On Thu, Jan 23, 2020 at 11:52:49AM -0500, Vivek Goyal wrote: > Hi, > > This is an RFC patch to provide a dax operation to zero a range of memory. > It will also clear poison in the process. This is primarily compile tested > patch. I don't have real hardware to test the poison logic. I am posting > this to figure out if this is the right direction or not. > > Motivation from this patch comes from Christoph's feedback that he will > rather prefer a dax way to zero a range instead of relying on having to > call blkdev_issue_zeroout() in __dax_zero_page_range(). > > https://lkml.org/lkml/2019/8/26/361 > > My motivation for this change is virtiofs DAX support. There we use DAX > but we don't have a block device. So any dax code which has the assumption > that there is always a block device associated is a problem. So this > is more of a cleanup of one of the places where dax has this dependency > on block device and if we add a dax operation for zeroing a range, it > can help with not having to call blkdev_issue_zeroout() in dax path. > > I have yet to take care of stacked block drivers (dm/md). > > Current poison clearing logic is primarily written with assumption that > I/O is sector aligned. With this new method, this assumption is broken > and one can pass any range of memory to zero. I have fixed few places > in existing logic to be able to handle an arbitrary start/end. I am > not sure are there other dependencies which might need fixing or > prohibit us from providing this method. > > Any feedback or comment is welcome. > > Thanks > Vivek > > --- > drivers/dax/super.c | 13 +++++++++ > drivers/nvdimm/pmem.c | 67 ++++++++++++++++++++++++++++++++++++++++++-------- > fs/dax.c | 39 ++++++++--------------------- > include/linux/dax.h | 3 ++ > 4 files changed, 85 insertions(+), 37 deletions(-) > > Index: rhvgoyal-linux/drivers/nvdimm/pmem.c > =================================================================== > --- rhvgoyal-linux.orig/drivers/nvdimm/pmem.c 2020-01-23 11:32:11.075139183 -0500 > +++ rhvgoyal-linux/drivers/nvdimm/pmem.c 2020-01-23 11:32:28.660139183 -0500 > @@ -52,8 +52,8 @@ static void hwpoison_clear(struct pmem_d > if (is_vmalloc_addr(pmem->virt_addr)) > return; > > - pfn_start = PHYS_PFN(phys); > - pfn_end = pfn_start + PHYS_PFN(len); > + pfn_start = PFN_UP(phys); > + pfn_end = PFN_DOWN(phys + len); > for (pfn = pfn_start; pfn < pfn_end; pfn++) { > struct page *page = pfn_to_page(pfn); > This change looks unrelated to the rest. > + sector_end = ALIGN_DOWN((offset - pmem->data_offset + len), 512)/512; > + nr_sectors = sector_end - sector_start; > > cleared = nvdimm_clear_poison(dev, pmem->phys_addr + offset, len); > if (cleared < len) > rc = BLK_STS_IOERR; > - if (cleared > 0 && cleared / 512) { > + if (cleared > 0 && nr_sectors > 0) { > hwpoison_clear(pmem, pmem->phys_addr + offset, cleared); > - cleared /= 512; > - dev_dbg(dev, "%#llx clear %ld sector%s\n", > - (unsigned long long) sector, cleared, > - cleared > 1 ? "s" : ""); > - badblocks_clear(&pmem->bb, sector, cleared); > + dev_dbg(dev, "%#llx clear %d sector%s\n", > + (unsigned long long) sector_start, nr_sectors, > + nr_sectors > 1 ? "s" : ""); > + badblocks_clear(&pmem->bb, sector_start, nr_sectors); > if (pmem->bb_state) > sysfs_notify_dirent(pmem->bb_state); > } As does this one? > int __dax_zero_page_range(struct block_device *bdev, > struct dax_device *dax_dev, sector_t sector, > unsigned int offset, unsigned int size) > { > + pgoff_t pgoff; > + long rc, id; > > + rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff); > + if (rc) > + return rc; > + > + id = dax_read_lock(); > + rc = dax_zero_page_range(dax_dev, pgoff, offset, size); > + if (rc == -EOPNOTSUPP) { > void *kaddr; > > + /* If driver does not implement zero page range, fallback */ I think we'll want to restructure this a bit. First make the new method mandatory, and just provide a generic_dax_zero_page_range or similar for the non-pmem instances. Then __dax_zero_page_range and iomap_dax_zero should merge, and maybe eventually iomap_zero_range_actor and iomap_zero_range should be split into a pagecache and DAX variant, lifting the IS_DAXD check into the callers.
