Mounting bfs via fuse not working

[Alexco]

On my FreeBSD12.1 setup I downloaded the latest haiku sources and build the bfs_fuse module. When I try to mount my bfs partition (only bfs partition on this machine, and haiku beta2 boots up from there without issues), I get the following error:

bfs_fuse /dev/ada0p8 ~/haiku
bfs: Disk size (138976911360 bytes) < file system size (138977214464 bytes)!
bfs: Mount:207: Invalid argument
bfs: bfs_mount:184: Invalid argument
Error: Mounting FS failed: Invalid argument

But my partition is fine (output of gpart list):

Name: ada0p8
Mediasize: 138977214464 (129G)
Sectorsize: 512
Stripesize: 4096
Stripeoffset: 0
Mode: r0w0e0
efimedia: HD(8,GPT,345c2ac9-ac6e-a24d-ae52-7f53eb4aab7b,0x27b65800,0x102dd800)
rawuuid: 345c2ac9-ac6e-a24d-ae52-7f53eb4aab7b
rawtype: 42465331-3ba3-10f1-802a-4861696b7521
label: Haiku
length: 138977214464
offset: 341125890048
type: !42465331-3ba3-10f1-802a-4861696b7521
index: 8
end: 937701375
start: 666261504

So where is the difference of 592 blocks/303104 bytes coming from? I must admit that I didn't understand the code at all...

[madmax]

From what I see, file system size comes from the fs superblock, and given gpart output it seems correct. Disk size would come from the GET_GEOMETRY ioctl which, if I'm right, would be managed in ​unistd.cpp, and that hasn't changed recently for FreeBSD. It uses some ioctls to get cylinders, sectors per track, etc. And indeed the value fits nicely in a CHS scheme: 138976911360 = 512 * 63 * 16 * 269285, but it's not the real value. As found in FreeBSD's disk.h for two of those ioctl:

This value is mostly used for compatibility with various ill designed disk label formats. Don't use it unless you have to.

It seems for Linux a fake geometry is first tried from just the total size if available. Can't a similar thing be done for FreeBSD from DIOCGMEDIASIZE?

Given diver's comment in #16171 and the code, darwin is also affected. It uses size, but tries a more typical CHS configuration than in Linux when BLKGETSIZE64 works.

[Alexco]

Sorry, I already wrote that here ​https://discuss.haiku-os.org/t/compiling-bfs-for-fuse/9566. The C/H/S conversion does not work correctly, since a sector number of 63 is returned, which results in rounding errors. I still wonder why we need to do stupid CHS conversions and just can't forward the media size. Is Haiku internally still using CHS? By the way, I used a similar fake geometry for FreeBSD as used for Linux and this works, but I was too lazy to prepare a patch so far...