[PATCH v4 0/7] dax/pmem: Provide a dax operation to zero range of memory

[PATCH v4 0/7] dax/pmem: Provide a dax operation to zero range of memory

[Vivek Goyal]

Hi,

This is V4 of patches. These patches are also available at.

https://github.com/rhvgoyal/linux/commits/dax-zero-range-v4

Changes since V3.

- Rebased patches on top of 5.6-rc1
- Took care of some of the comments from Christoph.
- Captured some Reviewed-by tags in some of the patches.  

Previous version of patches are here.
v3:
https://lore.kernel.org/linux-fsdevel/20200214125717.GA18654@redhat.com/T/#t
v2:
https://lore.kernel.org/linux-fsdevel/20200203200029.4592-1-vgoyal@redhat.com/
v1:
https://lore.kernel.org/linux-fsdevel/20200123165249.GA7664@redhat.com/

Thanks
Vivek

Vivek Goyal (7):
  pmem: Add functions for reading/writing page to/from pmem
  pmem: Enable pmem_do_write() to deal with arbitrary ranges
  dax, pmem: Add a dax operation zero_page_range
  s390,dcssblk,dax: Add dax zero_page_range operation to dcssblk driver
  dm,dax: Add dax zero_page_range operation
  dax,iomap: Start using dax native zero_page_range()
  dax,iomap: Add helper dax_iomap_zero() to zero a range

 drivers/dax/super.c           |  19 ++++++
 drivers/md/dm-linear.c        |  21 +++++++
 drivers/md/dm-log-writes.c    |  19 ++++++
 drivers/md/dm-stripe.c        |  26 ++++++++
 drivers/md/dm.c               |  31 +++++++++
 drivers/nvdimm/pmem.c         | 115 +++++++++++++++++++++++-----------
 drivers/s390/block/dcssblk.c  |  17 +++++
 fs/dax.c                      |  53 ++++------------
 fs/iomap/buffered-io.c        |   9 +--
 include/linux/dax.h           |  20 ++----
 include/linux/device-mapper.h |   3 +
 11 files changed, 233 insertions(+), 100 deletions(-)

-- 
2.20.1

[PATCH v4 1/7] pmem: Add functions for reading/writing page to/from pmem

[Vivek Goyal]

This splits pmem_do_bvec() into pmem_do_read() and pmem_do_write().
pmem_do_write() will be used by pmem zero_page_range() as well. Hence
sharing the same code.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 drivers/nvdimm/pmem.c | 86 +++++++++++++++++++++++++------------------
 1 file changed, 50 insertions(+), 36 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 4eae441f86c9..075b11682192 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -136,9 +136,25 @@ static blk_status_t read_pmem(struct page *page, unsigned int off,
 	return BLK_STS_OK;
 }
 
-static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
-			unsigned int len, unsigned int off, unsigned int op,
-			sector_t sector)
+static blk_status_t pmem_do_read(struct pmem_device *pmem,
+			struct page *page, unsigned int page_off,
+			sector_t sector, unsigned int len)
+{
+	blk_status_t rc;
+	phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
+	void *pmem_addr = pmem->virt_addr + pmem_off;
+
+	if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
+		return BLK_STS_IOERR;
+
+	rc = read_pmem(page, page_off, pmem_addr, len);
+	flush_dcache_page(page);
+	return rc;
+}
+
+static blk_status_t pmem_do_write(struct pmem_device *pmem,
+			struct page *page, unsigned int page_off,
+			sector_t sector, unsigned int len)
 {
 	blk_status_t rc = BLK_STS_OK;
 	bool bad_pmem = false;
@@ -148,34 +164,25 @@ static blk_status_t pmem_do_bvec(struct pmem_device *pmem, struct page *page,
 	if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
 		bad_pmem = true;
 
-	if (!op_is_write(op)) {
-		if (unlikely(bad_pmem))
-			rc = BLK_STS_IOERR;
-		else {
-			rc = read_pmem(page, off, pmem_addr, len);
-			flush_dcache_page(page);
-		}
-	} else {
-		/*
-		 * Note that we write the data both before and after
-		 * clearing poison.  The write before clear poison
-		 * handles situations where the latest written data is
-		 * preserved and the clear poison operation simply marks
-		 * the address range as valid without changing the data.
-		 * In this case application software can assume that an
-		 * interrupted write will either return the new good
-		 * data or an error.
-		 *
-		 * However, if pmem_clear_poison() leaves the data in an
-		 * indeterminate state we need to perform the write
-		 * after clear poison.
-		 */
-		flush_dcache_page(page);
-		write_pmem(pmem_addr, page, off, len);
-		if (unlikely(bad_pmem)) {
-			rc = pmem_clear_poison(pmem, pmem_off, len);
-			write_pmem(pmem_addr, page, off, len);
-		}
+	/*
+	 * Note that we write the data both before and after
+	 * clearing poison.  The write before clear poison
+	 * handles situations where the latest written data is
+	 * preserved and the clear poison operation simply marks
+	 * the address range as valid without changing the data.
+	 * In this case application software can assume that an
+	 * interrupted write will either return the new good
+	 * data or an error.
+	 *
+	 * However, if pmem_clear_poison() leaves the data in an
+	 * indeterminate state we need to perform the write
+	 * after clear poison.
+	 */
+	flush_dcache_page(page);
+	write_pmem(pmem_addr, page, page_off, len);
+	if (unlikely(bad_pmem)) {
+		rc = pmem_clear_poison(pmem, pmem_off, len);
+		write_pmem(pmem_addr, page, page_off, len);
 	}
 
