[PATCH 03/14] xfs: create a log incompat flag for atomic file mapping exchanges

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Create a log incompat flag so that we only attempt to process file
mapping exchange log items if the filesystem supports it, and a geometry
flag to advertise support if it's present or could be present.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/libxfs/xfs_format.h |   13 +++++++++++++
 fs/xfs/libxfs/xfs_fs.h     |    3 +++
 fs/xfs/libxfs/xfs_sb.c     |    3 +++
 fs/xfs/xfs_exchrange.c     |   31 +++++++++++++++++++++++++++++++
 fs/xfs/xfs_exchrange.h     |    2 ++
 5 files changed, 52 insertions(+)


diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 2b2f9050fbfbb..753adde56a2d0 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -391,6 +391,12 @@ xfs_sb_has_incompat_feature(
 }
 
 #define XFS_SB_FEAT_INCOMPAT_LOG_XATTRS   (1 << 0)	/* Delayed Attributes */
+
+/*
+ * Log contains file mapping exchange log intent items which are not otherwise
+ * protected by an INCOMPAT/RO_COMPAT feature flag.
+ */
+#define XFS_SB_FEAT_INCOMPAT_LOG_EXCHMAPS (1 << 1)
 #define XFS_SB_FEAT_INCOMPAT_LOG_ALL \
 	(XFS_SB_FEAT_INCOMPAT_LOG_XATTRS)
 #define XFS_SB_FEAT_INCOMPAT_LOG_UNKNOWN	~XFS_SB_FEAT_INCOMPAT_LOG_ALL
@@ -423,6 +429,13 @@ static inline bool xfs_sb_version_haslogxattrs(struct xfs_sb *sbp)
 		 XFS_SB_FEAT_INCOMPAT_LOG_XATTRS);
 }
 
+static inline bool xfs_sb_version_haslogexchmaps(struct xfs_sb *sbp)
+{
+	return xfs_sb_is_v5(sbp) &&
+		(sbp->sb_features_log_incompat &
+		 XFS_SB_FEAT_INCOMPAT_LOG_EXCHMAPS);
+}
+
 static inline bool
 xfs_is_quota_inode(struct xfs_sb *sbp, xfs_ino_t ino)
 {
diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index 8a1e30cf4dc88..ea07fb7b89722 100644
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -240,6 +240,9 @@ typedef struct xfs_fsop_resblks {
 #define XFS_FSOP_GEOM_FLAGS_INOBTCNT	(1 << 22) /* inobt btree counter */
 #define XFS_FSOP_GEOM_FLAGS_NREXT64	(1 << 23) /* large extent counters */
 
+/* file range exchange available to userspace */
+#define XFS_FSOP_GEOM_FLAGS_EXCHANGE_RANGE	(1 << 24)
+
 /*
  * Minimum and maximum sizes need for growth checks.
  *
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index d991eec054368..c2d86faeee61b 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -26,6 +26,7 @@
 #include "xfs_health.h"
 #include "xfs_ag.h"
 #include "xfs_rtbitmap.h"
+#include "xfs_exchrange.h"
 
 /*
  * Physical superblock buffer manipulations. Shared with libxfs in userspace.
@@ -1258,6 +1259,8 @@ xfs_fs_geometry(
 	}
 	if (xfs_has_large_extent_counts(mp))
 		geo->flags |= XFS_FSOP_GEOM_FLAGS_NREXT64;
+	if (xfs_exchrange_possible(mp))
+		geo->flags |= XFS_FSOP_GEOM_FLAGS_EXCHANGE_RANGE;
 	geo->rtsectsize = sbp->sb_blocksize;
 	geo->dirblocksize = xfs_dir2_dirblock_bytes(sbp);
 
diff --git a/fs/xfs/xfs_exchrange.c b/fs/xfs/xfs_exchrange.c
index a575e26ae1a58..620cf1eb7464b 100644
--- a/fs/xfs/xfs_exchrange.c
+++ b/fs/xfs/xfs_exchrange.c
@@ -15,6 +15,37 @@
 #include "xfs_exchrange.h"
 #include <linux/fsnotify.h>
 
+/*
+ * If the filesystem has relatively new features enabled, we're willing to
+ * upgrade the filesystem to have the EXCHMAPS log incompat feature.
+ * Technically we could do this with any V5 filesystem, but let's not deal
+ * with really old kernels.
+ */
+static inline bool
+xfs_exchrange_upgradeable(
+	struct xfs_mount	*mp)
+{
+	return xfs_has_bigtime(mp) || xfs_has_large_extent_counts(mp);
+}
+
+/*
+ * Decide if we should advertise to userspace the potential for using file
+ * range exchanges on this filesystem.  This does not say anything about the
+ * actual readiness to start such an operation.
+ */
+bool
+xfs_exchrange_possible(
+	struct xfs_mount	*mp)
+{
+	/* Always possible when mapping exchange log intent items are enabled */
+	if (xfs_sb_version_haslogexchmaps(&mp->m_sb))
+		return true;
+
+	/* Can we upgrade the fs to have the log intent item? */
+	return xfs_exchrange_upgradeable(mp) &&
+	       xfs_can_add_incompat_log_features(mp, false);
+}
+
 /*
  * Generic code for exchanging ranges of two files via XFS_IOC_EXCHANGE_RANGE.
  * This part deals with struct file objects and byte ranges and does not deal
diff --git a/fs/xfs/xfs_exchrange.h b/fs/xfs/xfs_exchrange.h
index 923c386cb9756..a6e35942d9442 100644
--- a/fs/xfs/xfs_exchrange.h
+++ b/fs/xfs/xfs_exchrange.h
@@ -6,6 +6,8 @@
 #ifndef __XFS_EXCHRANGE_H__
 #define __XFS_EXCHRANGE_H__
 
+bool xfs_exchrange_possible(struct xfs_mount *mp);
+
 /* Update the mtime/cmtime of file1 and file2 */
 #define __XFS_EXCHANGE_RANGE_UPD_CMTIME1	(1ULL << 63)
 #define __XFS_EXCHANGE_RANGE_UPD_CMTIME2	(1ULL << 62)