[PATCH 3/3] xfs: add an option to enable reflinks at mount time

[Christoph Hellwig <hch@lst.de>]

If the reflink mount option is specified we'll add the reflink btree root
block to each AG late in the mount process and can then use the reflink
tree.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/libxfs/xfs_refcount_btree.c | 83 ++++++++++++++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_refcount_btree.h |  2 +
 fs/xfs/libxfs/xfs_trans_resv.c     | 23 +++++++++++
 fs/xfs/libxfs/xfs_trans_resv.h     |  1 +
 fs/xfs/xfs_mount.c                 | 24 +++++++++--
 fs/xfs/xfs_mount.h                 |  5 ++-
 fs/xfs/xfs_super.c                 |  7 +++-
 7 files changed, 139 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_refcount_btree.c b/fs/xfs/libxfs/xfs_refcount_btree.c
index 7ae3ad7..aaea8da 100644
--- a/fs/xfs/libxfs/xfs_refcount_btree.c
+++ b/fs/xfs/libxfs/xfs_refcount_btree.c
@@ -484,3 +484,86 @@ xfs_refcountbt_calc_reserves(
 
 	return error;
 }
+
+static int
+xfs_reflink_ag_add(
+	struct xfs_trans	*tp,
+	xfs_agnumber_t		agno)
+{
+	struct xfs_mount	*mp = tp->t_mountp;
+	struct xfs_perag	*pag;
+	struct xfs_buf		*bp, *agbp;
+	struct xfs_agf		*agf;
+	__be32			bno;
+	int			stat, error;
+
+	error = __xfs_refcountbt_alloc_block(tp, agno, XFS_AG_RESV_NONE,
+			&bno, &stat);
+	if (error)
+		return error;
+
+	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
+			XFS_AGB_TO_DADDR(mp, agno, be32_to_cpu(bno)),
+			mp->m_bsize, 0);
+	if (!bp)
+		return -ENOMEM;
+
+	bp->b_ops = &xfs_refcountbt_buf_ops;
+	xfs_btree_init_block(mp, bp, XFS_REFC_CRC_MAGIC, 0, 0, agno,
+		XFS_BTREE_CRC_BLOCKS);
+	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_BTREE_BUF);
+	xfs_trans_log_buf(tp, bp, 0, XFS_BTREE_SBLOCK_CRC_LEN - 1);
+
+	error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp);
+	if (error)
+		return error;
+
+	agf = XFS_BUF_TO_AGF(agbp);
+	agf->agf_refcount_root = bno;
+	agf->agf_refcount_level = cpu_to_be32(1);
+
+	pag = xfs_perag_get(mp, agno);
+	pag->pagf_refcount_level = 1;
+	xfs_perag_put(pag);
+
+	xfs_alloc_log_agf(tp, agbp,
+			XFS_AGF_REFCOUNT_ROOT | XFS_AGF_REFCOUNT_LEVEL);
+	return 0;
+}
+
+int
+xfs_reflink_add(
+	struct xfs_mount	*mp)
+{
+	struct xfs_trans	*tp = NULL;
+	int			error, i;
+
+	tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);
+	tp->t_flags |= XFS_TRANS_RESERVE;
+	error = xfs_trans_reserve(tp, &M_RES(mp)->tr_add_reflink,
+			mp->m_sb.sb_agcount, 0);
+	if (error)
+		goto out_trans_cancel;
+
+	for (i = 0; i < mp->m_sb.sb_agcount; i++) {
+		xfs_log_sb(tp);
+
+		error = xfs_reflink_ag_add(tp, i);
+		if (error)
+			goto out_trans_cancel;
+
+		error = xfs_trans_roll(&tp, NULL);
+		if (error)
+			goto out_trans_cancel;
+	}
+
+	mp->m_sb.sb_features_ro_compat |= XFS_SB_FEAT_RO_COMPAT_REFLINK;
+	xfs_log_sb(tp);
+
+	return xfs_trans_commit(tp);
+
+out_trans_cancel:
+	if (tp)
+		xfs_trans_cancel(tp);
+	return error;
+}
diff --git a/fs/xfs/libxfs/xfs_refcount_btree.h b/fs/xfs/libxfs/xfs_refcount_btree.h
index 6f4bf70..481e0d0 100644
--- a/fs/xfs/libxfs/xfs_refcount_btree.h
+++ b/fs/xfs/libxfs/xfs_refcount_btree.h
@@ -70,4 +70,6 @@ extern xfs_extlen_t xfs_refcountbt_max_size(struct xfs_mount *mp);
 extern int xfs_refcountbt_calc_reserves(struct xfs_mount *mp,
 		xfs_agnumber_t agno, xfs_extlen_t *ask, xfs_extlen_t *used);
 
