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

To: darrick.wong@xxxxxxxxxx
Subject: [PATCH 3/3] xfs: add an option to enable reflinks at mount time
From: Christoph Hellwig <hch@xxxxxx>
Date: Thu, 2 Jun 2016 16:19:10 +0200
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1464877150-20457-1-git-send-email-hch@xxxxxx>
References: <1464877150-20457-1-git-send-email-hch@xxxxxx>
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@xxxxxx>
---
 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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