On Tue, Sep 18, 2018 at 07:48:04AM -0500, Eric Sandeen wrote:
> Not only that, but it must have told us that it had a /physical/ 512 sector.
> If it had even said physical/logical 4096/512, we would have chosen 4096.
Right, just after asking I discovered that the advertised
physical_block_size changes after attaching dm-writecache:
Before:
# dmsetup ls
foo-main (253:3)
foo-fast (253:4)
# cat /sys/block/dm-3/queue/physical_block_size
512
# cat /sys/block/dm-4/queue/physical_block_size
4096
After:
# dmsetup ls
foo-main_wcorig (253:4)
foo-main (253:5)
foo-fast (253:3)
# cat /sys/block/dm-3/queue/physical_block_size
4096
# cat /sys/block/dm-5/queue/physical_block_size
4096
> What does please check blockdev --getpbsz --getss /dev/$FOO say at mkfs time?
Before:
# blockdev --getpbsz --getss /dev/foo/main
512
512
After:
# blockdev --getpbsz --getss /dev/foo/main
4096
4096
> > Yes, it does, but mkfs should also fail when it tries to write 512
> > byte sectors to a 4k device, too.
By default it uses the 4k sectors in that case:
# mkfs.xfs -f /dev/foo/main
meta-data=/dev/foo/main isize=512 agcount=4, agsize=13056 blks
= sectsz=4096 attr=2, projid32bit=1
= crc=1 finobt=0, sparse=0
data = bsize=4096 blocks=52224, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=1605, version=2
= sectsz=4096 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
But you are correct if I request 512 on a 4k device:
# mkfs.xfs -f -s size=512 /dev/foo/main
illegal sector size 512; hw sector is 4096
> > I'm betting that the underlying device advertised a logical/physical
> > sector size of 512 bytes to mkfs, and then adding pmem as the cache
> > device changed the logical volume from a 512 byte sector device to a
> > hard 4k sector device.
Yes
I've been dealing with this by just using -s size=4096.
