[PATCH 14/13] xfs: make XFS_IOC_COMMIT_RANGE freshness data opaque

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

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

To head off bikeshedding about the fields in xfs_commit_range, let's
make it an opaque u64 array and require the userspace program to call
a third ioctl to sample the freshness data for us.  If we ever converge
on a definition for i_version then we can use that; for now we'll just
use mtime/ctime like the old swapext ioctl.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_fs.h |   13 +++--------
 fs/xfs/xfs_exchrange.c |   15 ++++++++++++
 fs/xfs/xfs_exchrange.h |    1 +
 fs/xfs/xfs_ioctl.c     |   58 +++++++++++++++++++++++++++++++++++++++++++-----
 4 files changed, 72 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index 01b3553adfc55..4019a78ee3ea5 100644
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -860,14 +860,8 @@ struct xfs_commit_range {
 
 	__u64		flags;		/* see XFS_EXCHRANGE_* below */
 
-	/* file2 metadata for freshness checks */
-	__u64		file2_ino;	/* inode number */
-	__s64		file2_mtime;	/* modification time */
-	__s64		file2_ctime;	/* change time */
-	__s32		file2_mtime_nsec; /* mod time, nsec */
-	__s32		file2_ctime_nsec; /* change time, nsec */
-
-	__u64		pad;		/* must be zeroes */
+	/* opaque file2 metadata for freshness checks */
+	__u64		file2_freshness[5];
 };
 
 /*
@@ -973,7 +967,8 @@ struct xfs_commit_range {
 #define XFS_IOC_BULKSTAT	     _IOR ('X', 127, struct xfs_bulkstat_req)
 #define XFS_IOC_INUMBERS	     _IOR ('X', 128, struct xfs_inumbers_req)
 #define XFS_IOC_EXCHANGE_RANGE	     _IOWR('X', 129, struct xfs_exch_range)
-#define XFS_IOC_COMMIT_RANGE	     _IOWR('X', 129, struct xfs_commit_range)
+#define XFS_IOC_START_COMMIT	     _IOWR('X', 130, struct xfs_commit_range)
+#define XFS_IOC_COMMIT_RANGE	     _IOWR('X', 131, struct xfs_commit_range)
 /*	XFS_IOC_GETFSUUID ---------- deprecated 140	 */
 
 
diff --git a/fs/xfs/xfs_exchrange.c b/fs/xfs/xfs_exchrange.c
index e55ae06f1a32c..dae855515c3c4 100644
--- a/fs/xfs/xfs_exchrange.c
+++ b/fs/xfs/xfs_exchrange.c
@@ -863,3 +863,18 @@ xfs_exchange_range(
 		fsnotify_modify(fxr->file2);
 	return 0;
 }
+
+/* Sample freshness data from fxr->file2 for a commit range operation. */
+void
+xfs_exchrange_freshness(
+	struct xfs_exchrange	*fxr)
+{
+	struct inode		*inode2 = file_inode(fxr->file2);
+	struct xfs_inode	*ip2 = XFS_I(inode2);
+
+	xfs_ilock(ip2, XFS_IOLOCK_SHARED | XFS_MMAPLOCK_SHARED | XFS_ILOCK_SHARED);
+	fxr->file2_ino = ip2->i_ino;
+	fxr->file2_ctime = inode_get_ctime(inode2);
+	fxr->file2_mtime = inode_get_mtime(inode2);
+	xfs_iunlock(ip2, XFS_IOLOCK_SHARED | XFS_MMAPLOCK_SHARED | XFS_ILOCK_SHARED);
+}
diff --git a/fs/xfs/xfs_exchrange.h b/fs/xfs/xfs_exchrange.h
index 2dd9ab7d76828..942283a7f75f5 100644
--- a/fs/xfs/xfs_exchrange.h
+++ b/fs/xfs/xfs_exchrange.h
@@ -36,6 +36,7 @@ struct xfs_exchrange {
 	struct timespec64	file2_ctime;
 };
 
+void xfs_exchrange_freshness(struct xfs_exchrange *fxr);
 int xfs_exchange_range(struct xfs_exchrange *fxr);
 
 /* XFS-specific parts of file exchanges */
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index ee26ac2028da1..1940da72a1da7 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -2402,6 +2402,47 @@ xfs_ioc_exchange_range(
 	return error;
 }
 
