From: Darrick J. Wong <djwong@kernel.org>
Date: Mon, 23 Sep 2024 20:42:55 +0000 (-0700)
Subject: xfs: enable realtime reflink
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=refs%2Fheads%2Frealtime-reflink-rebase;p=users%2Fhch%2Fxfs.git

xfs: enable realtime reflink

Enable reflink for realtime devices, sort of.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 86c4361dfd42..f352d70f82c8 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1822,3 +1822,28 @@ out:
 	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 3bfd7ab9e114..cc4e92278279 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 b47b44797836..f7b75a8c5e22 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
@@ -1287,7 +1288,8 @@ xfs_growfs_rt(
 	error = -EOPNOTSUPP;
 	if ((xfs_has_rmapbt(mp) || xfs_has_quota(mp)) && !xfs_has_rtgroups(mp))
 		goto out_unlock;
-	if (xfs_has_reflink(mp))
+	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 461c6a02d0d5..21300ca4c7bd 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1756,14 +1756,23 @@ xfs_fs_fill_super(
 "EXPERIMENTAL metadata directory feature in use. Use at your own risk!");
 
 	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;
 		}
 
-		if (xfs_globals.always_cow) {
+		/*
+		 * always-cow mode is not supported on filesystems with rt
+		 * extent sizes larger than a single block because we'd have
+		 * to perform write-around for unaligned writes because remap
+		 * requests must be aligned to an rt extent.
+		 */
+		if (xfs_globals.always_cow &&
+		    (!xfs_has_realtime(mp) || mp->m_sb.sb_rextsize == 1)) {
 			xfs_info(mp, "using DEBUG-only always_cow mode.");
 			mp->m_always_cow = true;
 		}