Flash filesystem questions

[Erik Ekman]

Hi all,

I am working on a Linux driver for the Intel Turbo Memory Controller (8086:444e)
PCIe device. It was sold as a card to speed up the boot and operation of Vista
computers a few years ago.
More info at http://en.wikipedia.org/wiki/Intel_Turbo_Memory

I expected it to have a flash translation layer and expose a block device, but
instead I found access to raw flash operations (read, write & erase). I have
not found any way to access the OOB data, that is probably handled inside the
controller chip.  I have it basically working now, with 4kB pages and 128kB
erase blocks, and nandtest runs without errors.

The code is here: https://github.com/yarrick/turbomem

I am now trying to run a filesystem on top. JFFS2 was not happy with no OOB.
I found that the flash in the device only allows one write cycle per erase
(which seems normal according to YAFFS2 docs). ubiformat succeeded but then
ubiattach fails for me with an assert:

UBI: attaching mtd0 to ubi0
UBI: scanning is finished
UBI assert failed in ubi_io_read at 206 (pid 2743)
CPU: 1 PID: 2743 Comm: ubiattach Tainted: G       OE  3.17.7-300.fc21.x
Hardware name: LENOVO 7454GKU/7454GKU, BIOS 6DET64WW (3.14 ) 06/23/2010
 0000000000000000 000000003491b1e7 ffff880062b43ca0 ffffffff817401ea
 ffff880087c78000 ffff880062b43d10 ffffffffa08117fe 8000000000000163
 ffff880098163c00 ffffc90004806000 0000000000002000 0000000000006000
Call Trace:
 [<ffffffff817401ea>] dump_stack+0x45/0x56
 [<ffffffffa08117fe>] ubi_io_read+0x35e/0x3f0 [ubi]
 [<ffffffffa08069ff>] ubi_read_volume_table+0x11f/0xb90 [ubi]
 [<ffffffff8173ea9d>] ? printk+0x72/0x8e
 [<ffffffffa08181db>] ubi_attach+0xa4b/0x1470 [ubi]
 [<ffffffff811d28cf>] ? __vmalloc_node_range+0x1bf/0x290
 [<ffffffffa080aca0>] ubi_attach_mtd_dev+0x890/0x1010 [ubi]
 [<ffffffffa07f6c6d>] ? __get_mtd_device+0x1d/0x80 [mtd]
 [<ffffffff81745062>] ? mutex_lock+0x12/0x30
 [<ffffffffa080bd03>] ctrl_cdev_ioctl+0xc3/0x1f0 [ubi]
 [<ffffffff81220ff0>] do_vfs_ioctl+0x2d0/0x4b0
 [<ffffffff81221251>] SyS_ioctl+0x81/0xa0
 [<ffffffff81135d96>] ? __audit_syscall_exit+0x1f6/0x2a0
 [<ffffffff817473a9>] system_call_fastpath+0x16/0x1b

Could this problem be because of my driver? Is there some way to configure UBI
for to only write once per flash block or is that the default?
Will UBI or any other flash filesystem work properly without access to OOB data?
Is it worth to try YAFFS2?

I am using Fedora 21 and kernel 3.17.7-300.fc21.x86_64 now.

Thanks,

Erik