 	return rc;
@@ -197,8 +204,12 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
-		rc = pmem_do_bvec(pmem, bvec.bv_page, bvec.bv_len,
-				bvec.bv_offset, bio_op(bio), iter.bi_sector);
+		if (op_is_write(bio_op(bio)))
+			rc = pmem_do_write(pmem, bvec.bv_page, bvec.bv_offset,
+				iter.bi_sector, bvec.bv_len);
+		else
+			rc = pmem_do_read(pmem, bvec.bv_page, bvec.bv_offset,
+				iter.bi_sector, bvec.bv_len);
 		if (rc) {
 			bio->bi_status = rc;
 			break;
@@ -223,9 +234,12 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
 	struct pmem_device *pmem = bdev->bd_queue->queuedata;
 	blk_status_t rc;
 
-	rc = pmem_do_bvec(pmem, page, hpage_nr_pages(page) * PAGE_SIZE,
-			  0, op, sector);
-
+	if (op_is_write(op))
+		rc = pmem_do_write(pmem, page, 0, sector,
+				   hpage_nr_pages(page) * PAGE_SIZE);
+	else
+		rc = pmem_do_read(pmem, page, 0, sector,
+				   hpage_nr_pages(page) * PAGE_SIZE);
 	/*
 	 * The ->rw_page interface is subtle and tricky.  The core
 	 * retries on any error, so we can only invoke page_endio() in
-- 
2.20.1

Re: [dm-devel] [PATCH v4 1/7] pmem: Add functions for reading/writing page to/from pmem

[Christoph Hellwig]

On Mon, Feb 17, 2020 at 01:16:47PM -0500, Vivek Goyal wrote:
> This splits pmem_do_bvec() into pmem_do_read() and pmem_do_write().
> pmem_do_write() will be used by pmem zero_page_range() as well. Hence
> sharing the same code.
> 
> Suggested-by: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH v4 2/7] pmem: Enable pmem_do_write() to deal with arbitrary ranges

[Vivek Goyal]

Currently pmem_do_write() is written with assumption that all I/O is
sector aligned. Soon I want to use this function in zero_page_range()
where range passed in does not have to be sector aligned.

Modify this function to be able to deal with an arbitrary range. Which
is specified by pmem_off and len.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 drivers/nvdimm/pmem.c | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 075b11682192..fae8f67da9de 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -154,15 +154,23 @@ static blk_status_t pmem_do_read(struct pmem_device *pmem,
 
 static blk_status_t pmem_do_write(struct pmem_device *pmem,
 			struct page *page, unsigned int page_off,
-			sector_t sector, unsigned int len)
+			u64 pmem_off, unsigned int len)
 {
 	blk_status_t rc = BLK_STS_OK;
 	bool bad_pmem = false;
-	phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
-	void *pmem_addr = pmem->virt_addr + pmem_off;
-
-	if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
-		bad_pmem = true;
+	phys_addr_t pmem_real_off = pmem_off + pmem->data_offset;
+	void *pmem_addr = pmem->virt_addr + pmem_real_off;
+	sector_t sector_start, sector_end;
+	unsigned nr_sectors;
+
+	sector_start = DIV_ROUND_UP(pmem_off, SECTOR_SIZE);
+	sector_end = (pmem_off + len) >> SECTOR_SHIFT;
+	if (sector_end > sector_start) {
+		nr_sectors = sector_end - sector_start;
+		if (is_bad_pmem(&pmem->bb, sector_start,
+				nr_sectors << SECTOR_SHIFT))
+			bad_pmem = true;
+	}
 
 	/*
 	 * Note that we write the data both before and after
@@ -181,7 +189,13 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem,
 	flush_dcache_page(page);
 	write_pmem(pmem_addr, page, page_off, len);
 	if (unlikely(bad_pmem)) {
-		rc = pmem_clear_poison(pmem, pmem_off, len);
+		/*
+		 * Pass sector aligned offset and length. That seems
+		 * to work as of now. Other finer grained alignment
+		 * cases can be addressed later if need be.
+		 */
+		rc = pmem_clear_poison(pmem, ALIGN(pmem_real_off, SECTOR_SIZE),
+				       nr_sectors << SECTOR_SHIFT);
 		write_pmem(pmem_addr, page, page_off, len);
 	}
 
