linux-kernel - Re: [PATCH v5 02/14] ntfs: update in-memory, on-disk structures and headers

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Message-ID: <20260120064032.GA3350@lst.de>
Date: Tue, 20 Jan 2026 07:40:32 +0100
From: Christoph Hellwig <hch@....de>
To: Namjae Jeon <linkinjeon@...nel.org>
Cc: Christoph Hellwig <hch@....de>, viro@...iv.linux.org.uk,
	brauner@...nel.org, tytso@....edu, willy@...radead.org,
	jack@...e.cz, djwong@...nel.org, josef@...icpanda.com,
	sandeen@...deen.net, rgoldwyn@...e.com, xiang@...nel.org,
	dsterba@...e.com, pali@...nel.org, ebiggers@...nel.org,
	neil@...wn.name, amir73il@...il.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, iamjoonsoo.kim@....com,
	cheol.lee@....com, jay.sim@....com, gunho.lee@....com
Subject: Re: [PATCH v5 02/14] ntfs: update in-memory, on-disk structures
 and headers

On Tue, Jan 20, 2026 at 01:27:55PM +0900, Namjae Jeon wrote:
> On Mon, Jan 19, 2026 at 4:05 PM Christoph Hellwig <hch@....de> wrote:
> >
> > On Sun, Jan 18, 2026 at 01:54:06PM +0900, Namjae Jeon wrote:
> > > > It seem like big_ntfs_inode is literally only used in the conversion
> > > > helpers below.  Are there are a lot of these "extent inode" so that
> > > > not having the vfs inode for them is an actual saving?
> > > Right, In NTFS, a base MFT record (represented by the base ntfs_inode)
> > > requires a struct inode to interact with the VFS. However, a single
> > > file can have multiple extent MFT records to store additional
> > > attributes. These extent inodes are managed internally by the base
> > > inode and do not need to be visible to the VFS.
> >
> > What are typical numbers of the extra extent inodes?  If they are rare,
> > you might be able to simplify the code a bit by just always allocating
> > the vfs_inode even if it's not really used.
> Regarding the typical numbers, in most cases, It will require zero or
> only a few extra extent inodes. Okay, I will move vfs_inode to
> ntfs_inode.

This was just thinking out loud.  If it doesn't help to significantly
simplify things, don't bother.