[PATCH 43/43] xfs: enable realtime reflink

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Enable reflink for realtime devices, as long as the realtime allocation
unit is a single fsblock.

Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
 fs/xfs/xfs_reflink.c |   25 +++++++++++++++++++++++++
 fs/xfs/xfs_reflink.h |    2 ++
 fs/xfs/xfs_rtalloc.c |    7 +++++--
 fs/xfs/xfs_super.c   |    6 ++++--
 4 files changed, 36 insertions(+), 4 deletions(-)


diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index d9b33e22c17669..59f7fc16eb8093 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1822,3 +1822,28 @@ xfs_reflink_unshare(
 	trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
 	return error;
 }
+
+/*
+ * Can we use reflink with this realtime extent size?  Note that we don't check
+ * for rblocks > 0 here because this can be called as part of attaching a new
+ * rt section.
+ */
+bool
+xfs_reflink_supports_rextsize(
+	struct xfs_mount	*mp,
+	unsigned int		rextsize)
+{
+	/* reflink on the realtime device requires rtgroups */
+	if (!xfs_has_rtgroups(mp))
+	       return false;
+
+	/*
+	 * Reflink doesn't support rt extent size larger than a single fsblock
+	 * because we would have to perform CoW-around for unaligned write
+	 * requests to guarantee that we always remap entire rt extents.
+	 */
+	if (rextsize != 1)
+		return false;
+
+	return true;
+}
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index 3bfd7ab9e1148a..cc4e92278279b6 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -62,4 +62,6 @@ extern int xfs_reflink_remap_blocks(struct xfs_inode *src, loff_t pos_in,
 extern int xfs_reflink_update_dest(struct xfs_inode *dest, xfs_off_t newlen,
 		xfs_extlen_t cowextsize, unsigned int remap_flags);
 
+bool xfs_reflink_supports_rextsize(struct xfs_mount *mp, unsigned int rextsize);
+
 #endif /* __XFS_REFLINK_H */
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 7135a6717a9e11..d8e6d073d64dc9 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -32,6 +32,7 @@
 #include "xfs_error.h"
 #include "xfs_trace.h"
 #include "xfs_rtrefcount_btree.h"
+#include "xfs_reflink.h"
 
 /*
  * Return whether there are any free extents in the size range given
@@ -1292,8 +1293,10 @@ xfs_growfs_rt(
 			goto out_unlock;
 		if (xfs_has_quota(mp))
 			goto out_unlock;
-	}
-	if (xfs_has_reflink(mp))
+		if (xfs_has_reflink(mp))
+			goto out_unlock;
+	} else if (xfs_has_reflink(mp) &&
+		   !xfs_reflink_supports_rextsize(mp, in->extsize))
 		goto out_unlock;
 
 	error = xfs_sb_validate_fsb_count(&mp->m_sb, in->newblocks);
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index ecd5a9f444d862..7c3f996cd39e81 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1754,9 +1754,11 @@ xfs_fs_fill_super(
 		xfs_warn_experimental(mp, XFS_EXPERIMENTAL_METADIR);
 
 	if (xfs_has_reflink(mp)) {
-		if (mp->m_sb.sb_rblocks) {
+		if (xfs_has_realtime(mp) &&
+		    !xfs_reflink_supports_rextsize(mp, mp->m_sb.sb_rextsize)) {
 			xfs_alert(mp,
-	"reflink not compatible with realtime device!");
+	"reflink not compatible with realtime extent size %u!",
+					mp->m_sb.sb_rextsize);
 			error = -EINVAL;
 			goto out_filestream_unmount;
 		}