@@ -206,7 +220,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	bio_for_each_segment(bvec, bio, iter) {
 		if (op_is_write(bio_op(bio)))
 			rc = pmem_do_write(pmem, bvec.bv_page, bvec.bv_offset,
-				iter.bi_sector, bvec.bv_len);
+				iter.bi_sector << SECTOR_SHIFT, bvec.bv_len);
 		else
 			rc = pmem_do_read(pmem, bvec.bv_page, bvec.bv_offset,
 				iter.bi_sector, bvec.bv_len);
@@ -235,7 +249,7 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
 	blk_status_t rc;
 
 	if (op_is_write(op))
-		rc = pmem_do_write(pmem, page, 0, sector,
+		rc = pmem_do_write(pmem, page, 0, sector << SECTOR_SHIFT,
 				   hpage_nr_pages(page) * PAGE_SIZE);
 	else
 		rc = pmem_do_read(pmem, page, 0, sector,
-- 
2.20.1

Re: [dm-devel] [PATCH v4 2/7] pmem: Enable pmem_do_write() to deal with arbitrary ranges

[Christoph Hellwig]

On Mon, Feb 17, 2020 at 01:16:48PM -0500, Vivek Goyal wrote:
> Currently pmem_do_write() is written with assumption that all I/O is
> sector aligned. Soon I want to use this function in zero_page_range()
> where range passed in does not have to be sector aligned.
> 
> Modify this function to be able to deal with an arbitrary range. Which
> is specified by pmem_off and len.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
>  drivers/nvdimm/pmem.c | 32 +++++++++++++++++++++++---------
>  1 file changed, 23 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 075b11682192..fae8f67da9de 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -154,15 +154,23 @@ static blk_status_t pmem_do_read(struct pmem_device *pmem,
>  
>  static blk_status_t pmem_do_write(struct pmem_device *pmem,
>  			struct page *page, unsigned int page_off,
> -			sector_t sector, unsigned int len)
> +			u64 pmem_off, unsigned int len)
>  {
>  	blk_status_t rc = BLK_STS_OK;
>  	bool bad_pmem = false;
> -	phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
> -	void *pmem_addr = pmem->virt_addr + pmem_off;
> -
> -	if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
> -		bad_pmem = true;
> +	phys_addr_t pmem_real_off = pmem_off + pmem->data_offset;
> +	void *pmem_addr = pmem->virt_addr + pmem_real_off;
> +	sector_t sector_start, sector_end;
> +	unsigned nr_sectors;
> +
> +	sector_start = DIV_ROUND_UP(pmem_off, SECTOR_SIZE);
> +	sector_end = (pmem_off + len) >> SECTOR_SHIFT;
> +	if (sector_end > sector_start) {
> +		nr_sectors = sector_end - sector_start;
> +		if (is_bad_pmem(&pmem->bb, sector_start,
> +				nr_sectors << SECTOR_SHIFT))
> +			bad_pmem = true;
> +	}
>  
>  	/*
>  	 * Note that we write the data both before and after
> @@ -181,7 +189,13 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem,
>  	flush_dcache_page(page);
>  	write_pmem(pmem_addr, page, page_off, len);
>  	if (unlikely(bad_pmem)) {
> -		rc = pmem_clear_poison(pmem, pmem_off, len);
> +		/*
> +		 * Pass sector aligned offset and length. That seems
> +		 * to work as of now. Other finer grained alignment
> +		 * cases can be addressed later if need be.
> +		 */
> +		rc = pmem_clear_poison(pmem, ALIGN(pmem_real_off, SECTOR_SIZE),
> +				       nr_sectors << SECTOR_SHIFT);
>  		write_pmem(pmem_addr, page, page_off, len);

I'm still scared about the as of now commnet.  If the interface to
clearing poison is page aligned I think we should document that in the
actual pmem_clear_poison function, and make that take the unaligned
offset.  I also think we want some feedback from Dan or other what the
official interface is instead of "seems to work".

Re: [dm-devel] [PATCH v4 2/7] pmem: Enable pmem_do_write() to deal with arbitrary ranges

[Vivek Goyal]

