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[PATCH 12/15] xfs: Introduce a helper to remove an empty

To: xfs@xxxxxxxxxxx
Subject: [PATCH 12/15] xfs: Introduce a helper to remove an empty
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Fri, 16 Nov 2012 14:46:43 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2
If a given AG is empty, we can totally wipe it out of the disk via this
helper by cleaning up the AG metadata blocks.


Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
---
 fs/xfs/xfs_fsops.c |  149 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 149 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index 6623d9a..24de23f 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -706,6 +706,155 @@ error0:
 }
 
 /*
+ * This function is used to remove an empty AG out of the disk
+ * by cleaning up it's metadata info and free the related perag
+ * object.
+ */
+static int
+xfs_remove_empty_ag(
+       xfs_mount_t             *mp,
+       xfs_agnumber_t          agno,
+       xfs_extlen_t            *nfree)
+{
+       xfs_agf_t               *agf;
+       xfs_agi_t               *agi;
+       xfs_buf_t               *bp;
+       xfs_dsb_t               *sbp;
+       xfs_agfl_t              *agfl;
+       xfs_perag_t             *pag;
+       __uint32_t              agfl_bno;
+       __uint32_t              bno_btree_blkno;
+       __uint32_t              cnt_btree_blkno;
+       __uint32_t              ino_btree_blkno;
+       struct xfs_btree_block  *block;
+       int                     error;
+
+       /* Wipe out superblock in sector size */
+       error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
+                         XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
+                         XFS_FSS_TO_BB(mp, 1), 0, &bp);
+       if (error)
+               goto error0;
+       sbp = XFS_BUF_TO_SBP(bp);
+       memset(sbp, 0, mp->m_sb.sb_sectsize);
+       error = xfs_bwrite(bp);
+       xfs_buf_relse(bp);
+       if (error)
+               goto error0;
+
+       bp = xfs_buf_get(mp->m_ddev_targp,
+                        XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
+                        XFS_FSS_TO_BB(mp, 1), 0);
+       if (!bp) {
+               error = ENOMEM;
+               goto error0;
+       }
+       agf = XFS_BUF_TO_AGF(bp);
+       if (nfree) {
+               /*
+                * Don't use the mp->m_sb.sb_agcount since the end
+                * AG might has different size to others.
+                */
+               *nfree = be32_to_cpu(agf->agf_length);
+       }
+       bno_btree_blkno = be32_to_cpu(agf->agf_roots[XFS_BTNUM_BNOi]);
+       cnt_btree_blkno = be32_to_cpu(agf->agf_roots[XFS_BTNUM_CNTi]);
+       memset(agf, 0, mp->m_sb.sb_sectsize);
+       error = xfs_bwrite(bp);
+       xfs_buf_relse(bp);
+       if (error)
+               goto error0;
+
+       bp = xfs_buf_get(mp->m_ddev_targp,
+                        XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
+                        XFS_FSS_TO_BB(mp, 1), 0);
+       if (!bp) {
+               error = ENOMEM;
+               goto error0;
+       }
+       agi = XFS_BUF_TO_AGI(bp);
+       ino_btree_blkno = be32_to_cpu(agi->agi_root);
+       memset(agi, 0, mp->m_sb.sb_sectsize);
+       error = xfs_bwrite(bp);
+       xfs_buf_relse(bp);
+       if (error)
+               goto error0;
+
+       bp = xfs_buf_get(mp->m_ddev_targp,
+                        XFS_AGB_TO_DADDR(mp, agno, XFS_AGFL_BLOCK(mp)),
+                        XFS_FSS_TO_BB(mp, 1), 0);
+       if (!bp) {
+               error = XFS_ERROR(ENOMEM);
+               goto error0;
+       }
+       agfl = XFS_BUF_TO_AGFL(bp);
+       agfl_bno = be32_to_cpu(agfl->agfl_bno[0]);
+       memset(agfl, 0, mp->m_sb.sb_sectsize);
+       error = xfs_bwrite(bp);
+       xfs_buf_relse(bp);
+       if (error)
+               goto error0;
+
+       /* BNO btree root block */
+       bp = xfs_buf_get(mp->m_ddev_targp,
+                        XFS_AGB_TO_DADDR(mp, agno, bno_btree_blkno),
+                        BTOBB(mp->m_sb.sb_blocksize), 0);
+       if (!bp) {
+               error = XFS_ERROR(ENOMEM);
+               goto error0;
+       }
+       block = XFS_BUF_TO_BLOCK(bp);
+       memset(block, 0, mp->m_sb.sb_blocksize);
+       error = xfs_bwrite(bp);
+       xfs_buf_relse(bp);
+       if (error)
+               goto error0;
+
+       /* CNT btree root block */
+       bp = xfs_buf_get(mp->m_ddev_targp,
+                        XFS_AGB_TO_DADDR(mp, agno, cnt_btree_blkno),
+                        BTOBB(mp->m_sb.sb_blocksize), 0);
+       if (!bp) {
+               error = XFS_ERROR(ENOMEM);
+               goto error0;
+       }
+       block = XFS_BUF_TO_BLOCK(bp);
+       memset(block, 0, mp->m_sb.sb_blocksize);
+       error = xfs_bwrite(bp);
+       xfs_buf_relse(bp);
+       if (error)
+               goto error0;
+
+       /* INO btree root block */
+       bp = xfs_buf_get(mp->m_ddev_targp,
+                        XFS_AGB_TO_DADDR(mp, agno, ino_btree_blkno),
+                        BTOBB(mp->m_sb.sb_blocksize), 0);
+       if (!bp) {
+               error = XFS_ERROR(ENOMEM);
+               goto error0;
+       }
+       block = XFS_BUF_TO_BLOCK(bp);
+       memset(block, 0, mp->m_sb.sb_blocksize);
+       error = xfs_bwrite(bp);
+       xfs_buf_relse(bp);
+       if (error)
+               goto error0;
+
+       /* Free perag object from the radix tree */
+       spin_lock(&mp->m_perag_lock);
+       pag = radix_tree_delete(&mp->m_perag_tree, agno);
+       spin_unlock(&mp->m_perag_lock);
+       ASSERT(pag);
+       ASSERT(atomic_read(&pag->pag_ref) == 0);
+       kmem_free(pag);
+
+       *nfree += xfs_ag_metadata_blocks(mp, agno);
+
+error0:
+       return error;
+}
+
+/*
  * exported through ioctl XFS_IOC_FSCOUNTS
  */
 
-- 
1.7.4.1

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