3 files changed, 31 insertions, 2 deletions

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 031106020f75..fec8a2bd75b3 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -9,7 +9,10 @@
 #include <linux/dax.h>
 #include <linux/pfn_t.h>
 
-/* Default memory range size, 2MB */
+/*
+ * Default memory range size.  A power of 2 so it agrees with common FUSE_INIT
+ * map_alignment values 4KB and 64KB.
+ */
 #define FUSE_DAX_SHIFT	21
 #define FUSE_DAX_SZ	(1 << FUSE_DAX_SHIFT)
 #define FUSE_DAX_PAGES	(FUSE_DAX_SZ / PAGE_SIZE)
@@ -123,3 +126,13 @@ int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev)
 	fc->dax = fcd;
 	return 0;
 }
+
+bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment)
+{
+	if (fc->dax && (map_alignment > FUSE_DAX_SHIFT)) {
+		pr_warn("FUSE: map_alignment %u incompatible with dax mem range size %u\n",
+			map_alignment, FUSE_DAX_SZ);
+		return false;
+	}
+	return true;
+}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 97af7952373a..2f3f04aa64c7 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1106,5 +1106,6 @@ void fuse_free_conn(struct fuse_conn *fc);
 
 int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev);
 void fuse_dax_conn_free(struct fuse_conn *fc);
+bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment);
 
 #endif /* _FS_FUSE_I_H */
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 1780dfe063ab..67e99cee5a4f 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -908,9 +908,10 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_args *args,
 {
 	struct fuse_init_args *ia = container_of(args, typeof(*ia), args);
 	struct fuse_init_out *arg = &ia->out;
+	bool ok = true;
 
 	if (error || arg->major != FUSE_KERNEL_VERSION)
-		fc->conn_error = 1;
+		ok = false;
 	else {
 		unsigned long ra_pages;
 
@@ -973,6 +974,11 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_args *args,
 					min_t(unsigned int, FUSE_MAX_MAX_PAGES,
 					max_t(unsigned int, arg->max_pages, 1));
 			}
+			if (IS_ENABLED(CONFIG_FUSE_DAX) &&
+			    arg->flags & FUSE_MAP_ALIGNMENT &&
+			    !fuse_dax_check_alignment(fc, arg->map_alignment)) {
+				ok = false;
+			}
 		} else {
 			ra_pages = fc->max_read / PAGE_SIZE;
 			fc->no_lock = 1;
@@ -988,6 +994,11 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_args *args,
 	}
 	kfree(ia);
 
+	if (!ok) {
+		fc->conn_init = 0;
+		fc->conn_error = 1;
+	}
+
 	fuse_set_initialized(fc);
 	wake_up_all(&fc->blocked_waitq);
 }
@@ -1011,6 +1022,10 @@ void fuse_send_init(struct fuse_conn *fc)
 		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
 		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
 		FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA;
+#ifdef CONFIG_FUSE_DAX
+	if (fc->dax)
+		ia->in.flags |= FUSE_MAP_ALIGNMENT;
+#endif
 	ia->args.opcode = FUSE_INIT;
 	ia->args.in_numargs = 1;
 	ia->args.in_args[0].size = sizeof(ia->in);