xfs: refactor agfl length computation function

commit bfdeccb141af8a7eeff5339a17248ffbac80c13e upstream.

Refactor xfs_alloc_min_freelist to accept a NULL @pag argument, in which
case it returns the largest possible minimum length.  This will be used
in an upcoming patch to compute the length of the AGFL at mkfs time.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index f1cdf5fbaa71608cc07952971433647416dce6de..084d39d8856bd4c0cff1380a58450cac194cfb6e 100644 (file)
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -1998,24 +1998,32 @@ xfs_alloc_longest_free_extent(
        return pag->pagf_flcount > 0 || pag->pagf_longest > 0;
 }
 
+/*
+ * Compute the minimum length of the AGFL in the given AG.  If @pag is NULL,
+ * return the largest possible minimum length.
+ */
 unsigned int
 xfs_alloc_min_freelist(
        struct xfs_mount        *mp,
        struct xfs_perag        *pag)
 {
+       /* AG btrees have at least 1 level. */
+       static const uint8_t    fake_levels[XFS_BTNUM_AGF] = {1, 1, 1};
+       const uint8_t           *levels = pag ? pag->pagf_levels : fake_levels;
        unsigned int            min_free;
 
+       ASSERT(mp->m_ag_maxlevels > 0);
+
        /* space needed by-bno freespace btree */
-       min_free = min_t(unsigned int, pag->pagf_levels[XFS_BTNUM_BNOi] + 1,
+       min_free = min_t(unsigned int, levels[XFS_BTNUM_BNOi] + 1,
                                       mp->m_ag_maxlevels);
        /* space needed by-size freespace btree */
-       min_free += min_t(unsigned int, pag->pagf_levels[XFS_BTNUM_CNTi] + 1,
+       min_free += min_t(unsigned int, levels[XFS_BTNUM_CNTi] + 1,
                                       mp->m_ag_maxlevels);
        /* space needed reverse mapping used space btree */
        if (xfs_sb_version_hasrmapbt(&mp->m_sb))
-               min_free += min_t(unsigned int,
-                                 pag->pagf_levels[XFS_BTNUM_RMAPi] + 1,
-                                 mp->m_rmap_maxlevels);
+               min_free += min_t(unsigned int, levels[XFS_BTNUM_RMAPi] + 1,
+                                               mp->m_rmap_maxlevels);
 
        return min_free;
 }