[PATCH 1/2] xfs_db: add inobtcnt upgrade path

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

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

Enable users to upgrade their filesystems to support inode btree block
counters.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 db/sb.c              |   22 ++++++++++++++++++++++
 man/man8/xfs_admin.8 |    7 +++++++
 man/man8/xfs_db.8    |    3 +++
 3 files changed, 32 insertions(+)


diff --git a/db/sb.c b/db/sb.c
index fcc2a0ed..767bc858 100644
--- a/db/sb.c
+++ b/db/sb.c
@@ -597,6 +597,7 @@ version_help(void)
 " 'version attr2'    - enable v2 inline extended attributes\n"
 " 'version log2'     - enable v2 log format\n"
 " 'version needsrepair' - flag filesystem as requiring repair\n"
+" 'version inobtcount' - enable inode btree counters\n"
 "\n"
 "The version function prints currently enabled features for a filesystem\n"
 "according to the version field of its primary superblock.\n"
@@ -852,6 +853,27 @@ version_f(
 			}
 
 			v5features.incompat |= XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
+		} else if (!strcasecmp(argv[1], "inobtcount")) {
+			if (xfs_sb_version_hasinobtcounts(&mp->m_sb)) {
+				dbprintf(
+		_("inode btree counter feature is already enabled\n"));
+				exitcode = 2;
+				return 1;
+			}
+			if (!xfs_sb_version_hasfinobt(&mp->m_sb)) {
+				dbprintf(
+		_("inode btree counter feature cannot be enabled on filesystems lacking free inode btrees\n"));
+				exitcode = 2;
+				return 1;
+			}
+			if (!xfs_sb_version_hascrc(&mp->m_sb)) {
+				dbprintf(
+		_("inode btree counter feature cannot be enabled on pre-V5 filesystems\n"));
+				exitcode = 2;
+				return 1;
+			}
+
+			v5features.ro_compat |= XFS_SB_FEAT_RO_COMPAT_INOBTCNT;
 		} else if (!strcasecmp(argv[1], "extflg")) {
 			switch (XFS_SB_VERSION_NUM(&mp->m_sb)) {
 			case XFS_SB_VERSION_1:
diff --git a/man/man8/xfs_admin.8 b/man/man8/xfs_admin.8
index b423981d..a776b375 100644
--- a/man/man8/xfs_admin.8
+++ b/man/man8/xfs_admin.8
@@ -116,6 +116,13 @@ If this is a V5 filesystem, flag the filesystem as needing repairs.
 Until
 .BR xfs_repair (8)
 is run, the filesystem will not be mountable.
+.TP
+.B inobtcount
+Upgrade a V5 filesystem to support the inode btree counters feature.
+This reduces mount time by caching the size of the inode btrees in the
+allocation group metadata.
+Once enabled, the filesystem will not be writable by older kernels.
+The filesystem cannot be downgraded after this feature is enabled.
 .RE
 .TP
 .BI \-U " uuid"
diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
index 7331cf19..1b826e5d 100644
--- a/man/man8/xfs_db.8
+++ b/man/man8/xfs_db.8
@@ -976,6 +976,9 @@ The filesystem can be flagged as requiring a run through
 if the
 .B needsrepair
 option is specified and the filesystem is formatted with the V5 format.
+Support for the inode btree counters feature can be enabled by using the
+.B inobtcount
+option if the filesystem is formatted with the V5 format.
 .IP
 If no argument is given, the current version and feature bits are printed.
 With one argument, this command will write the updated version number