Date:	Mon, 6 Jun 2011 15:08:26 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	amir73il@...rs.sourceforge.net
cc:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH RFC 00/30] Ext4 snapshots - core patches

On Mon, 9 May 2011, amir73il@...rs.sourceforge.net wrote:
> 
> MERGING
> -------
> These patches are based on Ted's current master branch + alloc_semp removal
> patches. Although the alloc_semp removal is an independent (and in my eyes
> a good) change, it is also required by snapshot patches, to avoid circular
> locking dependency during COW allocations.
> 
> Merging with Allison's punch holes patches should be straight forward, since
> the hard part, namely Yongqiang's split extent refactoring patches, was
> already merged by Ted.
> 
> Merging with Ted's big alloc patches is going to be a bit more challenging,
> since big alloc patches make a lot of renaming and refactoring. However,
> since has_snapshots and big_alloc features will never work together,
> at least testing the code together is not a big concern.

Hi Amir,

what is the reason for the snapshots to never work with big_alloc ? Just
out of curiosity.

> 
> TESTING
> -------
> Apart from the extensive testing for the snapshots feature functionality, we
> also ran xfstests with snapshots and while taking a snapshot every 1 minute.

Since a lot of the tests are actually shorter than one minute, you miss a
lot of possible concurrent operations. Is there any reason why not to do
it more often ? Let's say every second ?

> More importantly, we ran xfstests with snapshots support disabled in compile
> time and with snapshot support enabled but without has_snapshot feature.
> These xfstests were run with blocksize 1K and 4K and on X86 and X86_64.
> The 1K blocksize tests are important for the alloc_semp removal patches.
> No problems were found apart from one (test 225 hung), which is already
> existing in master branch.
> 
> CREDITS
> -------
> The snapshots patches originate in my implementation of the Next3 filesystem
> for CTERA networks.
> The porting of the Next3 snapshot patches to ext4 patches is attributed to
> Aditya Dani, Shardul Mangade, Piyush Nimbalkar and Harshad Shirwadkar from
> the Pune Institute of Computer Technology (PICT).
> The implementation of extents move-on-write, delayed move-on-write and much
> of the cleanup work on these patches was carried out by Yongqiang Yang from
> the Institute of Computing Technology, Chinese Academy of Sciences.
> 
> 
> [PATCH RFC 01/30] ext4: EXT4 snapshots (Experimental)
> [PATCH RFC 02/30] ext4: snapshot debugging support
> [PATCH RFC 03/30] ext4: snapshot hooks - inside JBD hooks
> [PATCH RFC 04/30] ext4: snapshot hooks - block bitmap access
> [PATCH RFC 05/30] ext4: snapshot hooks - delete blocks
> [PATCH RFC 06/30] ext4: snapshot hooks - move data blocks
> [PATCH RFC 07/30] ext4: snapshot hooks - direct I/O
> [PATCH RFC 08/30] ext4: snapshot hooks - move extent file data blocks
> [PATCH RFC 09/30] ext4: snapshot file
> [PATCH RFC 10/30] ext4: snapshot file - read through to block device
> [PATCH RFC 11/30] ext4: snapshot file - permissions
> [PATCH RFC 12/30] ext4: snapshot file - store on disk
> [PATCH RFC 13/30] ext4: snapshot file - increase maximum file size limit to 16TB
> [PATCH RFC 14/30] ext4: snapshot block operations
> [PATCH RFC 15/30] ext4: snapshot block operation - copy blocks to snapshot
> [PATCH RFC 16/30] ext4: snapshot block operation - move blocks to snapshot
> [PATCH RFC 17/30] ext4: snapshot control
> [PATCH RFC 18/30] ext4: snapshot control - fix new snapshot
> [PATCH RFC 19/30] ext4: snapshot control - reserve disk space for snapshot
> [PATCH RFC 20/30] ext4: snapshot journaled - increase transaction credits
> [PATCH RFC 21/30] ext4: snapshot journaled - implement journal_release_buffer()
> [PATCH RFC 22/30] ext4: snapshot journaled - bypass to save credits
> [PATCH RFC 23/30] ext4: snapshot journaled - trace COW/buffer credits
> [PATCH RFC 24/30] ext4: snapshot list support
> [PATCH RFC 25/30] ext4: snapshot race conditions - concurrent COW operations
> [PATCH RFC 26/30] ext4: snapshot race conditions - tracked reads
> [PATCH RFC 27/30] ext4: snapshot exclude - the exclude bitmap
> [PATCH RFC 28/30] ext4: snapshot cleanup
> [PATCH RFC 29/30] ext4: snapshot cleanup - shrink deleted snapshots
> [PATCH RFC 30/30] ext4: snapshot rocompat - enable rw mount
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