[PATCH 4/5] mkfs: Add option to create filesystem with large extent counters

[Chandan Babu R <chandan.babu@oracle.com>]

Enabling nrext64 option on mkfs.xfs command line extends the maximum values of
inode data and attr fork extent counters to 2^48 - 1 and 2^32 - 1
respectively.  This also sets the XFS_SB_FEAT_INCOMPAT_NREXT64 incompat flag
on the superblock preventing older kernels from mounting such a filesystem.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
---
 man/man8/mkfs.xfs.8.in |  7 +++++++
 mkfs/lts_4.19.conf     |  1 +
 mkfs/lts_5.10.conf     |  1 +
 mkfs/lts_5.15.conf     |  1 +
 mkfs/lts_5.4.conf      |  1 +
 mkfs/xfs_mkfs.c        | 23 +++++++++++++++++++++++
 6 files changed, 34 insertions(+)

diff --git a/man/man8/mkfs.xfs.8.in b/man/man8/mkfs.xfs.8.in
index 7b7e4f48..1d8c55f0 100644
--- a/man/man8/mkfs.xfs.8.in
+++ b/man/man8/mkfs.xfs.8.in
@@ -640,6 +640,13 @@ space over time such that no free extents are large enough to
 accommodate a chunk of 64 inodes. Without this feature enabled, inode
 allocations can fail with out of space errors under severe fragmented
 free space conditions.
+.TP
+.BI nrext64[= value]
+Extend maximum values of inode data and attr fork extent counters from 2^31 -
+1 and 2^15 - 1 to 2^48 - 1 and 2^32 - 1 respectively. If the value is
+omitted, 1 is assumed. This feature is disabled by default. This feature is
+only available for filesystems formatted with -m crc=1.
+.TP
 .RE
 .PP
 .PD 0
diff --git a/mkfs/lts_4.19.conf b/mkfs/lts_4.19.conf
index d21fcb7e..751be45e 100644
--- a/mkfs/lts_4.19.conf
+++ b/mkfs/lts_4.19.conf
@@ -2,6 +2,7 @@
 # kernel was released at the end of 2018.
 
 [metadata]
+nrext64=0
 bigtime=0
 crc=1
 finobt=1
diff --git a/mkfs/lts_5.10.conf b/mkfs/lts_5.10.conf
index ac00960e..a1c991ce 100644
--- a/mkfs/lts_5.10.conf
+++ b/mkfs/lts_5.10.conf
@@ -2,6 +2,7 @@
 # kernel was released at the end of 2020.
 
 [metadata]
+nrext64=0
 bigtime=0
 crc=1
 finobt=1
diff --git a/mkfs/lts_5.15.conf b/mkfs/lts_5.15.conf
index 32082958..d751f4c4 100644
--- a/mkfs/lts_5.15.conf
+++ b/mkfs/lts_5.15.conf
@@ -2,6 +2,7 @@
 # kernel was released at the end of 2021.
 
 [metadata]
+nrext64=0
 bigtime=1
 crc=1
 finobt=1
diff --git a/mkfs/lts_5.4.conf b/mkfs/lts_5.4.conf
index dd60b9f1..7e8a0ff0 100644
--- a/mkfs/lts_5.4.conf
+++ b/mkfs/lts_5.4.conf
@@ -2,6 +2,7 @@
 # kernel was released at the end of 2019.
 
 [metadata]
+nrext64=0
 bigtime=0
 crc=1
 finobt=1
diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 8c9ef6fd..52f25e53 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -87,6 +87,7 @@ enum {
 	I_ATTR,
 	I_PROJID32BIT,
 	I_SPINODES,
+	I_NREXT64,
 	I_MAX_OPTS,
 };
 
@@ -441,6 +442,7 @@ static struct opt_params iopts = {
 		[I_ATTR] = "attr",
 		[I_PROJID32BIT] = "projid32bit",
 		[I_SPINODES] = "sparse",
+		[I_NREXT64] = "nrext64",
 	},
 	.subopt_params = {
 		{ .index = I_ALIGN,
@@ -489,6 +491,12 @@ static struct opt_params iopts = {
 		  .maxval = 1,
 		  .defaultval = 1,
 		},
+		{ .index = I_NREXT64,
+		  .conflicts = { { NULL, LAST_CONFLICT } },
+		  .minval = 0,
+		  .maxval = 1,
+		  .defaultval = 1,
+		}
 	},
 };
 
@@ -813,6 +821,7 @@ struct sb_feat_args {
 	bool	bigtime;		/* XFS_SB_FEAT_INCOMPAT_BIGTIME */
 	bool	nodalign;
 	bool	nortalign;
+	bool	nrext64;
 };
 
 struct cli_params {
@@ -1603,6 +1612,9 @@ inode_opts_parser(
 	case I_SPINODES:
 		cli->sb_feat.spinodes = getnum(value, opts, subopt);
 		break;
+	case I_NREXT64:
+		cli->sb_feat.nrext64 = getnum(value, opts, subopt);
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -2180,6 +2192,14 @@ _("timestamps later than 2038 not supported without CRC support\n"));
 			usage();
 		}
 		cli->sb_feat.bigtime = false;
+
+		if (cli->sb_feat.nrext64 &&
+		    cli_opt_set(&iopts, I_NREXT64)) {
+			fprintf(stderr,
+_("64 bit extent count not supported without CRC support\n"));
+			usage();
+		}
+		cli->sb_feat.nrext64 = false;
 	}
 
 	if (!cli->sb_feat.finobt) {
@@ -3172,6 +3192,8 @@ sb_set_features(
 		sbp->sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_SPINODES;
 	}
 
+	if (fp->nrext64)
+		sbp->sb_features_incompat |= XFS_SB_FEAT_INCOMPAT_NREXT64;
 }
 
 /*
@@ -3937,6 +3959,7 @@ main(
 			.nodalign = false,
 			.nortalign = false,
 			.bigtime = true,
+			.nrext64 = false,
 			/*
 			 * When we decide to enable a new feature by default,
 			 * please remember to update the mkfs conf files.
-- 
2.35.1