[PATCH 50/51] mkfs.xfs: format reflink enabled filesystems

Darrick J. Wong
2015-10-07T05:10:48Z

Create the refcount btree at mkfs time and set the feature flag.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
man/man8/mkfs.xfs.8 | 28 +++++++++++++++++++++++
mkfs/xfs_mkfs.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/man/man8/mkfs.xfs.8 b/man/man8/mkfs.xfs.8
index 6260e0c..4caf7b1 100644
--- a/man/man8/mkfs.xfs.8
+++ b/man/man8/mkfs.xfs.8
@@ -169,6 +169,34 @@ 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 reference count btrees and therefore will not enable the
+reflink feature. 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 reflink is
+disabled.
.RE
.TP
.BI \-d " data_section_options"
diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 573774c..556b691 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -183,6 +183,8 @@ char *mopts[] = {
"finobt",
#define M_RMAPBT 2
"rmapbt",
+#define M_REFLINK 3
+ "reflink",
NULL
};

@@ -950,6 +952,7 @@ main(
bool finobtflag;
int spinodes;
bool rmapbt;
+ bool reflink;

progname = basename(argv[0]);
setlocale(LC_ALL, "");
@@ -988,6 +991,7 @@ main(
finobtflag = false;
spinodes = 0;
rmapbt = false;
+ reflink = false;
memset(&fsx, 0, sizeof(fsx));

memset(&xi, 0, sizeof(xi));
@@ -1500,6 +1504,14 @@ main(
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);
}
@@ -1862,6 +1874,12 @@ _("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) {
@@ -2479,6 +2497,8 @@ _("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) {
/*
@@ -2542,7 +2562,7 @@ _("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"
@@ -2551,7 +2571,7 @@ _("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,
@@ -2746,7 +2766,10 @@ _("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_refcount_root = cpu_to_be32(xfs_refc_block(mp));
+ agf->agf_refcount_level = cpu_to_be32(1);
+ }
agf->agf_flfirst = 0;
agf->agf_fllast = cpu_to_be32(XFS_AGFL_SIZE(mp) - 1);
agf->agf_flcount = 0;
@@ -2915,6 +2938,23 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
libxfs_writebuf(buf, LIBXFS_EXIT_ON_FAILURE);

/*
+ * refcount btree root block
+ */
+ if (reflink) {
+ buf = libxfs_getbuf(mp->m_ddev_targp,
+ XFS_AGB_TO_DADDR(mp, agno, xfs_refc_block(mp)),
+ bsize);
+ buf->b_ops = &xfs_refcountbt_buf_ops;
+
+ block = XFS_BUF_TO_BLOCK(buf);
+ memset(block, 0, blocksize);
+ xfs_btree_init_block(mp, buf, XFS_REFC_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,
@@ -3002,9 +3042,21 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
rrec->rm_offset = 0;
be16_add_cpu(&block->bb_numrecs, 1);

+ /* account for refcount btree root */
+ if (reflink) {
+ rrec = XFS_RMAP_REC_ADDR(block, 5);
+ rrec->rm_startblock = cpu_to_be32(
+ xfs_refc_block(mp));
+ rrec->rm_blockcount = cpu_to_be32(1);
+ rrec->rm_owner = cpu_to_be64(XFS_RMAP_OWN_REFC);
+ rrec->rm_offset = 0;
+ be16_add_cpu(&block->bb_numrecs, 1);
+ }
+
/* account for the log space */
if (loginternal && agno == logagno) {
- rrec = XFS_RMAP_REC_ADDR(block, 5);
+ rrec = XFS_RMAP_REC_ADDR(block,
+ be16_to_cpu(block->bb_numrecs) + 1);
rrec->rm_startblock = cpu_to_be32(
XFS_FSB_TO_AGBNO(mp, logstart));
rrec->rm_blockcount = cpu_to_be32(logblocks);
@@ -3253,7 +3305,7 @@ 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\