linux-kernel - Re: [RFC PATCH 03/24] erofs: add Errno in Rust

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Message-ID: <b89eec22-e79e-41a1-af0c-7d1251a5f0c3@linux.alibaba.com>
Date: Thu, 26 Sep 2024 19:05:02 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Ariel Miculas <amiculas@...co.com>
Cc: Gary Guo <gary@...yguo.net>, rust-for-linux@...r.kernel.org,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 linux-erofs@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>,
 Al Viro <viro@...iv.linux.org.uk>, Benno Lossin <benno.lossin@...ton.me>,
 linux-fsdevel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC PATCH 03/24] erofs: add Errno in Rust



On 2024/9/26 19:01, Ariel Miculas wrote:

..

> 
>> I believe they basically equal to your `Unified size`s, so
>> the result is
>>
>> 			Your unified size
>> 	EROFS (LZ4HC,12,64k)  54.2
>> 	PuzzleFS compressed   53?
>> 	EROFS (DEFLATE,9,32k) 46.4
>>
>> That is why I used your 53 unified size to show EROFS is much
>> smaller than PuzzleFS.
>>
>> The reason why EROFS and SquashFS doesn't have the `Total Size`s
>> is just because we cannot store every individual chunk into some
>> seperate file.
> 
> Well storing individual chunks into separate files is the entire point
> of PuzzleFS.
> 
>>
>> Currently, I have seen no reason to open arbitary kernel files
>> (maybe hundreds due to large folio feature at once) in the page
>> fault context.  If I modified `mkfs.erofs` tool, I could give
>> some similar numbers, but I don't want to waste time now due
>> to `open arbitary kernel files in the page fault context`.
>>
>> As I said, if PuzzleFS finally upstream some work to open kernel
>> files in page fault context, I will definitely work out the same
>> feature for EROFS soon, but currently I don't do that just
>> because it's very controversal and no in-tree kernel filesystem
>> does that.
> 
> The PuzzleFS kernel filesystem driver is still in an early POC stage, so
> there's still a lot more work to be done.

I suggest that you could just ask FS/MM folks about this ("open
kernel files when reading in the page fault")  first.

If they say "no", I suggest please don't waste on this anymore.

Thanks,
Gao Xiang

> 
> Regards,
> Ariel
> 
>>
>> Thanks,
>> Gao Xiang