linux-kernel - Re: [RFC PATCH v2 0/8] fallocate: introduce FALLOC_FL_WRITE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <a8ea2143-0b10-43ba-a464-7ce3348bb5af@huaweicloud.com>
Date: Thu, 16 Jan 2025 11:04:36 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: Chaitanya Kulkarni <chaitanyak@...dia.com>
Cc: "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
 "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
 "dm-devel@...ts.linux.dev" <dm-devel@...ts.linux.dev>,
 "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
 "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
 "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "hch@....de" <hch@....de>, "tytso@....edu" <tytso@....edu>,
 "djwong@...nel.org" <djwong@...nel.org>,
 "yi.zhang@...wei.com" <yi.zhang@...wei.com>,
 "chengzhihao1@...wei.com" <chengzhihao1@...wei.com>,
 "yukuai3@...wei.com" <yukuai3@...wei.com>,
 "yangerkun@...wei.com" <yangerkun@...wei.com>,
 Shinichiro Kawasaki <shinichiro.kawasaki@....com>
Subject: Re: [RFC PATCH v2 0/8] fallocate: introduce FALLOC_FL_WRITE_ZEROES
 flag

On 2025/1/16 5:07, Chaitanya Kulkarni wrote:
> On 1/15/25 03:46, Zhang Yi wrote:
>> Currently, we can use the fallocate command to quickly create a
>> pre-allocated file. However, on most filesystems, such as ext4 and XFS,
>> fallocate create pre-allocation blocks in an unwritten state, and the
>> FALLOC_FL_ZERO_RANGE flag also behaves similarly. The extent state must
>> be converted to a written state when the user writes data into this
>> range later, which can trigger numerous metadata changes and consequent
>> journal I/O. This may leads to significant write amplification and
>> performance degradation in synchronous write mode. Therefore, we need a
>> method to create a pre-allocated file with written extents that can be
>> used for pure overwriting. At the monent, the only method available is
>> to create an empty file and write zero data into it (for example, using
>> 'dd' with a large block size). However, this method is slow and consumes
>> a considerable amount of disk bandwidth, we must pre-allocate files in
>> advance but cannot add pre-allocated files while user business services
>> are running.
> 
> it will be very useful if we can get some blktests for scsi/nvme/dm.
> Please note that this not a blocker to get this path series to be merged,
> but this will help everyone including regular tests runs we do to ensure
> the stability of new interface.

Hello, Chaitanya,

Thanks for your feedback! Yeah, the proposal for this series is still under
discussion, I will add counterpart tests to both blktests and fstests once
the solution is determined.

> 
> if you do please CC and Shinichiro (added to CC list) to we can help those
> tests review and potentially also can provide tested by tag tht can help
> this work to move forward.
> 
Sure, this will be very helpful.

Thanks,
Yi.