[PATCH v3 1/8] NFS: save the directory's change attribute on pagecache pages

[Benjamin Coddington <bcodding@redhat.com>]

After a pagecache page has been filled with entries, set PagePrivate and
the directory's change attribute on the page.  This will help us perform
per-page invalidations in a later patch.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
---
 fs/nfs/dir.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 9f48c75dbf4c..79bdcedc0cad 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -54,6 +54,9 @@ static int nfs_closedir(struct inode *, struct file *);
 static int nfs_readdir(struct file *, struct dir_context *);
 static int nfs_fsync_dir(struct file *, loff_t, loff_t, int);
 static loff_t nfs_llseek_dir(struct file *, loff_t, int);
+static void nfs_readdir_invalidatepage(struct page *,
+			unsigned int, unsigned int);
+static int nfs_readdir_clear_page(struct page*, gfp_t);
 static void nfs_readdir_clear_array(struct page*);
 
 const struct file_operations nfs_dir_operations = {
@@ -66,6 +69,8 @@ const struct file_operations nfs_dir_operations = {
 };
 
 const struct address_space_operations nfs_dir_aops = {
+	.invalidatepage = nfs_readdir_invalidatepage,
+	.releasepage = nfs_readdir_clear_page,
 	.freepage = nfs_readdir_clear_array,
 };
 
@@ -212,6 +217,27 @@ static void nfs_readdir_page_init_array(struct page *page, u64 last_cookie)
 	array->last_cookie = last_cookie;
 	array->cookies_are_ordered = 1;
 	kunmap_atomic(array);
+	set_page_private(page, 0);
+}
+
+static int
+nfs_readdir_clear_page(struct page *page, gfp_t gfp_mask)
+{
+	detach_page_private(page);
+	return 1;
+}
+
+static void
+nfs_readdir_invalidatepage(struct page *page, unsigned int offset,
+							unsigned int length)
+{
+	nfs_readdir_clear_page(page, GFP_KERNEL);
+}
+
+static void
+nfs_readdir_set_page_verifier(struct page *page, unsigned long verf)
+{
+	attach_page_private(page, (void *)verf);
 }
 
 /*
@@ -794,6 +820,8 @@ static int nfs_readdir_page_filler(struct nfs_readdir_descriptor *desc,
 		if (status != -ENOSPC)
 			continue;
 
+		nfs_readdir_set_page_verifier(page, desc->dir_verifier);
+
 		if (page->mapping != mapping) {
 			if (!--narrays)
 				break;
@@ -822,10 +850,13 @@ static int nfs_readdir_page_filler(struct nfs_readdir_descriptor *desc,
 	case -EBADCOOKIE:
 		if (entry->eof) {
 			nfs_readdir_page_set_eof(page);
+			nfs_readdir_set_page_verifier(page, desc->dir_verifier);
 			status = 0;
 		}
 		break;
 	case -ENOSPC:
+		nfs_readdir_set_page_verifier(page, desc->dir_verifier);
+		fallthrough;
 	case -EAGAIN:
 		status = 0;
 		break;
-- 
2.31.1