fs: scale inode alias list

Add a new lock, dcache_inode_lock, to protect the inode's i_dentry list
from concurrent modification. d_alias is also protected by d_lock.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

fs/affs/amigaffs.c

@@ -129,6 +129,7 @@ affs_fix_dcache(struct dentry *dentry, u32 entry_ino)
 	struct list_head *head, *next;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&dcache_inode_lock);
 	head = &inode->i_dentry;
 	next = head->next;
 	while (next != head) {
@@ -139,6 +140,7 @@ affs_fix_dcache(struct dentry *dentry, u32 entry_ino)
 		}
 		next = next->next;
 	}
+	spin_unlock(&dcache_inode_lock);
 	spin_unlock(&dcache_lock);
 }