From: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To: John Garry <john.g.garry@oracle.com>,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
Dave Chinner <david@fromorbit.com>
Cc: Ojaswin Mujoo <ojaswin@linux.ibm.com>, Jan Kara <jack@suse.cz>,
Theodore Ts'o <tytso@mit.edu>,
Matthew Wilcox <willy@infradead.org>,
"Darrick J . Wong" <djwong@kernel.org>,
Luis Chamberlain <mcgrof@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC 0/9] ext4: Add direct-io atomic write support using fsawu
Date: Wed, 06 Mar 2024 18:43:40 +0530 [thread overview]
Message-ID: <87il1zpkor.fsf@doe.com> (raw)
In-Reply-To: <e4bd58d4-723f-4c94-bf46-826bceeb6a8d@oracle.com>
John Garry <john.g.garry@oracle.com> writes:
> On 02/03/2024 07:41, Ritesh Harjani (IBM) wrote:
>> Hello all,
>>
>> This RFC series adds support for atomic writes to ext4 direct-io using
>> filesystem atomic write unit. It's built on top of John's "block atomic
>> write v5" series which adds RWF_ATOMIC flag interface to pwritev2() and enables
>> atomic write support in underlying device driver and block layer.
>>
>> This series uses the same RWF_ATOMIC interface for adding atomic write support
>> to ext4's direct-io path. One can utilize it by 2 of the methods explained below.
>> ((1)mkfs.ext4 -b <BS>, (2) with bigalloc).
>>
>> Filesystem atomic write unit (fsawu):
>> ============================================
>> Atomic writes within ext4 can be supported using below 3 methods -
>> 1. On a large pagesize system (e.g. Power with 64k pagesize or aarch64 with 64k pagesize),
>> we can mkfs using different blocksizes. e.g. mkfs.ext4 -b <4k/8k/16k/32k/64k).
>> Now if the underlying HW device supports atomic writes, than a corresponding
>> blocksize can be chosen as a filesystem atomic write unit (fsawu) which
>> should be within the underlying hw defined [awu_min, awu_max] range.
>> For such filesystem, fsawu_[min|max] both are equal to blocksize (e.g. 16k)
>>
>> On a smaller pagesize system this can be utilized when support for LBS is
>> complete (on ext4).
>>
>> 2. EXT4 already supports a feature called bigalloc. In that ext4 can handle
>> allocation in cluster size units. So for e.g. we can create a filesystem with
>> 4k blocksize but with 64k clustersize. Such a configuration can also be used
>> to support atomic writes if the underlying hw device supports it.
>> In such case the fsawu_min will most likely be the filesystem blocksize and
>> fsawu_max will mostly likely be the cluster size.
>>
>> So a user can do an atomic write of any size between [fsawu_min, fsawu_max]
>> range as long as it satisfies other constraints being laid out by HW device
>> (or by software stack) to support atomic writes.
>> e.g. len should be a power of 2, pos % len should be naturally
>> aligned and [start | end] (phys offsets) should not straddle over
>> an atomic write boundary.
>
> JFYI, I gave this a quick try, and it seems to work ok. Naturally it
Thanks John for giving this a try!
> suffers from the same issue discussed at
> https://lore.kernel.org/linux-fsdevel/434c570e-39b2-4f1c-9b49-ac5241d310ca@oracle.com/
> with regards to writing to partially written extents, which I have tried
> to address properly in my v2 for that same series.
I did go through other revisions, but I guess I missed going through this series.
Thanks Dave & John for your comments over the series.
Let me go through the revisions I have missed and John's latest revision.
I will update this series accordingly.
Appreciate your help!
-ritesh
next prev parent reply other threads:[~2024-03-06 13:13 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-02 7:41 [RFC 0/9] ext4: Add direct-io atomic write support using fsawu Ritesh Harjani (IBM)
2024-03-02 7:41 ` [RFC 1/8] fs: Add FS_XFLAG_ATOMICWRITES flag Ritesh Harjani (IBM)
2024-03-02 7:41 ` [RFC 2/8] fs: Reserve inode flag FS_ATOMICWRITES_FL for atomic writes Ritesh Harjani (IBM)
2024-03-04 0:59 ` Dave Chinner
2024-03-08 7:19 ` Ojaswin Mujoo
2024-03-02 7:42 ` [RFC 3/8] iomap: Add atomic write support for direct-io Ritesh Harjani (IBM)
2024-03-04 1:16 ` Dave Chinner
2024-03-04 5:33 ` Ritesh Harjani
2024-03-04 8:49 ` John Garry
2024-03-04 10:31 ` Ritesh Harjani
2024-03-04 20:56 ` Dave Chinner
2024-03-02 7:42 ` [RFC 4/8] ext4: Add statx and other atomic write helper routines Ritesh Harjani (IBM)
2024-03-06 11:14 ` John Garry
2024-03-08 8:10 ` Ritesh Harjani
2024-03-02 7:42 ` [RFC 5/8] ext4: Adds direct-io atomic writes checks Ritesh Harjani (IBM)
2024-03-02 7:42 ` [RFC 6/8] ext4: Add an inode flag for atomic writes Ritesh Harjani (IBM)
2024-03-04 20:34 ` Dave Chinner
2024-03-08 8:02 ` Ritesh Harjani
2024-03-02 7:42 ` [RFC 7/8] ext4: Enable FMODE_CAN_ATOMIC_WRITE in open for direct-io Ritesh Harjani (IBM)
2024-03-02 7:42 ` [RFC 8/8] ext4: Adds atomic writes using fsawu Ritesh Harjani (IBM)
2024-03-02 7:42 ` [RFC 9/9] e2fsprogs/chattr: Supports atomic writes attribute Ritesh Harjani (IBM)
2024-03-06 11:22 ` [RFC 0/9] ext4: Add direct-io atomic write support using fsawu John Garry
2024-03-06 13:13 ` Ritesh Harjani [this message]
2024-03-08 20:25 ` [RFC] ext4: Add support for ext4_map_blocks_atomic() Ritesh Harjani (IBM)
2024-03-09 2:37 ` Ritesh Harjani
2024-03-13 18:40 ` John Garry
2024-03-14 15:52 ` Ritesh Harjani
2024-03-18 8:22 ` John Garry
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