On Tue, Feb 18, 2020 at 09:09:28AM -0800, Christoph Hellwig wrote:
> On Mon, Feb 17, 2020 at 01:16:48PM -0500, Vivek Goyal wrote:
> > Currently pmem_do_write() is written with assumption that all I/O is
> > sector aligned. Soon I want to use this function in zero_page_range()
> > where range passed in does not have to be sector aligned.
> > 
> > Modify this function to be able to deal with an arbitrary range. Which
> > is specified by pmem_off and len.
> > 
> > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> > ---
> >  drivers/nvdimm/pmem.c | 32 +++++++++++++++++++++++---------
> >  1 file changed, 23 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> > index 075b11682192..fae8f67da9de 100644
> > --- a/drivers/nvdimm/pmem.c
> > +++ b/drivers/nvdimm/pmem.c
> > @@ -154,15 +154,23 @@ static blk_status_t pmem_do_read(struct pmem_device *pmem,
> >  
> >  static blk_status_t pmem_do_write(struct pmem_device *pmem,
> >  			struct page *page, unsigned int page_off,
> > -			sector_t sector, unsigned int len)
> > +			u64 pmem_off, unsigned int len)
> >  {
> >  	blk_status_t rc = BLK_STS_OK;
> >  	bool bad_pmem = false;
> > -	phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
> > -	void *pmem_addr = pmem->virt_addr + pmem_off;
> > -
> > -	if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
> > -		bad_pmem = true;
> > +	phys_addr_t pmem_real_off = pmem_off + pmem->data_offset;
> > +	void *pmem_addr = pmem->virt_addr + pmem_real_off;
> > +	sector_t sector_start, sector_end;
> > +	unsigned nr_sectors;
> > +
> > +	sector_start = DIV_ROUND_UP(pmem_off, SECTOR_SIZE);
> > +	sector_end = (pmem_off + len) >> SECTOR_SHIFT;
> > +	if (sector_end > sector_start) {
> > +		nr_sectors = sector_end - sector_start;
> > +		if (is_bad_pmem(&pmem->bb, sector_start,
> > +				nr_sectors << SECTOR_SHIFT))
> > +			bad_pmem = true;
> > +	}
> >  
> >  	/*
> >  	 * Note that we write the data both before and after
> > @@ -181,7 +189,13 @@ static blk_status_t pmem_do_write(struct pmem_device *pmem,
> >  	flush_dcache_page(page);
> >  	write_pmem(pmem_addr, page, page_off, len);
> >  	if (unlikely(bad_pmem)) {
> > -		rc = pmem_clear_poison(pmem, pmem_off, len);
> > +		/*
> > +		 * Pass sector aligned offset and length. That seems
> > +		 * to work as of now. Other finer grained alignment
> > +		 * cases can be addressed later if need be.
> > +		 */
> > +		rc = pmem_clear_poison(pmem, ALIGN(pmem_real_off, SECTOR_SIZE),
> > +				       nr_sectors << SECTOR_SHIFT);
> >  		write_pmem(pmem_addr, page, page_off, len);
> 
> I'm still scared about the as of now commnet.  If the interface to
> clearing poison is page aligned I think we should document that in the
> actual pmem_clear_poison function, and make that take the unaligned
> offset.  I also think we want some feedback from Dan or other what the
> official interface is instead of "seems to work".

Ok, I am adding one more patch to series and enabling pmem_clear_poison()
to accept arbitrary offset and length and let it align offset and length
to sector boundary. Keeping it in a separate patch so that Dan can have
a close look at it and make sure I am doing things correctly.

Here is the new patch. I will post the V5 soon with this new patch.

Thanks
Vivek


Subject: drivers/pmem: Allow pmem_clear_poison() to accept arbitrary offset and len

Currently pmem_clear_poison() expects offset and len to be sector aligned.
Atleast that seems to be the assumption with which code has been written.
It is called only from pmem_do_bvec() which is called only from pmem_rw_page()
and pmem_make_request() which will only passe sector aligned offset and len.

Soon we want use this function from dax_zero_page_range() code path which
can try to zero arbitrary range of memory with-in a page. So update this
function to assume that offset and length can be arbitrary and do the
necessary alignments as needed.

nvdimm_clear_poison() seems to assume offset and len to be aligned to
clear_err_unit boundary. But this is currently internal detail and is
not exported for others to use. So for now, continue to align offset and
length to SECTOR_SIZE boundary. Improving it further and to align it
to clear_err_unit boundary is a TODO item for future.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 drivers/nvdimm/pmem.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 075b11682192..e72959203253 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -74,14 +74,28 @@ static blk_status_t pmem_clear_poison(struct pmem_device *pmem,
 	sector_t sector;
 	long cleared;
 	blk_status_t rc = BLK_STS_OK;
+	phys_addr_t start_aligned, end_aligned;
+	unsigned int len_aligned;
 
-	sector = (offset - pmem->data_offset) / 512;
+	/*
+	 * Callers can pass arbitrary offset and len. But nvdimm_clear_poison()
+	 * expects memory offset and length to meet certain alignment
+	 * restrction (clear_err_unit). Currently nvdimm does not export
+	 * required alignment. So align offset and length to sector boundary
+	 * before passing it to nvdimm_clear_poison().
+	 */
+	start_aligned = ALIGN(offset, SECTOR_SIZE);
+	end_aligned = ALIGN_DOWN((offset + len), SECTOR_SIZE) - 1;
+	len_aligned = end_aligned - start_aligned + 1;
+
+	sector = (start_aligned - pmem->data_offset) / 512;
 
-	cleared = nvdimm_clear_poison(dev, pmem->phys_addr + offset, len);
-	if (cleared < len)
+	cleared = nvdimm_clear_poison(dev, pmem->phys_addr + start_aligned,
+				      len_aligned);
+	if (cleared < len_aligned)
 		rc = BLK_STS_IOERR;
 	if (cleared > 0 && cleared / 512) {
-		hwpoison_clear(pmem, pmem->phys_addr + offset, cleared);
+		hwpoison_clear(pmem, pmem->phys_addr + start_aligned, cleared);
 		cleared /= 512;
 		dev_dbg(dev, "%#llx clear %ld sector%s\n",
 				(unsigned long long) sector, cleared,
-- 
2.20.1

[PATCH v4 3/7] dax, pmem: Add a dax operation zero_page_range

[Vivek Goyal]

Add a dax operation zero_page_range, to zero a range of memory. This will
also clear any poison in the range being zeroed.

