[PATCH 21/37] NFS: Add comment banners to some NFS functions

[David Howells <dhowells@redhat.com>]

Add comment banners to some NFS functions so that they can be modified by the
NFS fscache patches for further information.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/nfs/file.c |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)


diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index ef57a5a..26a073b 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -354,6 +354,13 @@ static int nfs_write_end(struct file *file, struct address_space *mapping,
 	return copied;
 }
 
+/*
+ * Partially or wholly invalidate a page
+ * - Release the private state associated with a page if undergoing complete
+ *   page invalidation
+ * - Called if either PG_private or PG_private_2 is set on the page
+ * - Caller holds page lock
+ */
 static void nfs_invalidate_page(struct page *page, unsigned long offset)
 {
 	if (offset != 0)
@@ -362,12 +369,26 @@ static void nfs_invalidate_page(struct page *page, unsigned long offset)
 	nfs_wb_page_cancel(page->mapping->host, page);
 }
 
+/*
+ * Attempt to release the private state associated with a page
+ * - Called if either PG_private or PG_private_2 is set on the page
+ * - Caller holds page lock
+ * - Return true (may release page) or false (may not)
+ */
 static int nfs_release_page(struct page *page, gfp_t gfp)
 {
 	/* If PagePrivate() is set, then the page is not freeable */
 	return 0;
 }
 
+/*
+ * Attempt to clear the private state associated with a page when an error
+ * occurs that requires the cached contents of an inode to be written back or
+ * destroyed
+ * - Called if either PG_private or PG_private_2 is set on the page
+ * - Caller holds page lock
+ * - Return 0 if successful, -error otherwise
+ */
 static int nfs_launder_page(struct page *page)
 {
 	return nfs_wb_page(page->mapping->host, page);
@@ -389,6 +410,11 @@ const struct address_space_operations nfs_file_aops = {
 	.launder_page = nfs_launder_page,
 };
 
+/*
+ * Notification that a PTE pointing to an NFS page is about to be made
+ * writable, implying that someone is about to modify the page through a
+ * shared-writable mapping
+ */
 static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct page *page)
 {
 	struct file *filp = vma->vm_file;