+/* Opaque freshness blob for XFS_IOC_COMMIT_RANGE */
+struct xfs_commit_range_fresh {
+	__u64		file2_ino;	/* inode number */
+	__s64		file2_mtime;	/* modification time */
+	__s64		file2_ctime;	/* change time */
+	__s32		file2_mtime_nsec; /* mod time, nsec */
+	__s32		file2_ctime_nsec; /* change time, nsec */
+	__u64		pad;		/* zero */
+};
+
+static long
+xfs_ioc_start_commit(
+	struct file			*file,
+	struct xfs_commit_range __user	*argp)
+{
+	struct xfs_exchrange		fxr = {
+		.file2			= file,
+	};
+	struct xfs_commit_range		args;
+	struct xfs_commit_range_fresh	*kern_f;
+	struct xfs_commit_range_fresh	__user *user_f;
+
+	BUILD_BUG_ON(sizeof(struct xfs_commit_range_fresh) !=
+		     sizeof(args.file2_freshness));
+
+	xfs_exchrange_freshness(&fxr);
+
+	kern_f = (struct xfs_commit_range_fresh *)&args.file2_freshness;
+	kern_f->file2_ino		= fxr.file2_ino;
+	kern_f->file2_mtime		= fxr.file2_mtime.tv_sec;
+	kern_f->file2_mtime_nsec	= fxr.file2_mtime.tv_nsec;
+	kern_f->file2_ctime		= fxr.file2_ctime.tv_sec;
+	kern_f->file2_ctime_nsec	= fxr.file2_ctime.tv_nsec;
+
+	user_f = (struct xfs_commit_range_fresh *)&argp->file2_freshness;
+	if (copy_to_user(user_f, kern_f, sizeof(*kern_f)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static long
 xfs_ioc_commit_range(
 	struct file			*file,
@@ -2411,12 +2452,15 @@ xfs_ioc_commit_range(
 		.file2			= file,
 	};
 	struct xfs_commit_range		args;
+	struct xfs_commit_range_fresh	*kern_f;
 	struct fd			file1;
 	int				error;
 
+	kern_f = (struct xfs_commit_range_fresh *)&args.file2_freshness;
+
 	if (copy_from_user(&args, argp, sizeof(args)))
 		return -EFAULT;
-	if (memchr_inv(&args.pad, 0, sizeof(args.pad)))
+	if (memchr_inv(&kern_f->pad, 0, sizeof(kern_f->pad)))
 		return -EINVAL;
 	if (args.flags & ~XFS_EXCHRANGE_ALL_FLAGS)
 		return -EINVAL;
@@ -2425,11 +2469,11 @@ xfs_ioc_commit_range(
 	fxr.file2_offset	= args.file2_offset;
 	fxr.length		= args.length;
 	fxr.flags		= args.flags | __XFS_EXCHRANGE_CHECK_FRESH2;
-	fxr.file2_ino		= args.file2_ino;
-	fxr.file2_mtime.tv_sec	= args.file2_mtime;
-	fxr.file2_mtime.tv_nsec	= args.file2_mtime_nsec;
-	fxr.file2_ctime.tv_sec	= args.file2_ctime;
-	fxr.file2_ctime.tv_nsec	= args.file2_ctime_nsec;
+	fxr.file2_ino		= kern_f->file2_ino;
+	fxr.file2_mtime.tv_sec	= kern_f->file2_mtime;
+	fxr.file2_mtime.tv_nsec	= kern_f->file2_mtime_nsec;
+	fxr.file2_ctime.tv_sec	= kern_f->file2_ctime;
+	fxr.file2_ctime.tv_nsec	= kern_f->file2_ctime_nsec;
 
 	file1 = fdget(args.file1_fd);
 	if (!file1.file)
@@ -2782,6 +2826,8 @@ xfs_file_ioctl(
 
 	case XFS_IOC_EXCHANGE_RANGE:
 		return xfs_ioc_exchange_range(filp, arg);
+	case XFS_IOC_START_COMMIT:
+		return xfs_ioc_start_commit(filp, arg);
 	case XFS_IOC_COMMIT_RANGE:
 		return xfs_ioc_commit_range(filp, arg);