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From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: linux-fsdevel@vger.kernel.org
Cc: linux-btrfs@vger.kernel.org, darrick.wong@oracle.com, hch@lst.de,
	linux-xfs@vger.kernel.org, Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: [PATCH 02/15] iomap: Read page from srcmap if IOMAP_F_COW is set
Date: Thu,  5 Sep 2019 10:06:37 -0500	[thread overview]
Message-ID: <20190905150650.21089-3-rgoldwyn@suse.de> (raw)
In-Reply-To: <20190905150650.21089-1-rgoldwyn@suse.de>

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

In case of a IOMAP_F_COW, read a page from the srcmap before
performing a write on the page.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/iomap/buffered-io.c | 30 +++++++++++++++++++++---------
 include/linux/iomap.h  |  3 +++
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index f27756c0b31c..560459df75e4 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -581,7 +581,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
 
 static int
 iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
-		struct page **pagep, struct iomap *iomap)
+		struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
 {
 	const struct iomap_page_ops *page_ops = iomap->page_ops;
 	pgoff_t index = pos >> PAGE_SHIFT;
@@ -605,12 +605,24 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
 		goto out_no_page;
 	}
 
-	if (iomap->type == IOMAP_INLINE)
+	if (iomap->type == IOMAP_INLINE) {
 		iomap_read_inline_data(inode, page, iomap);
-	else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
+	} else if (iomap->flags & IOMAP_F_COW) {
+		if (WARN_ON_ONCE(iomap->flags & IOMAP_F_BUFFER_HEAD)) {
+			status = -EIO;
+			goto out_no_page;
+		}
+		if (WARN_ON_ONCE(srcmap->type == IOMAP_HOLE &&
+				 srcmap->addr != IOMAP_NULL_ADDR)) {
+			status = -EIO;
+			goto out_no_page;
+		}
+		status = __iomap_write_begin(inode, pos, len, page, srcmap);
+	} else if (iomap->flags & IOMAP_F_BUFFER_HEAD) {
 		status = __block_write_begin_int(page, pos, len, NULL, iomap);
-	else
+	} else {
 		status = __iomap_write_begin(inode, pos, len, page, iomap);
+	}
 
 	if (unlikely(status))
 		goto out_unlock;
@@ -772,7 +784,7 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		}
 
 		status = iomap_write_begin(inode, pos, bytes, flags, &page,
-				iomap);
+				iomap, srcmap);
 		if (unlikely(status))
 			break;
 
@@ -871,7 +883,7 @@ iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 			return PTR_ERR(rpage);
 
 		status = iomap_write_begin(inode, pos, bytes,
-					   AOP_FLAG_NOFS, &page, iomap);
+					   AOP_FLAG_NOFS, &page, iomap, srcmap);
 		put_page(rpage);
 		if (unlikely(status))
 			return status;
@@ -917,13 +929,13 @@ iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
 EXPORT_SYMBOL_GPL(iomap_file_dirty);
 
 static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
-		unsigned bytes, struct iomap *iomap)
+		unsigned bytes, struct iomap *iomap, struct iomap *srcmap)
 {
 	struct page *page;
 	int status;
 
 	status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page,
-				   iomap);
+				   iomap, srcmap);
 	if (status)
 		return status;
 
@@ -961,7 +973,7 @@ iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
 		if (IS_DAX(inode))
 			status = iomap_dax_zero(pos, offset, bytes, iomap);
 		else
-			status = iomap_zero(inode, pos, offset, bytes, iomap);
+			status = iomap_zero(inode, pos, offset, bytes, iomap, srcmap);
 		if (status < 0)
 			return status;
 
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 9782a79dde59..7fdb09925740 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -44,6 +44,9 @@ struct vm_fault;
 #define IOMAP_F_MERGED		0x10	/* contains multiple blocks/extents */
 #define IOMAP_F_SHARED		0x20	/* block shared with another file */
 
+/* Flags for CoW */
+#define IOMAP_F_COW		0x100	/* copy from srcmap before write */
+
 /*
  * Flags from 0x1000 up are for file system specific usage:
  */
-- 
2.16.4


  parent reply	other threads:[~2019-09-05 15:07 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-05 15:06 [PATCH v4 0/15] CoW support for iomap Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 01/15] iomap: Use a srcmap for a read-modify-write I/O Goldwyn Rodrigues
2019-09-05 23:23   ` Darrick J. Wong
2019-09-05 15:06 ` Goldwyn Rodrigues [this message]
2019-09-05 16:37   ` [PATCH 02/15] iomap: Read page from srcmap if IOMAP_F_COW is set Christoph Hellwig
2019-09-05 20:28     ` Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 03/15] btrfs: Eliminate PagePrivate for btrfs data pages Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 04/15] btrfs: Add a simple buffered iomap write Goldwyn Rodrigues
2019-09-05 16:23   ` Christoph Hellwig
2019-09-05 20:42     ` Goldwyn Rodrigues
2019-09-06  5:54       ` Christoph Hellwig
2019-09-05 15:06 ` [PATCH 05/15] btrfs: Add CoW in iomap based writes Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 06/15] btrfs: remove buffered write code made unnecessary Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 07/15] fs: Export generic_file_buffered_read() Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 08/15] btrfs: basic direct read operation Goldwyn Rodrigues
2019-09-05 16:25   ` Christoph Hellwig
2019-09-05 15:06 ` [PATCH 09/15] btrfs: Carve out btrfs_get_extent_map_write() out of btrfs_get_blocks_write() Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 10/15] btrfs: Rename __endio_write_update_ordered() to btrfs_update_ordered_extent() Goldwyn Rodrigues
2019-09-05 15:06 ` [PATCH 11/15] iomap: use a function pointer for dio submits Goldwyn Rodrigues
2019-09-05 16:27   ` Christoph Hellwig
2019-09-05 23:24     ` Darrick J. Wong
2019-09-05 15:06 ` [PATCH 12/15] btrfs: Use iomap_dio_rw for performing direct I/O writes Goldwyn Rodrigues
2019-09-05 16:31   ` Christoph Hellwig
2019-09-05 15:06 ` [PATCH 13/15] btrfs: Remove btrfs_dio_data and __btrfs_direct_write Goldwyn Rodrigues
2019-09-05 16:32   ` Christoph Hellwig
2019-09-05 15:06 ` [PATCH 14/15] btrfs: update inode size during bio completion Goldwyn Rodrigues
2019-09-05 16:33   ` Christoph Hellwig
2019-09-05 15:06 ` [PATCH 15/15] xfs: Use the new iomap infrastructure for CoW Goldwyn Rodrigues
2019-09-06 16:55   ` Christoph Hellwig
2019-09-06 23:28     ` Dave Chinner

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