Re: f2fs bug: Unable to mount big volumes in kernel 4.5

[David Gnedt <david.gnedt@davizone.at>]

Hello,

> Following commit in dev branch of f2fs-tools has fixed this issue, could you
test this
> patch firstly?
> ("mkfs.f2fs: set segment_count in super block correctly")

Sorry, I cannot recreate the volume on the 8TB Seagate drive right now, but I
did a test with a loopback device of equal size.

Should I be worried about the changes in mkfs.f2fs since 1.6.0? Would it be
suggested to recreate the filesystem? Or is it maybe possible to manually fix it?
If it is really only the alignment, I think it shouldn't matter for SMR drives,
as they are not using constant size zones anyway, so misalignment cannot be
avoided with f2fs.

>> Could you test the attached patch?

I did a roundup test of all kernel/f2fs-tools version I thought that make sense.
I hope the patch will be included in upcoming mainline kernels.

Short summary:
--------------
Filesystems created with a recent dev version of f2fs-tools work without any
problems and don't need the f2fs kernel patch.
Filesystems created with older f2fs-tools need the f2fs kernel patch to mount
correctly.
I guess that is exactly what everyone expected to be the outcome.

Full details:
-------------
f2fs-tools D:  release 1.6.0 (Seagate SMR drive)
f2fs-tools L1: release 1.6.0 (Loopback)
f2fs-tools L2: 2016-01-08 mkfs.f2fs: introduce zone align for main area (Loopback)
f2fs-tools L3: 2016-03-16 mkfs.f2fs: set segment_count in super block correctly
(Loopback)

Test procedure:
$ truncate -s 8001559724032 f2fs-tools-1.6.0.img
$ losetup -f f2fs-tools-1.6.0.img
$ mkfs.f2fs -s64 -t0 -a0 /dev/loop0
$ mount -t f2fs -onoinline_data,noatime,flush_merge,no_heap,ro /dev/loop0 /mnt
$ umount /mnt

Kernel: Linux 4.4.6 x86_64
f2fs-tools D:  Works
f2fs-tools L1: Works
f2fs-tools L2: Works
f2fs-tools L3: Works

Kernel: Linux 4.5.0 x86_64
f2fs-tools D:  Failed -> Same errors as before
f2fs-tools L1: Failed -> Same errors as before
f2fs-tools L2: Failed -> Same errors as before
f2fs-tools L3: Works

Kernel: Linux 4.5.0+patch x86_64
f2fs-tools D:  Works
f2fs-tools L1: Works
f2fs-tools L2: Works
f2fs-tools L3: Works

Best regards,
David Gnedt

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