[PATCH v3 4/8] NFS: Keep the readdir pagecache cursor updated

[Benjamin Coddington <bcodding@xxxxxxxxxx>]

Whenever we successfully locate our dir_cookie within the pagecache, or
finish emitting entries to userspace, update the pagecache cursor.  These
updates provide marker points to validate pagecache pages in a future
patch.

Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
---
 fs/nfs/dir.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 009187c0ae0f..2b1a0c1cdce4 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -154,6 +154,10 @@ struct nfs_cache_array {
 	struct nfs_cache_array_entry array[];
 };
 
+static const int cache_entries_per_page =
+	(PAGE_SIZE - sizeof(struct nfs_cache_array)) /
+	sizeof(struct nfs_cache_array_entry);
+
 struct nfs_readdir_descriptor {
 	struct file	*file;
 	struct page	*page;
@@ -282,6 +286,21 @@ static bool nfs_readdir_array_is_full(struct nfs_cache_array *array)
 	return array->page_full;
 }
 
+static void nfs_readdir_set_cursor(struct nfs_readdir_descriptor *desc, int index)
+{
+	desc->pgc.entry_index = index;
+	desc->pgc.index_cookie = desc->dir_cookie;
+}
+
+static void nfs_readdir_cursor_next(struct nfs_dir_page_cursor *pgc, u64 cookie)
+{
+	pgc->index_cookie = cookie;
+	if (++pgc->entry_index == cache_entries_per_page) {
+		pgc->entry_index = 0;
+		pgc->page_index++;
+	}
+}
+
 /*
  * the caller is responsible for freeing qstr.name
  * when called by nfs_readdir_add_to_array, the strings will be freed in
@@ -455,7 +474,7 @@ static int nfs_readdir_search_for_pos(struct nfs_cache_array *array,
 
 	index = (unsigned int)diff;
 	desc->dir_cookie = array->array[index].cookie;
-	desc->pgc.entry_index = index;
+	nfs_readdir_set_cursor(desc, index);
 	return 0;
 out_eof:
 	desc->eof = true;
@@ -524,7 +543,7 @@ static int nfs_readdir_search_for_cookie(struct nfs_cache_array *array,
 			else
 				desc->ctx->pos = new_pos;
 			desc->prev_index = new_pos;
-			desc->pgc.entry_index = i;
+			nfs_readdir_set_cursor(desc, i);
 			return 0;
 		}
 	}
@@ -551,9 +570,9 @@ static int nfs_readdir_search_array(struct nfs_readdir_descriptor *desc)
 		status = nfs_readdir_search_for_cookie(array, desc);
 
 	if (status == -EAGAIN) {
-		desc->pgc.index_cookie = array->last_cookie;
+		desc->pgc.entry_index = array->size - 1;
+		nfs_readdir_cursor_next(&desc->pgc, array->last_cookie);
 		desc->current_index += array->size;
-		desc->pgc.page_index++;
 	}
 	kunmap_atomic(array);
 	return status;
@@ -1084,6 +1103,8 @@ static void nfs_do_filldir(struct nfs_readdir_descriptor *desc,
 		desc->eof = !desc->eob;
 
 	kunmap(desc->page);
+	desc->pgc.entry_index = i-1;
+	nfs_readdir_cursor_next(&desc->pgc, desc->dir_cookie);
 	dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %llu\n",
 			(unsigned long long)desc->dir_cookie);
 }
@@ -1118,8 +1139,7 @@ static int uncached_readdir(struct nfs_readdir_descriptor *desc)
 		goto out;
 
 	desc->pgc.page_index = 0;
-	desc->pgc.entry_index = 0;
-	desc->pgc.index_cookie = desc->dir_cookie;
+	nfs_readdir_set_cursor(desc, 0);
 	desc->duped = 0;
 	desc->page_index_max = 0;
 
-- 
2.31.1