Message-ID: <CAKYAXd-HPvJonfjsvmaHJ08TKh1QywqLO5fAQM8q7HHihK93PA@mail.gmail.com>
Date: Tue, 30 Dec 2025 00:14:39 +0900
From: Namjae Jeon <linkinjeon@...nel.org>
To: Amir Goldstein <amir73il@...il.com>
Cc: viro@...iv.linux.org.uk, brauner@...nel.org, hch@...radead.org, hch@....de, 
	tytso@....edu, willy@...radead.org, jack@...e.cz, djwong@...nel.org, 
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	xiang@...nel.org, dsterba@...e.com, pali@...nel.org, ebiggers@...nel.org, 
	neil@...wn.name, 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 v3 00/12] ntfs filesystem remake

On Mon, Dec 29, 2025 at 11:34 PM Amir Goldstein <amir73il@...il.com> wrote:
>
> On Mon, Dec 29, 2025 at 2:45 PM Namjae Jeon <linkinjeon@...nel.org> wrote:
> >
> > Introduction
> > ============
> >
> > The NTFS filesystem[1] still remains the default filesystem for Windows
> > and The well-maintained NTFS driver in the Linux kernel enhances
> > interoperability with Windows devices, making it easier for Linux users
> > to work with NTFS-formatted drives. Currently, ntfs support in Linux was
> > the long-neglected NTFS Classic (read-only), which has been removed from
> > the Linux kernel, leaving the poorly maintained ntfs3. ntfs3 still has
> > many problems and is poorly maintained, so users and distributions are
> > still using the old legacy ntfs-3g.
> >
> > The remade ntfs is an implementation that supports write and the essential
> > requirements(iomap, no buffer-head, utilities, xfstests test result) based
> > on read-only classic NTFS.
> > The old read-only ntfs code is much cleaner, with extensive comments,
> > offers readability that makes understanding NTFS easier. This is why
> > new ntfs was developed on old read-only NTFS base.
> > The target is to provide current trends(iomap, no buffer head, folio),
> > enhanced performance, stable maintenance, utility support including fsck.
> >
> >
> > Key Features
> > ============
> >
> > - Write support:
> >    Implement write support on classic read-only NTFS. Additionally,
> >    integrate delayed allocation to enhance write performance through
> >    multi-cluster allocation and minimized fragmentation of cluster bitmap.
> >
> > - Switch to using iomap:
> >    Use iomap for buffered IO writes, reads, direct IO, file extent mapping,
> >    readpages, writepages operations.
> >
> > - Stop using the buffer head:
> >    The use of buffer head in old ntfs and switched to use folio instead.
> >    As a result, CONFIG_BUFFER_HEAD option enable is removed in Kconfig also.
> >
> > - Public utilities include fsck[2]:
> >    While ntfs-3g includes ntfsprogs as a component, it notably lacks
> >    the fsck implementation. So we have launched a new ntfs utilitiies
> >    project called ntfsprogs-plus by forking from ntfs-3g after removing
> >    unnecessary ntfs fuse implementation. fsck.ntfs can be used for ntfs
> >    testing with xfstests as well as for recovering corrupted NTFS device.
> >
> > - Performance Enhancements:
> >
> >    - ntfs vs. ntfs3:
> >
> >      * Performance was benchmarked using iozone with various chunk size.
> >         - In single-thread(1T) write tests, ntfs show approximately
> >           3~5% better performance.
> >         - In multi-thread(4T) write tests, ntfs show approximately
> >           35~110% better performance.
> >         - Read throughput is identical for both ntfs implementations.
> >
> >      1GB file      size:4096           size:16384           size:65536
> >      MB/sec       ntfs | ntfs3        ntfs | ntfs3        ntfs | ntfs3
> >      ─────────────────────────────────────────────────────────────────
> >      read          399 | 399           426 | 424           429 | 430
> >      ─────────────────────────────────────────────────────────────────
> >      write(1T)     291 | 276           325 | 305           333 | 317
> >      write(4T)     105 | 50            113 | 78            114 | 99.6
> >
> >
> >      * File list browsing performance. (about 12~14% faster)
> >
> >                   files:100000        files:200000        files:400000
> >      Sec          ntfs | ntfs3        ntfs | ntfs3        ntfs | ntfs3
> >      ─────────────────────────────────────────────────────────────────
> >      ls -lR       7.07 | 8.10        14.03 | 16.35       28.27 | 32.86
> >
> >
> >      * mount time.
> >
> >              parti_size:1TB      parti_size:2TB      parti_size:4TB
> >      Sec          ntfs | ntfs3        ntfs | ntfs3        ntfs | ntfs3
> >      ─────────────────────────────────────────────────────────────────
> >      mount        0.38 | 2.03         0.39 | 2.25         0.70 | 4.51
> >
> >    The following are the reasons why ntfs performance is higher
> >     compared to ntfs3:
> >      - Use iomap aops.
> >      - Delayed allocation support.
> >      - Optimize zero out for newly allocated clusters.
> >      - Optimize runlist merge overhead with small chunck size.
> >      - pre-load mft(inode) blocks and index(dentry) blocks to improve
> >        readdir + stat performance.
> >      - Load lcn bitmap on background.
> >
> > - Stability improvement:
> >    a. Pass more xfstests tests:
> >       ntfs passed 287 tests, significantly higher than ntfs3's 218.
> >       ntfs implement fallocate, idmapped mount and permission, etc,
> >       resulting in a significantly high number of xfstests passing compared
> >       to ntfs3.
> >    b. Bonnie++ issue[3]:
> >       The Bonnie++ benchmark fails on ntfs3 with a "Directory not empty"
> >       error during file deletion. ntfs3 currently iterates directory
> >       entries by reading index blocks one by one. When entries are deleted
> >       concurrently, index block merging or entry relocation can cause
> >       readdir() to skip some entries, leaving files undeleted in
> >       workloads(bonnie++) that mix unlink and directory scans.
> >       ntfs implement leaf chain traversal in readdir to avoid entry skip
> >       on deletion.
> >
> > - Journaling support:
> >    ntfs3 does not provide full journaling support. It only implement journal
> >    replay[4], which in our testing did not function correctly. My next task
> >    after upstreaming will be to add full journal support to ntfs.
> >
> >
> > The feature comparison summary
> > ==============================
> >
> > Feature                               ntfs       ntfs3
> > ===================================   ========   ===========
> > Write support                         Yes        Yes
> > iomap support                         Yes        No
> > No buffer head                        Yes        No
> > Public utilities(mkfs, fsck, etc.)    Yes        No
> > xfstests passed                       287        218
> > Idmapped mount                        Yes        No
> > Delayed allocation                    Yes        No
> > Bonnie++                              Pass       Fail
> > Journaling                            Planned    Inoperative
> > ===================================   ========   ===========
>
> For completion of this report, are the 287 passed xfstests a super set
> of the 218
> passed xfstest for ntfs3?
> IOW, are there any known functional regressions from ntfs3 to ntfs?
There are 9 testcases that passed in ntfs3 but fail in ntfs.
I will fix them on v4.
Thanks!
>
> Thanks,
> Amir.

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