As of now, zeroing of up to one page is allowed in a single call. There
are no callers which are trying to zero more than a page in a single call.
Once we grow the callers which zero more than a page in single call, we
can add that support. Primary reason for not doing that yet is that this
will add little complexity in dm implementation where a range might be
spanning multiple underlying targets and one will have to split the range
into multiple sub ranges and call zero_page_range() on individual targets.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 drivers/dax/super.c   | 19 +++++++++++++++++++
 drivers/nvdimm/pmem.c | 11 +++++++++++
 include/linux/dax.h   |  3 +++
 3 files changed, 33 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 26a654dbc69a..31ee0b47b4ed 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -344,6 +344,25 @@ size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
 }
 EXPORT_SYMBOL_GPL(dax_copy_to_iter);
 
+int dax_zero_page_range(struct dax_device *dax_dev, u64 offset, size_t len)
+{
+	if (!dax_alive(dax_dev))
+		return -ENXIO;
+
+	if (!dax_dev->ops->zero_page_range)
+		return -EOPNOTSUPP;
+	/*
+	 * There are no callers that want to zero across a page boundary as of
+	 * now. Once users are there, this check can be removed after the
+	 * device mapper code has been updated to split ranges across targets.
+	 */
+	if (offset_in_page(offset) + len > PAGE_SIZE)
+		return -EIO;
+
+	return dax_dev->ops->zero_page_range(dax_dev, offset, len);
+}
+EXPORT_SYMBOL_GPL(dax_zero_page_range);
+
 #ifdef CONFIG_ARCH_HAS_PMEM_API
 void arch_wb_cache_pmem(void *addr, size_t size);
 void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index fae8f67da9de..44f660fa56ca 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -296,6 +296,16 @@ static const struct block_device_operations pmem_fops = {
 	.revalidate_disk =	nvdimm_revalidate_disk,
 };
 
+static int pmem_dax_zero_page_range(struct dax_device *dax_dev, u64 offset,
+				    size_t len)
+{
+	struct pmem_device *pmem = dax_get_private(dax_dev);
+	blk_status_t rc;
+
+	rc = pmem_do_write(pmem, ZERO_PAGE(0), 0, offset, len);
+	return blk_status_to_errno(rc);
+}
+
 static long pmem_dax_direct_access(struct dax_device *dax_dev,
 		pgoff_t pgoff, long nr_pages, void **kaddr, pfn_t *pfn)
 {
@@ -327,6 +337,7 @@ static const struct dax_operations pmem_dax_ops = {
 	.dax_supported = generic_fsdax_supported,
 	.copy_from_iter = pmem_copy_from_iter,
 	.copy_to_iter = pmem_copy_to_iter,
+	.zero_page_range = pmem_dax_zero_page_range,
 };
 
 static const struct attribute_group *pmem_attribute_groups[] = {
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 9bd8528bd305..a555f0aeb7bd 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -34,6 +34,8 @@ struct dax_operations {
 	/* copy_to_iter: required operation for fs-dax direct-i/o */
 	size_t (*copy_to_iter)(struct dax_device *, pgoff_t, void *, size_t,
 			struct iov_iter *);
+	/* zero_page_range: required operation. Zero range with-in a page  */
+	int (*zero_page_range)(struct dax_device *, u64, size_t);
 };
 
 extern struct attribute_group dax_attribute_group;
@@ -209,6 +211,7 @@ size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
 		size_t bytes, struct iov_iter *i);
 size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
 		size_t bytes, struct iov_iter *i);
+int dax_zero_page_range(struct dax_device *dax_dev, u64 offset, size_t len);
 void dax_flush(struct dax_device *dax_dev, void *addr, size_t size);
 
 ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
-- 
2.20.1

Re: [dm-devel] [PATCH v4 3/7] dax, pmem: Add a dax operation zero_page_range

[Christoph Hellwig]

> +static int pmem_dax_zero_page_range(struct dax_device *dax_dev, u64 offset,
> +				    size_t len)
> +{
> +	struct pmem_device *pmem = dax_get_private(dax_dev);
> +	blk_status_t rc;
> +
> +	rc = pmem_do_write(pmem, ZERO_PAGE(0), 0, offset, len);
> +	return blk_status_to_errno(rc);

No real need for the rc variable here.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH v4 4/7] s390,dcssblk,dax: Add dax zero_page_range operation to dcssblk driver

[Vivek Goyal]

Add dax operation zero_page_range for dcssblk driver.

