From d08d3b3c2caf6c482703bbc5efaa7b9ae95dea20 Mon Sep 17 00:00:00 2001
From: Amir Goldstein
Date: Wed, 16 Aug 2023 12:18:15 +0300
Subject: ovl: split ovl_want_write() into two helpers

ovl_get_write_access() gets write access to upper mnt without taking
freeze protection on upper sb and ovl_start_write() only takes freeze
protection on upper sb.

These helpers will be used to breakup the large ovl_want_write() scope
during copy up into finer grained freeze protection scopes.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/overlayfs.h |  4 ++++
 fs/overlayfs/util.c      | 26 ++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

(limited to 'fs/overlayfs')

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 9817b2dcb132..a22de83e0a9b 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -398,6 +398,10 @@ static inline bool ovl_open_flags_need_copy_up(int flags)
 }
 
 /* util.c */
+int ovl_get_write_access(struct dentry *dentry);
+void ovl_put_write_access(struct dentry *dentry);
+void ovl_start_write(struct dentry *dentry);
+void ovl_end_write(struct dentry *dentry);
 int ovl_want_write(struct dentry *dentry);
 void ovl_drop_write(struct dentry *dentry);
 struct dentry *ovl_workdir(struct dentry *dentry);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 4a9e7efc90aa..80f20ca85344 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -17,12 +17,38 @@
 #include <linux/ratelimit.h>
 #include "overlayfs.h"
 
+/* Get write access to upper mnt - may fail if upper sb was remounted ro */
+int ovl_get_write_access(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	return mnt_get_write_access(ovl_upper_mnt(ofs));
+}
+
+/* Get write access to upper sb - may block if upper sb is frozen */
+void ovl_start_write(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	sb_start_write(ovl_upper_mnt(ofs)->mnt_sb);
+}
+
 int ovl_want_write(struct dentry *dentry)
 {
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	return mnt_want_write(ovl_upper_mnt(ofs));
 }
 
+void ovl_put_write_access(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	mnt_put_write_access(ovl_upper_mnt(ofs));
+}
+
+void ovl_end_write(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	sb_end_write(ovl_upper_mnt(ofs)->mnt_sb);
+}
+
 void ovl_drop_write(struct dentry *dentry)
 {
 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
-- 
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