/dev/hd2 is 2 GiB in size (backed by LVM), unformatted.
# mkfs.ext2 -o hurd /dev/hd2 mke2fs 1.41.7 (29-June-2009) hd2 count 1 re-open, hd2 count 2 ext2fs_check_if_mount: Can't check if filesystem is mounted due to missing mtab file while determining whether /dev/hd2 is mounted. re-open, hd2 count 3 re-open, hd2 count 4 re-open, hd2 count 5 Filesystem label= OS type: Hurd Block size=4096 (log=2) Fragment size=4096 (log=2) 131072 inodes, 524288 blocks 26214 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=536870912 16 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912 Assertion `copy->size <= PAGE_SIZE' failed in file "../gnumach-1-branch-Xen-branch/xen/block.c", line 536 Kernel Breakpoint trap, eip 0x20020a77 Stopped at 0x20020a76: int $3 db> trace 0x20020a76(2006abc1,2006ba03,2006782c,218,2e2be8d4) 0x20020ace(2006ba03,2006782c,218,2e3629a0,32000) 0x2003e9d5(2de04764,2e2be0b8,12,0,3fff80) 0x200476e6(2de5ad54,2e2db010,2e30a9a0,2de3a854,2de5ad44) 0x20021ed4(2de5ad44,2e2bb2e0,2e2bb2a0,0,0) 0x2005309d(129b8f0,3,38,28,e) 0x20006838(129b8f0,3,38,28,e) >>>>> user space <<<<< $ addr2line -i -f -e /boot/gnumach-xen 0x20020a76 0x20020ace 0x2003e9d5 0x200476e6 0x20021ed4 0x2005309d 0x20006838 Debugger /home/tschwinge/tmp/gnumach/gnumach-1-branch-Xen-branch.build/../gnumach-1-branch-Xen-branch/kern/debug.c:105 Assert ??:0 device_write /home/tschwinge/tmp/gnumach/gnumach-1-branch-Xen-branch.build/../gnumach-1-branch-Xen-branch/xen/block.c:537 _Xdevice_write /home/tschwinge/tmp/gnumach/gnumach-1-branch-Xen-branch.build/device/device.server.c:253 ipc_kobject_server /home/tschwinge/tmp/gnumach/gnumach-1-branch-Xen-branch.build/../gnumach-1-branch-Xen-branch/kern/ipc_kobject.c:201 mach_msg_trap /home/tschwinge/tmp/gnumach/gnumach-1-branch-Xen-branch.build/../gnumach-1-branch-Xen-branch/ipc/mach_msg.c:1367 mach_call_call /home/tschwinge/tmp/gnumach/gnumach-1-branch-Xen-branch.build/../gnumach-1-branch-Xen-branch/i386/i386/locore.S:1083
raw_write_blk (channel=0x80829d8, data=0x8082a40, block=524272, count=8, buf=0x80a0a60) at ../../../git/lib/ext2fs/unix_io.c:272 272 actual = write(data->dev, buf, size); (gdb) print size $4 = 32768 (gdb) bt #0 raw_write_blk (channel=0x80829d8, data=0x8082a40, block=524272, count=8, buf=0x80a0a60) at ../../../git/lib/ext2fs/unix_io.c:272 #1 0x080635fc in unix_write_blk64 (channel=0x80829d8, block=524272, count=8, buf=0x80a0a60) at ../../../git/lib/ext2fs/unix_io.c:673 #2 0x0806373c in unix_write_blk (channel=0x80829d8, block=524272, count=8, buf=0x80a0a60) at ../../../git/lib/ext2fs/unix_io.c:705 #3 0x0805e87d in ext2fs_zero_blocks (fs=0x8082940, blk=524272, num=16, ret_blk=0x15ffb1c, ret_count=0x0) at ../../../git/lib/ext2fs/mkjournal.c:182 #4 0x0804ec56 in main (argc=131072, argv=0x80000) at ../../git/misc/mke2fs.c:2032
<tschwinge> I had a look at the code, but unfortunately don't really know how this data transfers between Xen and the domU work. <tschwinge> Well, I know how it roughly works, but not the implementation deatils. <youpi> well here it's not about the xen/domU transfers <youpi> it's about copying data to align it <youpi> i.e. when offset is not aligned, I need to copy it <tschwinge> Yes- <youpi> I was lazy, just implemented it for things smaller than a page <youpi> it just needs to be extended into copying several pages <tschwinge> youpi: Hmm, do we need to copy all the data to shift away the offset or is there a better way? <youpi> the blkbackend needs data to be sector-aligned <youpi> just aligning on a page makes offset computation simpler <youpi> as it's rare that's not a problem <tschwinge> And a sector is the usual 512 bytes there, I assume? <tschwinge> But then we do need to copy all of it? <youpi> let me check <youpi> the sector is the granularity you can't go below <youpi> sector is the sector_size reported by the backend <youpi> but for sector_number and first/last_sect it's 512 <youpi> yes, that's weird