CC: linux-s390@vger.kernel.org
Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 drivers/s390/block/dcssblk.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 63502ca537eb..331abab5d066 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -57,11 +57,28 @@ static size_t dcssblk_dax_copy_to_iter(struct dax_device *dax_dev,
 	return copy_to_iter(addr, bytes, i);
 }
 
+static int dcssblk_dax_zero_page_range(struct dax_device *dax_dev, u64 offset,
+				       size_t len)
+{
+	long rc;
+	void *kaddr;
+	pgoff_t pgoff = offset >> PAGE_SHIFT;
+	unsigned page_offset = offset_in_page(offset);
+
+	rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
+	if (rc < 0)
+		return rc;
+	memset(kaddr + page_offset, 0, len);
+	dax_flush(dax_dev, kaddr + page_offset, len);
+	return 0;
+}
+
 static const struct dax_operations dcssblk_dax_ops = {
 	.direct_access = dcssblk_dax_direct_access,
 	.dax_supported = generic_fsdax_supported,
 	.copy_from_iter = dcssblk_dax_copy_from_iter,
 	.copy_to_iter = dcssblk_dax_copy_to_iter,
+	.zero_page_range = dcssblk_dax_zero_page_range,
 };
 
 struct dcssblk_dev_info {
-- 
2.20.1

[PATCH v4 5/7] dm,dax: Add dax zero_page_range operation

[Vivek Goyal]

This patch adds support for dax zero_page_range operation to dm targets.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 drivers/md/dm-linear.c        | 21 +++++++++++++++++++++
 drivers/md/dm-log-writes.c    | 19 +++++++++++++++++++
 drivers/md/dm-stripe.c        | 26 ++++++++++++++++++++++++++
 drivers/md/dm.c               | 31 +++++++++++++++++++++++++++++++
 include/linux/device-mapper.h |  3 +++
 5 files changed, 100 insertions(+)

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 8d07fdf63a47..03f99e6ad372 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -201,10 +201,30 @@ static size_t linear_dax_copy_to_iter(struct dm_target *ti, pgoff_t pgoff,
 	return dax_copy_to_iter(dax_dev, pgoff, addr, bytes, i);
 }
 
+static int linear_dax_zero_page_range(struct dm_target *ti, u64 offset,
+				      size_t len)
+{
+	int ret;
+	struct linear_c *lc = ti->private;
+	struct block_device *bdev = lc->dev->bdev;
+	struct dax_device *dax_dev = lc->dev->dax_dev;
+	pgoff_t pgoff = offset >> PAGE_SHIFT;
+	unsigned page_offset = offset_in_page(offset);
+	sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
+
+	dev_sector = linear_map_sector(ti, sector);
+	ret = bdev_dax_pgoff(bdev, dev_sector, ALIGN(len, PAGE_SIZE), &pgoff);
+	if (ret)
+		return ret;
+	return dax_zero_page_range(dax_dev, (pgoff << PAGE_SHIFT) + page_offset,
+				   len);
+}
+
 #else
 #define linear_dax_direct_access NULL
 #define linear_dax_copy_from_iter NULL
 #define linear_dax_copy_to_iter NULL
+#define linear_dax_zero_page_range NULL
 #endif
 
 static struct target_type linear_target = {
@@ -226,6 +246,7 @@ static struct target_type linear_target = {
 	.direct_access = linear_dax_direct_access,
 	.dax_copy_from_iter = linear_dax_copy_from_iter,
 	.dax_copy_to_iter = linear_dax_copy_to_iter,
+	.dax_zero_page_range = linear_dax_zero_page_range,
 };
 
 int __init dm_linear_init(void)
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index 99721c76225d..f36ee223cb60 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -994,10 +994,28 @@ static size_t log_writes_dax_copy_to_iter(struct dm_target *ti,
 	return dax_copy_to_iter(lc->dev->dax_dev, pgoff, addr, bytes, i);
 }
 
+static int log_writes_dax_zero_page_range(struct dm_target *ti, u64 offset,
+					  size_t len)
+{
+	int ret;
+	struct log_writes_c *lc = ti->private;
+	pgoff_t pgoff = offset >> PAGE_SHIFT;
+	unsigned page_offset = offset_in_page(offset);
+	sector_t sector = pgoff * PAGE_SECTORS;
+
+	ret = bdev_dax_pgoff(lc->dev->bdev, sector, ALIGN(len, PAGE_SIZE),
+			     &pgoff);
+	if (ret)
+		return ret;
+	return dax_zero_page_range(lc->dev->dax_dev,
+				   (pgoff << PAGE_SHIFT) + page_offset, len);
+}
+
 #else
 #define log_writes_dax_direct_access NULL
 #define log_writes_dax_copy_from_iter NULL
 #define log_writes_dax_copy_to_iter NULL
+#define log_writes_dax_zero_page_range NULL
 #endif
 
 static struct target_type log_writes_target = {
@@ -1016,6 +1034,7 @@ static struct target_type log_writes_target = {
 	.direct_access = log_writes_dax_direct_access,
 	.dax_copy_from_iter = log_writes_dax_copy_from_iter,
 	.dax_copy_to_iter = log_writes_dax_copy_to_iter,
+	.dax_zero_page_range = log_writes_dax_zero_page_range,
 };
 
 static int __init dm_log_writes_init(void)
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 63bbcc20f49a..f5e17284c615 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -360,10 +360,35 @@ static size_t stripe_dax_copy_to_iter(struct dm_target *ti, pgoff_t pgoff,
 	return dax_copy_to_iter(dax_dev, pgoff, addr, bytes, i);
 }
 
