xfs: clean up xfs_mount allocation and dynamic initializers

Most of the generic data structures embedded in xfs_mount are
dynamically initialized immediately after mp is allocated. A few
fields are left out and initialized during the xfs_mountfs()
sequence, after mp has been attached to the superblock.

To clean this up and help prevent premature access of associated
fields, refactor xfs_mount allocation and all dependent init calls
into a new helper. This self-documents that all low level data
structures (i.e., locks, trees, etc.) should be initialized before
xfs_mount is attached to the superblock.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

3 files changed, 29 insertions, 13 deletions

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index a55f7a45fa78..53433cc024fd 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -731,7 +731,6 @@ xfs_sb_mount_common(
         struct xfs_sb   *sbp)
 {
         mp->m_agfrotor = mp->m_agirotor = 0;
-        spin_lock_init(&mp->m_agirotor_lock);
         mp->m_maxagi = mp->m_sb.sb_agcount;
         mp->m_blkbit_log = sbp->sb_blocklog + XFS_NBBYLOG;
         mp->m_blkbb_log = sbp->sb_blocklog - BBSHIFT;
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 6f5a5e6764d8..a901b86772f8 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -817,8 +817,6 @@ xfs_mountfs(
         /*
          * Allocate and initialize the per-ag data.
          */
-        spin_lock_init(&mp->m_perag_lock);
-        INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);
         error = xfs_initialize_perag(mp, sbp->sb_agcount, &mp->m_maxagi);
         if (error) {
                 xfs_warn(mp, "Failed per-ag init: %d", error);
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 951271f57d00..612c1d5348b3 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1579,29 +1579,48 @@ xfs_destroy_percpu_counters(
         percpu_counter_destroy(&mp->m_fdblocks);
 }
 
-STATIC int
-xfs_fs_fill_super(
-        struct super_block      *sb,
-        void                    *data,
-        int                     silent)
+static struct xfs_mount *
+xfs_mount_alloc(
+        struct super_block      *sb)
 {
-        struct inode            *root;
-        struct xfs_mount        *mp = NULL;
-        int                     flags = 0, error = -ENOMEM;
+        struct xfs_mount        *mp;
 
         mp = kzalloc(sizeof(struct xfs_mount), GFP_KERNEL);
         if (!mp)
-                goto out;
+                return NULL;
 
+        mp->m_super = sb;
         spin_lock_init(&mp->m_sb_lock);
+        spin_lock_init(&mp->m_agirotor_lock);
+        INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);
+        spin_lock_init(&mp->m_perag_lock);
         mutex_init(&mp->m_growlock);
         atomic_set(&mp->m_active_trans, 0);
         INIT_DELAYED_WORK(&mp->m_reclaim_work, xfs_reclaim_worker);
         INIT_DELAYED_WORK(&mp->m_eofblocks_work, xfs_eofblocks_worker);
         INIT_DELAYED_WORK(&mp->m_cowblocks_work, xfs_cowblocks_worker);
         mp->m_kobj.kobject.kset = xfs_kset;
+        return mp;
+}
 
-        mp->m_super = sb;
+
+STATIC int
+xfs_fs_fill_super(
+        struct super_block      *sb,
+        void                    *data,
+        int                     silent)
+{
+        struct inode            *root;
+        struct xfs_mount        *mp = NULL;
+        int                     flags = 0, error = -ENOMEM;
+
+        /*
+         * allocate mp and do all low-level struct initializations before we
+         * attach it to the super
+         */
+        mp = xfs_mount_alloc(sb);
+        if (!mp)
+                goto out;
         sb->s_fs_info = mp;
 
         error = xfs_parseargs(mp, (char *)data);