Create the reflink btree at mkfs time.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
man/man8/mkfs.xfs.8 | 26 ++++++++++++++++++++++++++
mkfs/xfs_mkfs.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 70 insertions(+), 4 deletions(-)
diff --git a/man/man8/mkfs.xfs.8 b/man/man8/mkfs.xfs.8
index 6260e0c..c390f51 100644
--- a/man/man8/mkfs.xfs.8
+++ b/man/man8/mkfs.xfs.8
@@ -169,6 +169,32 @@ will create free inode btrees for filesystems created with the (default)
option set. When the option
.B \-m crc=0
is used, the free inode btree feature is not supported and is disabled.
+.TP
+.BI reflink= value
+This option enables the use of a separate reference count btree index in each
+allocation group. The value is either 0 to disable the feature, or 1 to create
+a reference count btree in each allocation group.
+.IP
+The reference count btree enables the sharing of physical extents between
+the data forks of different files, which is commonly known as "reflink".
+Unlike traditional Unix filesystems which assume that every inode and
+logical block pair map to a unique physical block, a reflink-capable
+XFS filesystem removes the uniqueness requirement, allowing up to four
+billion arbitrary inode/logical block pairs to map to a physical block.
+If a program tries to write to a multiply-referenced block in a file, the write
+will be redirected to a new block, and that file's logical-to-physical
+mapping will be changed to the new block ("copy on write"). This feature
+enables the creation of per-file snapshots and deduplication. It is only
+available for the data forks of regular files.
+.IP
+By default,
+.B mkfs.xfs
+will not create reflink btrees. This feature is only available for filesystems
+created with the (default)
+.B \-m crc=1
+option set. When the option
+.B \-m crc=0
+is used, the reference count btree feature is not supported and is disabled.
.RE
.TP
.BI \-d " data_section_options"
diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 5664121..93e3a2f 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -189,6 +189,8 @@ char *mopts[] = {
"finobt",
#define M_RMAPBT 2
"rmapbt",
+#define M_REFLINK 3
+ "reflink",
NULL
};
@@ -1011,6 +1013,7 @@ main(
bool finobtflag;
int spinodes;
bool rmapbt;
+ bool reflink;
progname = basename(argv[0]);
setlocale(LC_ALL, "");
@@ -1048,6 +1051,7 @@ main(
finobtflag = false;
spinodes = 0;
rmapbt = false;
+ reflink = false;
memset(&fsx, 0, sizeof(fsx));
memset(&xi, 0, sizeof(xi));
@@ -1565,6 +1569,14 @@ _("cannot specify both crc and ftype\n"));
illegal(value, "m rmapbt");
rmapbt = c;
break;
+ case M_REFLINK:
+ if (!value || *value == '\0')
+ reqval('m', mopts, M_CRC);
+ c = atoi(value);
+ if (c < 0 || c > 1)
+ illegal(value, "m reflink");
+ reflink = c;
+ break;
default:
unknown('m', value);
}
@@ -1938,6 +1950,12 @@ _("warning: rmapbt not supported without CRC support, disabled.\n"));
rmapbt = 0;
}
+ if (reflink && !crcs_enabled) {
+ fprintf(stderr,
+_("warning: reflink not supported without CRC support, disabled.\n"));
+ reflink = false;
+ }
+
if (nsflag || nlflag) {
if (dirblocksize < blocksize ||
dirblocksize > XFS_MAX_BLOCKSIZE) {
@@ -2555,6 +2573,8 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
sbp->sb_features_ro_compat = XFS_SB_FEAT_RO_COMPAT_FINOBT;
if (rmapbt)
sbp->sb_features_ro_compat |= XFS_SB_FEAT_RO_COMPAT_RMAPBT;
+ if (reflink)
+ sbp->sb_features_ro_compat |= XFS_SB_FEAT_RO_COMPAT_REFLINK;
if (loginternal) {
/*
@@ -2618,7 +2638,7 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
printf(_(
"meta-data=%-22s isize=%-6d agcount=%lld, agsize=%lld blks\n"
" =%-22s sectsz=%-5u attr=%u, projid32bit=%u\n"
- " =%-22s crc=%-8u finobt=%u, sparse=%u, rmapbt=%u\n"
+ " =%-22s crc=%-8u finobt=%u, sparse=%u, rmapbt=%u, reflink=%u\n"
"data =%-22s bsize=%-6u blocks=%llu, imaxpct=%u\n"
" =%-22s sunit=%-6u swidth=%u blks\n"
"naming =version %-14u bsize=%-6u ascii-ci=%d ftype=%d\n"
@@ -2627,7 +2647,7 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
"realtime =%-22s extsz=%-6d blocks=%lld, rtextents=%lld\n"),
dfile, isize, (long long)agcount, (long long)agsize,
"", sectorsize, attrversion, !projid16bit,
- "", crcs_enabled, finobt, spinodes, rmapbt,
+ "", crcs_enabled, finobt, spinodes, rmapbt, reflink,
"", blocksize, (long long)dblocks, imaxpct,
"", dsunit, dswidth,
dirversion, dirblocksize, nci, dirftype,
@@ -2817,7 +2837,10 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
cpu_to_be32(XFS_RMAP_BLOCK(mp));
agf->agf_levels[XFS_BTNUM_RMAPi] = cpu_to_be32(1);
}
-
+ if (reflink) {
+ agf->agf_reflink_root = cpu_to_be32(XFS_RL_BLOCK(mp));
+ agf->agf_reflink_level = cpu_to_be32(1);
+ }
agf->agf_flfirst = 0;
agf->agf_fllast = cpu_to_be32(XFS_AGFL_SIZE(mp) - 1);
agf->agf_flcount = 0;
@@ -2986,6 +3009,23 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
libxfs_writebuf(buf, LIBXFS_EXIT_ON_FAILURE);
/*
+ * reflink btree root block
+ */
+ if (reflink) {
+ buf = libxfs_getbuf(mp->m_ddev_targp,
+ XFS_AGB_TO_DADDR(mp, agno, XFS_RL_BLOCK(mp)),
+ bsize);
+ buf->b_ops = &xfs_reflinkbt_buf_ops;
+
+ block = XFS_BUF_TO_BLOCK(buf);
+ memset(block, 0, blocksize);
+ xfs_btree_init_block(mp, buf, XFS_RLBT_CRC_MAGIC, 0, 0,
+ agno, XFS_BTREE_CRC_BLOCKS);
+
+ libxfs_writebuf(buf, LIBXFS_EXIT_ON_FAILURE);
+ }
+
+ /*
* INO btree root block
*/
buf = libxfs_getbuf(mp->m_ddev_targp,
@@ -3318,7 +3358,7 @@ usage( void )
{
fprintf(stderr, _("Usage: %s\n\
/* blocksize */ [-b log=n|size=num]\n\
-/* metadata */ [-m crc=0|1,finobt=0|1]\n\
+/* metadata */ [-m crc=0|1,finobt=0|1,reflink=0|1]\n\
/* data subvol */ [-d agcount=n,agsize=n,file,name=xxx,size=num,\n\
(sunit=value,swidth=value|su=num,sw=num|noalign),\n\
sectlog=n|sectsize=num\n\
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