+static int stripe_dax_zero_page_range(struct dm_target *ti, u64 offset,
+				      size_t len)
+{
+	int ret;
+	pgoff_t pgoff = offset >> PAGE_SHIFT;
+	unsigned page_offset = offset_in_page(offset);
+	sector_t dev_sector, sector = pgoff * PAGE_SECTORS;
+	struct stripe_c *sc = ti->private;
+	struct dax_device *dax_dev;
+	struct block_device *bdev;
+	uint32_t stripe;
+
+	stripe_map_sector(sc, sector, &stripe, &dev_sector);
+	dev_sector += sc->stripe[stripe].physical_start;
+	dax_dev = sc->stripe[stripe].dev->dax_dev;
+	bdev = sc->stripe[stripe].dev->bdev;
+
+	ret = bdev_dax_pgoff(bdev, dev_sector, ALIGN(len, PAGE_SIZE), &pgoff);
+	if (ret)
+		return ret;
+	return dax_zero_page_range(dax_dev, (pgoff << PAGE_SHIFT) + page_offset,
+				   len);
+}
+
 #else
 #define stripe_dax_direct_access NULL
 #define stripe_dax_copy_from_iter NULL
 #define stripe_dax_copy_to_iter NULL
+#define stripe_dax_zero_page_range NULL
 #endif
 
 /*
@@ -486,6 +511,7 @@ static struct target_type stripe_target = {
 	.direct_access = stripe_dax_direct_access,
 	.dax_copy_from_iter = stripe_dax_copy_from_iter,
 	.dax_copy_to_iter = stripe_dax_copy_to_iter,
+	.dax_zero_page_range = stripe_dax_zero_page_range,
 };
 
 int __init dm_stripe_init(void)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index b89f07ee2eff..c87cabdf7f18 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1198,6 +1198,36 @@ static size_t dm_dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff,
 	return ret;
 }
 
+static int dm_dax_zero_page_range(struct dax_device *dax_dev, u64 offset,
+				  size_t len)
+{
+	struct mapped_device *md = dax_get_private(dax_dev);
+	pgoff_t pgoff = offset >> PAGE_SHIFT;
+	sector_t sector = pgoff * PAGE_SECTORS;
+	struct dm_target *ti;
+	int ret = -EIO;
+	int srcu_idx;
+
+	ti = dm_dax_get_live_target(md, sector, &srcu_idx);
+
+	if (!ti)
+		goto out;
+	if (WARN_ON(!ti->type->dax_zero_page_range)) {
+		/*
+		 * ->zero_page_range() is mandatory dax operation. If we are
+		 *  here, something is wrong.
+		 */
+		dm_put_live_table(md, srcu_idx);
+		goto out;
+	}
+	ret = ti->type->dax_zero_page_range(ti, offset, len);
+
+ out:
+	dm_put_live_table(md, srcu_idx);
+
+	return ret;
+}
+
 /*
  * A target may call dm_accept_partial_bio only from the map routine.  It is
  * allowed for all bio types except REQ_PREFLUSH, REQ_OP_ZONE_RESET,
@@ -3199,6 +3229,7 @@ static const struct dax_operations dm_dax_ops = {
 	.dax_supported = dm_dax_supported,
 	.copy_from_iter = dm_dax_copy_from_iter,
 	.copy_to_iter = dm_dax_copy_to_iter,
+	.zero_page_range = dm_dax_zero_page_range,
 };
 
 /*
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 475668c69dbc..b4ef5b07be74 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -141,6 +141,8 @@ typedef long (*dm_dax_direct_access_fn) (struct dm_target *ti, pgoff_t pgoff,
 		long nr_pages, void **kaddr, pfn_t *pfn);
 typedef size_t (*dm_dax_copy_iter_fn)(struct dm_target *ti, pgoff_t pgoff,
 		void *addr, size_t bytes, struct iov_iter *i);
+typedef int (*dm_dax_zero_page_range_fn)(struct dm_target *ti, u64 offset,
+		size_t len);
 #define PAGE_SECTORS (PAGE_SIZE / 512)
 
 void dm_error(const char *message);
@@ -195,6 +197,7 @@ struct target_type {
 	dm_dax_direct_access_fn direct_access;
 	dm_dax_copy_iter_fn dax_copy_from_iter;
 	dm_dax_copy_iter_fn dax_copy_to_iter;
+	dm_dax_zero_page_range_fn dax_zero_page_range;
 
 	/* For internal device-mapper use. */
 	struct list_head list;
-- 
2.20.1

[PATCH v4 6/7] dax,iomap: Start using dax native zero_page_range()

[Vivek Goyal]

Get rid of calling block device interface for zeroing in iomap dax
zeroing path and use dax native zeroing interface instead.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/dax.c | 45 +++++++++------------------------------------
 1 file changed, 9 insertions(+), 36 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 1f1f0201cad1..6757e12b86b2 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1044,48 +1044,21 @@ static vm_fault_t dax_load_hole(struct xa_state *xas,
 	return ret;
 }
 
