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From: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
To: linux-xfs@vger.kernel.org, linux-nvdimm@lists.01.org,
	darrick.wong@oracle.com
Cc: qi.fuli@fujitsu.com, gujx@cn.fujitsu.com, rgoldwyn@suse.de,
	david@fromorbit.com, linux-kernel@vger.kernel.org,
	Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: [RFC PATCH 1/7] dax: Introduce dax_copy_edges() for COW.
Date: Wed, 31 Jul 2019 19:49:29 +0800
Message-ID: <20190731114935.11030-2-ruansy.fnst@cn.fujitsu.com> (raw)
In-Reply-To: <20190731114935.11030-1-ruansy.fnst@cn.fujitsu.com>

To copy source data to destance address before write.  Change
dax_iomap_pfn() to return the address as well in order to use it for
performing a memcpy in case the type is IOMAP_COW.

dax_copy_edges() is a helper functions performs a copy from one part of
the device to another for data not page aligned.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
---
 fs/dax.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 52 insertions(+), 4 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 88b93796855e..450baafe2ea4 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -984,7 +984,7 @@ static sector_t dax_iomap_sector(struct iomap *iomap, loff_t pos)
 }
 
 static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
-			 pfn_t *pfnp)
+			 pfn_t *pfnp, void **addr)
 {
 	const sector_t sector = dax_iomap_sector(iomap, pos);
 	pgoff_t pgoff;
@@ -996,11 +996,13 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
 		return rc;
 	id = dax_read_lock();
 	length = dax_direct_access(iomap->dax_dev, pgoff, PHYS_PFN(size),
-				   NULL, pfnp);
+				   addr, pfnp);
 	if (length < 0) {
 		rc = length;
 		goto out;
 	}
+	if (!pfnp)
+		goto out_check_addr;
 	rc = -EINVAL;
 	if (PFN_PHYS(length) < size)
 		goto out;
@@ -1010,6 +1012,12 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
 	if (length > 1 && !pfn_t_devmap(*pfnp))
 		goto out;
 	rc = 0;
+
+out_check_addr:
+	if (!addr)
+		goto out;
+	if (!*addr)
+		rc = -EFAULT;
 out:
 	dax_read_unlock(id);
 	return rc;
@@ -1084,6 +1092,46 @@ int __dax_zero_page_range(struct block_device *bdev,
 }
 EXPORT_SYMBOL_GPL(__dax_zero_page_range);
 
+/*
+ * dax_copy_edges - Copies the part of the pages not included in
+ * 		    the write, but required for CoW because
+ * 		    offset/offset+length are not page aligned.
+ */
+static int dax_copy_edges(struct inode *inode, loff_t pos, loff_t length,
+			  struct iomap *srcmap, void *daddr)
+{
+	unsigned offset = pos & (PAGE_SIZE - 1);
+	loff_t end = pos + length;
+	loff_t pg_end = round_up(end, PAGE_SIZE);
+	void *saddr = 0;
+	int ret = 0;
+
+	ret = dax_iomap_pfn(srcmap, pos, length, NULL, &saddr);
+	if (ret)
+		return ret;
+	/*
+	 * Copy the first part of the page
+	 * Note: we pass offset as length
+	 */
+	if (offset) {
+		if (saddr)
+			ret = memcpy_mcsafe(daddr, saddr, offset);
+		else
+			memset(daddr, 0, offset);
+	}
+
+	/* Copy the last part of the range */
+	if (end < pg_end) {
+		if (saddr)
+			ret = memcpy_mcsafe(daddr + offset + length,
+			       saddr + offset + length,	pg_end - end);
+		else
+			memset(daddr + offset + length, 0,
+					pg_end - end);
+	}
+	return ret;
+}
+
 static loff_t
 dax_iomap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		struct iomap *iomap, struct iomap *srcmap)
@@ -1338,7 +1386,7 @@ static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
 			major = VM_FAULT_MAJOR;
 		}
-		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn);
+		error = dax_iomap_pfn(&iomap, pos, PAGE_SIZE, &pfn, NULL);
 		if (error < 0)
 			goto error_finish_iomap;
 
@@ -1555,7 +1603,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 
 	switch (iomap.type) {
 	case IOMAP_MAPPED:
-		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn);
+		error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn, NULL);
 		if (error < 0)
 			goto finish_iomap;
 
-- 
2.17.0



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Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-31 11:49 [RFC PATCH 0/7] xfs: add reflink & dedupe support for fsdax Shiyang Ruan
2019-07-31 11:49 ` Shiyang Ruan [this message]
2019-07-31 11:49 ` [RFC PATCH 2/7] dax: copy data before write Shiyang Ruan
2019-07-31 11:49 ` [RFC PATCH 3/7] dax: replace mmap entry in case of CoW Shiyang Ruan
2019-07-31 11:49 ` [RFC PATCH 4/7] fs: dedup file range to use a compare function Shiyang Ruan
2019-07-31 11:49 ` [RFC PATCH 5/7] dax: memcpy before zeroing range Shiyang Ruan
2019-07-31 11:49 ` [RFC PATCH 6/7] xfs: Add COW handle for fsdax Shiyang Ruan
2019-07-31 11:49 ` [RFC PATCH 7/7] xfs: Add dedupe support " Shiyang Ruan
2019-07-31 20:33 ` [RFC PATCH 0/7] xfs: add reflink & " Goldwyn Rodrigues
2019-08-01  1:37   ` Shiyang Ruan
2019-08-05  0:21     ` Dave Chinner
2019-10-09  6:31 ` Christoph Hellwig
2019-10-09 17:11   ` Darrick J. Wong
2019-10-10  7:30     ` Dave Chinner

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