nfs: use locks_inode_context helper

nfs currently doesn't access i_flctx safely. This requires a
smp_load_acquire, as the pointer is set via cmpxchg (a release
operation).

Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

fs/nfs/delegation.c

@@ -146,7 +146,7 @@ static int nfs_delegation_claim_locks(struct nfs4_state *state, const nfs4_state
 {
 	struct inode *inode = state->inode;
 	struct file_lock *fl;
-	struct file_lock_context *flctx = inode->i_flctx;
+	struct file_lock_context *flctx = locks_inode_context(inode);
 	struct list_head *list;
 	int status = 0;
 

fs/nfs/nfs4state.c

@@ -1501,7 +1501,7 @@ static int nfs4_reclaim_locks(struct nfs4_state *state, const struct nfs4_state_
 	struct file_lock *fl;
 	struct nfs4_lock_state *lsp;
 	int status = 0;
-	struct file_lock_context *flctx = inode->i_flctx;
+	struct file_lock_context *flctx = locks_inode_context(inode);
 	struct list_head *list;
 
 	if (flctx == NULL)

fs/nfs/pagelist.c

@@ -1055,7 +1055,7 @@ static unsigned int nfs_coalesce_size(struct nfs_page *prev,
 	if (prev) {
 		if (!nfs_match_open_context(nfs_req_openctx(req), nfs_req_openctx(prev)))
 			return 0;
-		flctx = d_inode(nfs_req_openctx(req)->dentry)->i_flctx;
+		flctx = locks_inode_context(d_inode(nfs_req_openctx(req)->dentry));
 		if (flctx != NULL &&
 		    !(list_empty_careful(&flctx->flc_posix) &&
 		      list_empty_careful(&flctx->flc_flock)) &&

fs/nfs/write.c

@@ -1185,7 +1185,7 @@ int nfs_flush_incompatible(struct file *file, struct page *page)
 {
 	struct nfs_open_context *ctx = nfs_file_open_context(file);
 	struct nfs_lock_context *l_ctx;
-	struct file_lock_context *flctx = file_inode(file)->i_flctx;
+	struct file_lock_context *flctx = locks_inode_context(file_inode(file));
 	struct nfs_page	*req;
 	int do_flush, status;
 	/*
@@ -1321,7 +1321,7 @@ static int nfs_can_extend_write(struct file *file, struct page *page,
 				struct inode *inode, unsigned int pagelen)
 {
 	int ret;
-	struct file_lock_context *flctx = inode->i_flctx;
+	struct file_lock_context *flctx = locks_inode_context(inode);
 	struct file_lock *fl;
 
 	if (file->f_flags & O_DSYNC)