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From: Vivek Goyal <vgoyal@redhat.com>
To: linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org,
	hch@infradead.org, dan.j.williams@intel.com
Cc: dm-devel@redhat.com, vishal.l.verma@intel.com, vgoyal@redhat.com
Subject: [PATCH v3 3/7] dax, pmem: Add a dax operation zero_page_range
Date: Fri,  7 Feb 2020 15:26:48 -0500
Message-ID: <20200207202652.1439-4-vgoyal@redhat.com> (raw)
In-Reply-To: <20200207202652.1439-1-vgoyal@redhat.com>

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 | 15 +++++++++++++++
 include/linux/dax.h   |  3 +++
 3 files changed, 37 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 281fe04d25fd..0def7dc8e487 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -299,6 +299,20 @@ 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)
+{
+	int rc;
+	struct pmem_device *pmem = dax_get_private(dax_dev);
+	struct page *page = ZERO_PAGE(0);
+
+	rc = pmem_do_write(pmem, page, 0, offset, len);
+	if (rc > 0)
+		return -EIO;
+
+	return 0;
+}
+
 static long pmem_dax_direct_access(struct dax_device *dax_dev,
 		pgoff_t pgoff, long nr_pages, void **kaddr, pfn_t *pfn)
 {
@@ -330,6 +344,7 @@ 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


  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-07 20:26 [PATCH v3 0/7] dax,pmem: Provide a dax operation to zero range of memory Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 1/7] pmem: Add functions for reading/writing page to/from pmem Vivek Goyal
2020-02-17 13:21   ` Christoph Hellwig
2020-02-17 18:04     ` Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 2/7] pmem: Enable pmem_do_write() to deal with arbitrary ranges Vivek Goyal
2020-02-17 13:23   ` Christoph Hellwig
2020-02-17 14:59     ` Vivek Goyal
2020-02-07 20:26 ` Vivek Goyal [this message]
2020-02-17 13:26   ` [PATCH v3 3/7] dax, pmem: Add a dax operation zero_page_range Christoph Hellwig
2020-02-17 18:08     ` Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 4/7] s390,dcssblk,dax: Add dax zero_page_range operation to dcssblk driver Vivek Goyal
2020-02-10 20:53   ` Gerald Schaefer
2020-02-11 15:11     ` Vivek Goyal
2020-02-11 15:49       ` Gerald Schaefer
2020-02-07 20:26 ` [PATCH v3 5/7] dm,dax: Add dax zero_page_range operation Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 6/7] dax,iomap: Start using dax native zero_page_range() Vivek Goyal
2020-02-17 13:26   ` Christoph Hellwig
2020-02-07 20:26 ` [PATCH v3 7/7] dax,iomap: Add helper dax_iomap_zero() to zero a range Vivek Goyal
2020-02-17 13:27   ` Christoph Hellwig
2020-02-14 12:57 ` [PATCH v3 0/7] dax,pmem: Provide a dax operation to zero range of memory Vivek Goyal

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