Thu, 24 Apr 2003 21:33:52 -0700	[thread overview]
Message-ID: <3EA8BAB0.4080003@zytor.com> (raw)
In-Reply-To: <20030424222737.X26054@schatzie.adilger.int>

Andreas Dilger wrote:
> 
> This "supersync" already exists, and it is supported by all of the
> journaling filesystems for LVM snapshots.  This is the VFS method
> write_super_lockfs in the ext3/reiserfs/XFS/JFS super_operations.
> Not only does it sync the dirty data to disk, but it also forces
> the journal to be empty and marks the filesystem clean, so that it
> can be snapshotted and read-only mounted (basically equivalent to
> unmounting the filesystem).
> 
> Unfortunately, even though the filesystems themselves have supported
> this VFS method for a long time, the actual code that calls these
> methods (sync_super_lockfs() and unlockfs()) are still only available
> as a patch from LVM.  The LVM/reiserfs folks have talked about submitting
> it to Marcelo for a long time now, but apparently still haven't done so.
> 

I really think this should be made available.  Perhaps we should have a 
sync1() system call which takes a flag set.  Then we could have 
sync1(SYNC_FLUSH_JOURNALS);

	-hpa