3 files changed, 14 insertions, 3 deletions

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e6195bc8f836..24dbca777775 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -694,6 +694,9 @@ struct fuse_conn {
         /** Use enhanced/automatic page cache invalidation. */
         unsigned auto_inval_data:1;
 
+        /** Filesystem is fully reponsible for page cache invalidation. */
+        unsigned explicit_inval_data:1;
+
         /** Does the filesystem support readdirplus? */
         unsigned do_readdirplus:1;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 36981ea7eac0..c67b39e88fd5 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -237,7 +237,8 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
 
                 if (oldsize != attr->size) {
                         truncate_pagecache(inode, attr->size);
-                        inval = true;
+                        if (!fc->explicit_inval_data)
+                                inval = true;
                 } else if (fc->auto_inval_data) {
                         struct timespec64 new_mtime = {
                                 .tv_sec = attr->mtime,
@@ -912,6 +913,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
                                 fc->dont_mask = 1;
                         if (arg->flags & FUSE_AUTO_INVAL_DATA)
                                 fc->auto_inval_data = 1;
+                        else if (arg->flags & FUSE_EXPLICIT_INVAL_DATA)
+                                fc->explicit_inval_data = 1;
                         if (arg->flags & FUSE_DO_READDIRPLUS) {
                                 fc->do_readdirplus = 1;
                                 if (arg->flags & FUSE_READDIRPLUS_AUTO)
@@ -973,7 +976,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
                 FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
                 FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
                 FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
-                FUSE_NO_OPENDIR_SUPPORT;
+                FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA;
         req->in.h.opcode = FUSE_INIT;
         req->in.numargs = 1;
         req->in.args[0].size = sizeof(*arg);
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 2ac598614a8f..36899cfcb654 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -125,6 +125,9 @@
  *
  *  7.29
  *  - add FUSE_NO_OPENDIR_SUPPORT flag
+ *
+ *  7.30
+ *  - add FUSE_EXPLICIT_INVAL_DATA
  */
 
 #ifndef _LINUX_FUSE_H
@@ -160,7 +163,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 29
+#define FUSE_KERNEL_MINOR_VERSION 30
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -263,6 +266,7 @@ struct fuse_file_lock {
  * FUSE_MAX_PAGES: init_out.max_pages contains the max number of req pages
  * FUSE_CACHE_SYMLINKS: cache READLINK responses
  * FUSE_NO_OPENDIR_SUPPORT: kernel supports zero-message opendir
+ * FUSE_EXPLICIT_INVAL_DATA: only invalidate cached pages on explicit request
  */
 #define FUSE_ASYNC_READ         (1 << 0)
 #define FUSE_POSIX_LOCKS        (1 << 1)
@@ -289,6 +293,7 @@ struct fuse_file_lock {
 #define FUSE_MAX_PAGES          (1 << 22)
 #define FUSE_CACHE_SYMLINKS     (1 << 23)
 #define FUSE_NO_OPENDIR_SUPPORT (1 << 24)
+#define FUSE_EXPLICIT_INVAL_DATA (1 << 25)
 
 /**
  * CUSE INIT request/reply flags