[PATCH v2 3/7] nfs: Introduce nfs_release_request_list helper

[Pranjal Shrivastava <praan@google.com>]

Introduce a centralized helper, nfs_release_request_list, to handle
the bulk release of nfs_page requests from a list.

This serves as a preparatory step for two upcoming improvements:

   1. Pin-Aware Cleanup: As we migrate to iov_iter_extract_* API,
      requests will hold pins (GUP) instead of standard references. The
      helper ensures that the correct unpinning logic gets applied
      consistently across all requests in a list.

   2. Folio Support: In subsequent patches where nfs_page structures
      will cover multi-page folios, this helper provides a clean
      infrastructure to unlock these larger units of I/O in bulk during
      completion, similat to the pattern in bio_release_pages.

Additionally, refactor nfs_read_sync_pgio_error() to utilize this new
helper.

Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 fs/nfs/direct.c          |  8 +-------
 fs/nfs/pagelist.c        | 18 ++++++++++++++++++
 include/linux/nfs_page.h |  4 ++--
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 19792a38c924..96995736fac2 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -314,13 +314,7 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
 
 static void nfs_read_sync_pgio_error(struct list_head *head, int error)
 {
-	struct nfs_page *req;
-
-	while (!list_empty(head)) {
-		req = nfs_list_entry(head->next);
-		nfs_list_remove_request(req);
-		nfs_release_request(req);
-	}
+	nfs_release_request_list(head);
 }
 
 static void nfs_direct_pgio_init(struct nfs_pgio_header *hdr)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 7d51e10fe97a..569bac4faff7 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -622,6 +622,24 @@ void nfs_release_request(struct nfs_page *req)
 }
 EXPORT_SYMBOL_GPL(nfs_release_request);
 
+/*
+ * nfs_release_request_list - Release a list of NFS read/write requests
+ * @head: list of requests to release
+ *
+ * Removes each request from the list and drops it's refcount.
+ */
+void nfs_release_request_list(struct list_head *head)
+{
+	struct nfs_page *req;
+
+	while (!list_empty(head)) {
+		req = nfs_list_entry(head->next);
+		nfs_list_remove_request(req);
+		nfs_release_request(req);
+	}
+}
+EXPORT_SYMBOL_GPL(nfs_release_request_list);
+
 /*
  * nfs_generic_pg_test - determine if requests can be coalesced
  * @desc: pointer to descriptor
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index 080fa3e23580..d23208ed3a33 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -136,8 +136,8 @@ extern struct nfs_page *nfs_page_create_from_folio(struct nfs_open_context *ctx,
 						   bool pinned,
 						   unsigned int offset,
 						   unsigned int count);
-extern	void nfs_release_request(struct nfs_page *);
-
+extern void nfs_release_request(struct nfs_page *req);
+extern void nfs_release_request_list(struct list_head *head);
 
 extern	void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
 			     struct inode *inode,
-- 
2.54.0.1136.gdb2ca164c4-goog