linux-ext4 - [BISECTED] unable to mount devices larger than 16 TB (was: [Bug 207367] Accraid / aptec / Microsemi / ext4 / larger then 16TB)

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Date:   Mon, 20 Apr 2020 20:55:15 -0700 (PDT)
From:   Christian Kujau <lists@...dbynature.de>
To:     linux-ext4@...r.kernel.org
cc:     Ritesh Harjani <riteshh@...ux.ibm.com>, Jan Kara <jack@...e.cz>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Theodore Ts'o <tytso@....edu>, walter.moeller@...ller-it.net
Subject: [BISECTED] unable to mount devices larger than 16 TB (was: [Bug
 207367] Accraid / aptec / Microsemi / ext4 / larger then 16TB)

On Mon, 20 Apr 2020, Christian Kujau wrote:
> On Mon, 20 Apr 2020, bugzilla-daemon@...zilla.kernel.org wrote:
> > with kernel 5.7 only volumes under 16TB can be mount.
> 
> While this bug report is still missing details, I was able to reproduce 
> this issue. Contrary to the subject line, it is not hardware related at 
> all.

A git bisect run pointed to:

-------------------------------------------------------------------------  
  commit ac58e4fb03f9d111d733a4ad379d06eef3a24705
  Author: Ritesh Harjani <riteshh@...ux.ibm.com>
  Date:   Fri Feb 28 14:56:56 2020 +0530

    ext4: move ext4 bmap to use iomap infrastructure
    
    ext4_iomap_begin is already implemented which provides ext4_map_blocks,
    so just move the API from generic_block_bmap to iomap_bmap for iomap
    conversion.
--------------------------------------------------------------------------  

With only this commit reverted, v5.7-rc2 is able mount (and access) large 
ext4 filesystems again.

Thanks to Walter Moeller for reporting this in the first place.

HTH,
Christian.

> Linux 5.5 (Debian), creating a 17 TB sparse device (4 GB backing device):
> 
>  $ echo "0 36507222016 zero" | dmsetup create zero0
>  $ echo "0 36507222016 snapshot /dev/mapper/zero0 /dev/vdb p 128" | \
>    dmsetup create sparse0
>  
>  $ mkfs.ext4 -F /dev/mapper/sparse0
>  Creating filesystem with 4563402752 4k blocks and 285212672 inodes
>  Creating journal (262144 blocks): done
>  
>  $ mount -t ext4 /dev/mapper/sparse0 /mnt/disk/
>  $ df -h /mnt/disk/
>  Filesystem      Size  Used Avail Use% Mounted on
>  /dev/mapper/sparse0   17T   24K   17T   1% /mnt/disk
> 
> 
> The same fails on 5.7-rc2 (vanilla) with:
> 
> 
> ------------[ cut here ]------------
> would truncate bmap result
> WARNING: CPU: 0 PID: 640 at fs/iomap/fiemap.c:121 
> iomap_bmap_actor+0x3a/0x40
> Modules linked in: dm_zero 9p xhci_pci xhci_hcd virtio_balloon 
> 9pnet_virtio loop fuse sunrpc
> CPU: 0 PID: 640 Comm: mount Not tainted 5.7.0-rc2 #3
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
> ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 
> 04/01/2014
> RIP: 0010:iomap_bmap_actor+0x3a/0x40
> Code: 70 08 0f b6 8f 86 00 00 00 49 03 30 48 d3 ee 48 81 fe ff ff ff 7f 77 
> 06 48 89 30 31 c0 c3 48 c7 c7 fa 71 56 a9 e8 04 f7 ea ff <0f> 0b 31 c0 c3 
> cc 41 54 55 53 48 83 ec 08 48 8b 47 48 48 89 34 24
> RSP: 0018:ffffb8fd8090bb80 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: ffffffffa9424bb0 RCX: 0000000000000000
> RDX: ffff996abbc1ed40 RSI: ffff996abbc180c8 RDI: ffff996abbc180c8
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000277
> R10: 0000000000000774 R11: ffffb8fd8090ba35 R12: 0000000000000000
> R13: ffff996aafc6e9b8 R14: ffffb8fd8090bc70 R15: 0000000000001000
> FS:  00007efc34fafc80(0000) GS:ffff996abbc00000(0000) 
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007efc352f29a0 CR3: 000000016e074003 CR4: 0000000000360eb0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  iomap_apply+0xf4/0x1a0
>  ? iomap_fiemap_actor+0x90/0x90
>  iomap_bmap+0x70/0x90
>  ? iomap_fiemap_actor+0x90/0x90
>  bmap+0x1d/0x30
>  jbd2_journal_init_inode+0x2b/0xe0
>  ext4_fill_super+0x29c4/0x3300
>  ? mount_bdev+0x171/0x1a0
>  ? ext4_calculate_overhead+0x480/0x480
>  mount_bdev+0x171/0x1a0
>  ? ext4_calculate_overhead+0x480/0x480
>  legacy_get_tree+0x22/0x40
>  vfs_get_tree+0x1b/0x80
>  ? ns_capable_common+0x29/0x50
>  do_mount+0x713/0x9f0
>  ? memdup_user+0x49/0x90
>  __x64_sys_mount+0x89/0xc0
>  do_syscall_64+0x60/0x3b0
>  ? do_page_fault+0x243/0x4bb
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x7efc351c7e1a
> Code: 48 8b 0d 79 e0 0b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 
> 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff 
> ff 73 01 c3 48 8b 0d 46 e0 0b 00 f7 d8 64 89 01 48
> RSP: 002b:00007ffe6e5bce18 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 000055d888f5cb00 RCX: 00007efc351c7e1a
> RDX: 000055d888f5cd10 RSI: 000055d888f5ea30 RDI: 000055d888f5cd30
> RBP: 00007efc35318204 R08: 0000000000000000 R09: 000055d888f5ee00
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000000000 R14: 000055d888f5cd30 R15: 000055d888f5cd10
> ---[ end trace 513dea1cc94aa289 ]---
> jbd2_journal_init_inode: Cannot locate journal superblock
> EXT4-fs (dm-1): Could not load journal inode
> 
> 
> HTH,
> Christian.
> -- 
> BOFH excuse #306:
> 
> CPU-angle has to be adjusted because of vibrations coming from the nearby road
> 

-- 
BOFH excuse #29:

It works the way the Wang did, what's the problem