+extern int xfs_reflink_add(struct xfs_mount *mp);
+
 #endif	/* __XFS_REFCOUNT_BTREE_H__ */
diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
index d53fe89..346c0c1 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.c
+++ b/fs/xfs/libxfs/xfs_trans_resv.c
@@ -802,6 +802,25 @@ xfs_calc_sb_reservation(
 	return xfs_calc_buf_res(1, mp->m_sb.sb_sectsize);
 }
 
+/*
+ * For adding the reflinking we need to allocate the new root block
+ * and modify the AGF and SB, giving:
+ *    the AGF: sectorsize
+ *    the superblock for the reflink flag: sector size
+ *    the reflink root block itself: sector size
+ *    the allocation btrees: 2 trees * (max depth - 1) * block size
+ */
+STATIC uint
+xfs_calc_add_reflink_resv_alloc(
+	struct xfs_mount	*mp)
+{
+	return xfs_calc_buf_res(1, mp->m_sb.sb_sectsize) +
+		mp->m_sb.sb_sectsize +
+		mp->m_sb.sb_sectsize +
+		xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1),
+				 XFS_FSB_TO_B(mp, 1));
+}
+
 void
 xfs_trans_resv_calc(
 	struct xfs_mount	*mp,
@@ -885,6 +904,10 @@ xfs_trans_resv_calc(
 		resp->tr_qm_dqalloc.tr_logcount = XFS_WRITE_LOG_COUNT;
 	resp->tr_qm_dqalloc.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 
+	resp->tr_add_reflink.tr_logres = xfs_calc_add_reflink_resv_alloc(mp);
+	resp->tr_add_reflink.tr_logcount = XFS_DEFAULT_LOG_COUNT;
+	resp->tr_add_reflink.tr_logflags = XFS_TRANS_PERM_LOG_RES;
+
 	/*
 	 * The following transactions are logged in logical format with
 	 * a default log count.
diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
index cf734cf..1c007da 100644
--- a/fs/xfs/libxfs/xfs_trans_resv.h
+++ b/fs/xfs/libxfs/xfs_trans_resv.h
@@ -60,6 +60,7 @@ struct xfs_trans_resv {
 	struct xfs_trans_res	tr_qm_dqalloc;	/* allocate quota on disk */
 	struct xfs_trans_res	tr_qm_quotaoff;	/* turn quota off */
 	struct xfs_trans_res	tr_qm_equotaoff;/* end of turn quota off */
+	struct xfs_trans_res	tr_add_reflink; /* add reflink */
 	struct xfs_trans_res	tr_sb;		/* modify superblock */
 	struct xfs_trans_res	tr_fsyncts;	/* update timestamps on fsync */
 };
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 792f547..6e4cebf 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -962,11 +962,27 @@ xfs_mountfs(
 
 		xfs_fs_reserve_ag_blocks(mp);
 
