[PATCH v5 7/7] fs/xfs: Add dax dedupe support

[Shiyang Ruan]

Introduce xfs_mmaplock_two_inodes_and_break_dax_layout() for dax files
who are going to be deduped.  After that, call compare range function
only when files are both DAX or not.

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
 fs/xfs/xfs_file.c    |  2 +-
 fs/xfs/xfs_inode.c   | 66 +++++++++++++++++++++++++++++++++++++++++++-
 fs/xfs/xfs_inode.h   |  1 +
 fs/xfs/xfs_reflink.c |  4 +--
 4 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 38d8eca05aee..bd5002d38df4 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -823,7 +823,7 @@ xfs_wait_dax_page(
 	xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
 }
 
-static int
+int
 xfs_break_dax_layouts(
 	struct inode		*inode,
 	bool			*retry)
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 0369eb22c1bb..0774b6e2b940 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3711,6 +3711,64 @@ xfs_iolock_two_inodes_and_break_layout(
 	return 0;
 }
 
+static int
+xfs_mmaplock_two_inodes_and_break_dax_layout(
+	struct inode		*src,
+	struct inode		*dest)
+{
+	int			error, attempts = 0;
+	bool			retry;
+	struct xfs_inode	*ip0, *ip1;
+	struct page		*page;
+	struct xfs_log_item	*lp;
+
+	if (src > dest)
+		swap(src, dest);
+	ip0 = XFS_I(src);
+	ip1 = XFS_I(dest);
+
+again:
+	retry = false;
+	/* Lock the first inode */
+	xfs_ilock(ip0, XFS_MMAPLOCK_EXCL);
+	error = xfs_break_dax_layouts(src, &retry);
+	if (error || retry) {
+		xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL);
+		goto again;
+	}
+
+	if (src == dest)
+		return 0;
+
+	/* Nested lock the second inode */
+	lp = &ip0->i_itemp->ili_item;
+	if (lp && test_bit(XFS_LI_IN_AIL, &lp->li_flags)) {
+		if (!xfs_ilock_nowait(ip1,
+		    xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1))) {
+			xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL);
+			if ((++attempts % 5) == 0)
+				delay(1); /* Don't just spin the CPU */
+			goto again;
+		}
+	} else
+		xfs_ilock(ip1, xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1));
+	/*
+	 * We cannot use xfs_break_dax_layouts() directly here because it may
+	 * need to unlock & lock the XFS_MMAPLOCK_EXCL which is not suitable
+	 * for this nested lock case.
+	 */
+	page = dax_layout_busy_page(dest->i_mapping);
+	if (page) {
+		if (page_ref_count(page) != 1) {
+			xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
+			xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL);
+			goto again;
+		}
+	}
+
+	return 0;
+}
+
 /*
  * Lock two inodes so that userspace cannot initiate I/O via file syscalls or
  * mmap activity.
@@ -3721,10 +3779,16 @@ xfs_ilock2_io_mmap(
 	struct xfs_inode	*ip2)
 {
 	int			ret;
+	struct inode		*ino1 = VFS_I(ip1);
+	struct inode		*ino2 = VFS_I(ip2);
 
-	ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
+	ret = xfs_iolock_two_inodes_and_break_layout(ino1, ino2);
 	if (ret)
 		return ret;
+
+	if (IS_DAX(ino1) && IS_DAX(ino2))
+		return xfs_mmaplock_two_inodes_and_break_dax_layout(ino1, ino2);
+
 	if (ip1 == ip2)
 		xfs_ilock(ip1, XFS_MMAPLOCK_EXCL);
 	else
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index ca826cfba91c..2d0b344fb100 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -457,6 +457,7 @@ enum xfs_prealloc_flags {
 
 int	xfs_update_prealloc_flags(struct xfs_inode *ip,
 				  enum xfs_prealloc_flags flags);
+int	xfs_break_dax_layouts(struct inode *inode, bool *retry);
 int	xfs_break_layouts(struct inode *inode, uint *iolock,
 		enum layout_break_reason reason);
 
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 9a780948dbd0..ff308304c5cd 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1324,8 +1324,8 @@ xfs_reflink_remap_prep(
 	if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
 		goto out_unlock;
 
-	/* Don't share DAX file data for now. */
-	if (IS_DAX(inode_in) || IS_DAX(inode_out))
+	/* Don't share DAX file data with non-DAX file. */
+	if (IS_DAX(inode_in) != IS_DAX(inode_out))
 		goto out_unlock;
 
 	if (!IS_DAX(inode_in))
-- 
2.31.1