Inode: Allow external list initialisation

To allow XFS to combine the XFS and linux inodes into a single
structure, we need to drive inode lookup from the XFS inode cache,
not the generic inode cache. This means that we need initialise a
struct inode from a context outside alloc_inode() as it is no longer
used by XFS.

After inode allocation and initialisation, we need to add the inode
to the superblock list, the in-use list, hash it and do some
accounting. This all needs to be done with the inode_lock held and
there are already several places in fs/inode.c that do this list
manipulation.  Factor out the common code, add a locking wrapper and
export the function so ti can be called from XFS.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

2 files changed, 47 insertions, 21 deletions

diff --git a/fs/inode.c b/fs/inode.c
index e7ee99907d60..fbcf6c5e7605 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -550,6 +550,49 @@ repeat:
         return node ? inode : NULL;
 }
 
+static unsigned long hash(struct super_block *sb, unsigned long hashval)
+{
+        unsigned long tmp;
+
+        tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
+                        L1_CACHE_BYTES;
+        tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS);
+        return tmp & I_HASHMASK;
+}
+
+static inline void
+__inode_add_to_lists(struct super_block *sb, struct hlist_head *head,
+                        struct inode *inode)
+{
+        inodes_stat.nr_inodes++;
+        list_add(&inode->i_list, &inode_in_use);
+        list_add(&inode->i_sb_list, &sb->s_inodes);
+        if (head)
+                hlist_add_head(&inode->i_hash, head);
+}
+
+/**
+ * inode_add_to_lists - add a new inode to relevant lists
+ * @sb          - superblock inode belongs to.
+ * @inode       - inode to mark in use
+ *
+ * When an inode is allocated it needs to be accounted for, added to the in use
+ * list, the owning superblock and the inode hash. This needs to be done under
+ * the inode_lock, so export a function to do this rather than the inode lock
+ * itself. We calculate the hash list to add to here so it is all internal
+ * which requires the caller to have already set up the inode number in the
+ * inode to add.
+ */
+void inode_add_to_lists(struct super_block *sb, struct inode *inode)
+{
+        struct hlist_head *head = inode_hashtable + hash(sb, inode->i_ino);
+
+        spin_lock(&inode_lock);
+        __inode_add_to_lists(sb, head, inode);
+        spin_unlock(&inode_lock);
+}
+EXPORT_SYMBOL_GPL(inode_add_to_lists);
+
 /**
  *      new_inode       - obtain an inode
  *      @sb: superblock
@@ -577,9 +620,7 @@ struct inode *new_inode(struct super_block *sb)
         inode = alloc_inode(sb);
         if (inode) {
                 spin_lock(&inode_lock);
-                inodes_stat.nr_inodes++;
-                list_add(&inode->i_list, &inode_in_use);
-                list_add(&inode->i_sb_list, &sb->s_inodes);
+                __inode_add_to_lists(sb, NULL, inode);
                 inode->i_ino = ++last_ino;
                 inode->i_state = 0;
                 spin_unlock(&inode_lock);
@@ -638,10 +679,7 @@ static struct inode * get_new_inode(struct super_block *sb, struct hlist_head *h
                         if (set(inode, data))
                                 goto set_failed;
 
-                        inodes_stat.nr_inodes++;
-                        list_add(&inode->i_list, &inode_in_use);
-                        list_add(&inode->i_sb_list, &sb->s_inodes);
-                        hlist_add_head(&inode->i_hash, head);
+                        __inode_add_to_lists(sb, head, inode);
                         inode->i_state = I_LOCK|I_NEW;
                         spin_unlock(&inode_lock);
 
@@ -687,10 +725,7 @@ static struct inode * get_new_inode_fast(struct super_block *sb, struct hlist_he
                 old = find_inode_fast(sb, head, ino);
                 if (!old) {
                         inode->i_ino = ino;
-                        inodes_stat.nr_inodes++;
-                        list_add(&inode->i_list, &inode_in_use);
-                        list_add(&inode->i_sb_list, &sb->s_inodes);
-                        hlist_add_head(&inode->i_hash, head);
+                        __inode_add_to_lists(sb, head, inode);
                         inode->i_state = I_LOCK|I_NEW;
                         spin_unlock(&inode_lock);
 
@@ -714,16 +749,6 @@ static struct inode * get_new_inode_fast(struct super_block *sb, struct hlist_he
         return inode;
 }
 
-static unsigned long hash(struct super_block *sb, unsigned long hashval)
-{
-        unsigned long tmp;
-
-        tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
-                        L1_CACHE_BYTES;
-        tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> I_HASHBITS);
-        return tmp & I_HASHMASK;
-}
-
 /**
  *      iunique - get a unique inode number
  *      @sb: superblock
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 04abead4b021..1deedf235d55 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1883,6 +1883,7 @@ extern loff_t vfs_llseek(struct file *file, loff_t offset, int origin);
 
 extern struct inode * inode_init_always(struct super_block *, struct inode *);
 extern void inode_init_once(struct inode *);
+extern void inode_add_to_lists(struct super_block *, struct inode *);
 extern void iput(struct inode *);
 extern struct inode * igrab(struct inode *);
 extern ino_t iunique(struct super_block *, ino_t);