-static bool dax_range_is_aligned(struct block_device *bdev,
-				 unsigned int offset, unsigned int length)
-{
-	unsigned short sector_size = bdev_logical_block_size(bdev);
-
-	if (!IS_ALIGNED(offset, sector_size))
-		return false;
-	if (!IS_ALIGNED(length, sector_size))
-		return false;
-
-	return true;
-}
-
 int __dax_zero_page_range(struct block_device *bdev,
 		struct dax_device *dax_dev, sector_t sector,
 		unsigned int offset, unsigned int size)
 {
-	if (dax_range_is_aligned(bdev, offset, size)) {
-		sector_t start_sector = sector + (offset >> 9);
-
-		return blkdev_issue_zeroout(bdev, start_sector,
-				size >> 9, GFP_NOFS, 0);
-	} else {
-		pgoff_t pgoff;
-		long rc, id;
-		void *kaddr;
+	pgoff_t pgoff;
+	long rc, id;
 
-		rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
-		if (rc)
-			return rc;
+	rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
+	if (rc)
+		return rc;
 
-		id = dax_read_lock();
-		rc = dax_direct_access(dax_dev, pgoff, 1, &kaddr, NULL);
-		if (rc < 0) {
-			dax_read_unlock(id);
-			return rc;
-		}
-		memset(kaddr + offset, 0, size);
-		dax_flush(dax_dev, kaddr + offset, size);
-		dax_read_unlock(id);
-	}
-	return 0;
+	id = dax_read_lock();
+	rc = dax_zero_page_range(dax_dev, (pgoff << PAGE_SHIFT) + offset, size);
+	dax_read_unlock(id);
+	return rc;
 }
 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 
-- 
2.20.1

[PATCH v4 7/7] dax,iomap: Add helper dax_iomap_zero() to zero a range

[Vivek Goyal]

Add a helper dax_ioamp_zero() to zero a range. This patch basically
merges __dax_zero_page_range() and iomap_dax_zero().

Suggested-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 fs/dax.c               | 12 ++++++------
 fs/iomap/buffered-io.c |  9 +--------
 include/linux/dax.h    | 17 +++--------------
 3 files changed, 10 insertions(+), 28 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 6757e12b86b2..f6c4788ba764 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1044,23 +1044,23 @@ static vm_fault_t dax_load_hole(struct xa_state *xas,
 	return ret;
 }
 
-int __dax_zero_page_range(struct block_device *bdev,
-		struct dax_device *dax_dev, sector_t sector,
-		unsigned int offset, unsigned int size)
+int dax_iomap_zero(loff_t pos, unsigned offset, unsigned size,
+		   struct iomap *iomap)
 {
 	pgoff_t pgoff;
 	long rc, id;
+	sector_t sector = iomap_sector(iomap, pos & PAGE_MASK);
 
-	rc = bdev_dax_pgoff(bdev, sector, PAGE_SIZE, &pgoff);
+	rc = bdev_dax_pgoff(iomap->bdev, sector, PAGE_SIZE, &pgoff);
 	if (rc)
 		return rc;
 
 	id = dax_read_lock();
-	rc = dax_zero_page_range(dax_dev, (pgoff << PAGE_SHIFT) + offset, size);
+	rc = dax_zero_page_range(iomap->dax_dev, (pgoff << PAGE_SHIFT) + offset,
+				 size);
 	dax_read_unlock(id);
 	return rc;
 }
-EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 7c84c4c027c4..6f750da545e5 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -974,13 +974,6 @@ static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
 	return iomap_write_end(inode, pos, bytes, bytes, page, iomap, srcmap);
 }
 
-static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
-		struct iomap *iomap)
-{
-	return __dax_zero_page_range(iomap->bdev, iomap->dax_dev,
-			iomap_sector(iomap, pos & PAGE_MASK), offset, bytes);
-}
-
 static loff_t
 iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
 		void *data, struct iomap *iomap, struct iomap *srcmap)
@@ -1000,7 +993,7 @@ iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
 		bytes = min_t(loff_t, PAGE_SIZE - offset, count);
 
 		if (IS_DAX(inode))
-			status = iomap_dax_zero(pos, offset, bytes, iomap);
+			status = dax_iomap_zero(pos, offset, bytes, iomap);
 		else
 			status = iomap_zero(inode, pos, offset, bytes, iomap,
 					srcmap);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index a555f0aeb7bd..31d0e6fc3023 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -13,6 +13,7 @@
 typedef unsigned long dax_entry_t;
 
 struct iomap_ops;
+struct iomap;
 struct dax_device;
 struct dax_operations {
 	/*
@@ -223,20 +224,8 @@ vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
 				      pgoff_t index);
-
-#ifdef CONFIG_FS_DAX
-int __dax_zero_page_range(struct block_device *bdev,
-		struct dax_device *dax_dev, sector_t sector,
-		unsigned int offset, unsigned int length);
-#else
-static inline int __dax_zero_page_range(struct block_device *bdev,
-		struct dax_device *dax_dev, sector_t sector,
-		unsigned int offset, unsigned int length)
-{
-	return -ENXIO;
-}
-#endif
-
+int dax_iomap_zero(loff_t pos, unsigned offset, unsigned size,
+			struct iomap *iomap);
 static inline bool dax_mapping(struct address_space *mapping)
 {
 	return mapping->host && IS_DAX(mapping->host);
-- 
2.20.1