> > > >
> > > > This patch adds 'DAXDEV_SYNC' flag which is set
> > > > for nd_region doing synchronous flush. This later
> > > > is used to disable MAP_SYNC functionality for
> > > > ext4 & xfs filesystem for devices don't support
> > > > synchronous flush.
> > > >
> > > > Signed-off-by: Pankaj Gupta <[email protected]>
> > > > ---
> > > > drivers/dax/bus.c | 2 +-
> > > > drivers/dax/super.c | 13 ++++++++++++-
> > > > drivers/md/dm.c | 3 ++-
> > > > drivers/nvdimm/pmem.c | 5 ++++-
> > > > drivers/nvdimm/region_devs.c | 7 +++++++
> > > > include/linux/dax.h | 8 ++++++--
> > > > include/linux/libnvdimm.h | 1 +
> > > > 7 files changed, 33 insertions(+), 6 deletions(-)
> > > [..]
> > > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > > > index 043f0761e4a0..ee007b75d9fd 100644
> > > > --- a/drivers/md/dm.c
> > > > +++ b/drivers/md/dm.c
> > > > @@ -1969,7 +1969,8 @@ static struct mapped_device *alloc_dev(int minor)
> > > > sprintf(md->disk->disk_name, "dm-%d", minor);
> > > >
> > > > if (IS_ENABLED(CONFIG_DAX_DRIVER)) {
> > > > - dax_dev = alloc_dax(md, md->disk->disk_name,
> > > > &dm_dax_ops);
> > > > + dax_dev = alloc_dax(md, md->disk->disk_name,
> > > > &dm_dax_ops,
> > > > +
> > > > DAXDEV_F_SYNC);
> > >
> > > Apologies for not realizing this until now, but this is broken.
> > > Imaging a device-mapper configuration composed of both 'async'
> > > virtio-pmem and 'sync' pmem. The 'sync' flag needs to be unified
> > > across all members. I would change this argument to '0' and then
> > > arrange for it to be set at dm_table_supports_dax() time after
> > > validating that all components support synchronous dax.
> >
> > o.k. Need to set 'DAXDEV_F_SYNC' flag after verifying all the target
> > components support synchronous DAX.
> >
> > Just a question, If device mapper configuration have composed of both
> > virtio-pmem or pmem devices, we want to configure device mapper for async
> > flush?
>
> If it's composed of both then, yes, it needs to be async flush at the
> device-mapper level. Otherwise MAP_SYNC will succeed and fail to
> trigger fsync on the host file when necessary for the virtio-pmem
> backed portion of the device-mapper device.
o.k. Agree.
Thanks you,
Pankaj
>
>
Hi Dan,
While testing device mapper with DAX, I faced a bug with the commit:
commit ad428cdb525a97d15c0349fdc80f3d58befb50df
Author: Dan Williams <[email protected]>
Date: Wed Feb 20 21:12:50 2019 -0800
When I reverted the condition to old code[1] it worked for me. I
am thinking when we map two different devices (e.g with device mapper), will
start & end pfn still point to same pgmap? Or there is something else which
I am missing here.
Note: I tested only EXT4.
[1]
- if (pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX)
+ end_pgmap = get_dev_pagemap(pfn_t_to_pfn(end_pfn), NULL);
+ if (pgmap && pgmap == end_pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX
+ && pfn_t_to_page(pfn)->pgmap == pgmap
+ && pfn_t_to_page(end_pfn)->pgmap == pgmap
+ && pfn_t_to_pfn(pfn) == PHYS_PFN(__pa(kaddr))
+ && pfn_t_to_pfn(end_pfn) == PHYS_PFN(__pa(end_kaddr)))
dax_enabled = true;
put_dev_pagemap(pgmap);
Thanks,
Pankaj