-		/* Recover any CoW blocks that never got remapped. */
-		error = xfs_reflink_recover_cow(mp);
-		if (error && !XFS_FORCED_SHUTDOWN(mp))
-			xfs_err(mp,
+		if (!xfs_sb_version_hasreflink(&mp->m_sb) &&
+		    (mp->m_flags & XFS_MOUNT_REFLINK)) {
+			if (XFS_SB_VERSION_NUM(&mp->m_sb) < XFS_SB_VERSION_5) {
+				xfs_warn(mp,
+	"Can't enable reflinks on version %d superblock.",
+					XFS_SB_VERSION_NUM(&mp->m_sb));
+				return -EINVAL;
+			}
+
+			error = xfs_reflink_add(mp);
+			if (error) {
+				xfs_err(mp,
+	"Failed to enable reflinks: %d\n", error);
+			}
+		} else {
+			/* Recover any CoW blocks that never got remapped. */
+			error = xfs_reflink_recover_cow(mp);
+			if (error && !XFS_FORCED_SHUTDOWN(mp))
+				xfs_err(mp,
 	"Error %d recovering leftover CoW allocations.", error);
+		}
 	}
 
 	return 0;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index c2e1294..e3002cb 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -178,6 +178,8 @@ typedef struct xfs_mount {
 #define XFS_MOUNT_WSYNC		(1ULL << 0)	/* for nfs - all metadata ops
 						   must be synchronous except
 						   for space allocations */
+#define XFS_MOUNT_REFLINK	(1ULL << 1)	/* allow use of reflinks (will
+						   be permanent once used) */
 #define XFS_MOUNT_WAS_CLEAN	(1ULL << 3)
 #define XFS_MOUNT_FS_SHUTDOWN	(1ULL << 4)	/* atomic stop of all filesystem
 						   operations, typically for
@@ -229,7 +231,8 @@ typedef struct xfs_mount {
 
 static inline bool xfs_mp_hasreflink(struct xfs_mount *mp)
 {
-	return xfs_sb_version_hasreflink(&mp->m_sb);
+	return xfs_sb_version_hasreflink(&mp->m_sb) ||
+		(mp->m_flags & XFS_MOUNT_REFLINK);
 }
 
 /*
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 84348af..dfa5077 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -82,7 +82,7 @@ enum {
 	Opt_quota, Opt_noquota, Opt_usrquota, Opt_grpquota, Opt_prjquota,
 	Opt_uquota, Opt_gquota, Opt_pquota,
 	Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
-	Opt_discard, Opt_nodiscard, Opt_dax, Opt_err,
+	Opt_discard, Opt_nodiscard, Opt_reflink, Opt_dax, Opt_err,
 };
 
 static const match_table_t tokens = {
@@ -132,6 +132,7 @@ static const match_table_t tokens = {
 	{Opt_qnoenforce, "qnoenforce"},	/* same as uqnoenforce */
 	{Opt_discard,	"discard"},	/* Discard unused blocks */
 	{Opt_nodiscard,	"nodiscard"},	/* Do not discard unused blocks */
+	{Opt_reflink,	"reflink"},	/* Do not discard unused blocks */
 
 	{Opt_dax,	"dax"},		/* Enable direct access to bdev pages */
 	{Opt_err,	NULL},
@@ -219,6 +220,7 @@ xfs_parseargs(
 	 */
 	mp->m_flags |= XFS_MOUNT_BARRIER;
 	mp->m_flags |= XFS_MOUNT_COMPAT_IOSIZE;
+	mp->m_flags |= XFS_MOUNT_REFLINK;
 
 	/*
 	 * These can be overridden by the mount option parsing.
@@ -368,6 +370,9 @@ xfs_parseargs(
 		case Opt_nodiscard:
 			mp->m_flags &= ~XFS_MOUNT_DISCARD;
 			break;
+		case Opt_reflink:
+			mp->m_flags |= XFS_MOUNT_REFLINK;
+			break;
 #ifdef CONFIG_FS_DAX
 		case Opt_dax:
 			mp->m_flags |= XFS_MOUNT_DAX;
-- 
2.1.4

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