locks: add a new struct file_locking_context pointer to struct inode

The current scheme of using the i_flock list is really difficult to
manage. There is also a legitimate desire for a per-inode spinlock to
manage these lists that isn't the i_lock.

Start conversion to a new scheme to eventually replace the old i_flock
list with a new "file_lock_context" object.

We start by adding a new i_flctx to struct inode. For now, it lives in
parallel with i_flock list, but will eventually replace it. The idea is
to allocate a structure to sit in that pointer and act as a locus for
all things file locking.

We allocate a file_lock_context for an inode when the first lock is
added to it, and it's only freed when the inode is freed. We use the
i_lock to protect the assignment, but afterward it should mostly be
accessed locklessly.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Acked-by: Christoph Hellwig <hch@lst.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/inode.c b/fs/inode.c
index aa149e7262ac..f30872ade6d7 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -194,7 +194,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
 #ifdef CONFIG_FSNOTIFY
         inode->i_fsnotify_mask = 0;
 #endif
-
+        inode->i_flctx = NULL;
         this_cpu_inc(nr_inodes);
 
         return 0;
@@ -237,6 +237,7 @@ void __destroy_inode(struct inode *inode)
         BUG_ON(inode_has_buffers(inode));
         security_inode_free(inode);
         fsnotify_inode_delete(inode);
+        locks_free_lock_context(inode->i_flctx);
         if (!inode->i_nlink) {
                 WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
                 atomic_long_dec(&inode->i_sb->s_remove_count);