fuse: make DAX mount option a tri-state

We add 'always', 'never', and 'inode' (default). '-o dax' continues to
operate the same which is equivalent to 'always'.

The following behavior is consistent with that on ext4/xfs:

 - The default behavior (when neither '-o dax' nor
   '-o dax=always|never|inode' option is specified) is equal to 'inode'
   mode, while 'dax=inode' won't be printed among the mount option list.

 - The 'inode' mode is only advisory. It will silently fallback to 'never'
   mode if fuse server doesn't support that.

Also noted that by the time of this commit, 'inode' mode is actually equal
to 'always' mode, before the per inode DAX flag is introduced in the
following patch.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 18 insertions, 2 deletions

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index c1a8b313e6ed..8bf133109170 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -480,6 +480,18 @@ struct fuse_dev {
 	struct list_head entry;
 };
 
+enum fuse_dax_mode {
+	FUSE_DAX_INODE_DEFAULT,	/* default */
+	FUSE_DAX_ALWAYS,	/* "-o dax=always" */
+	FUSE_DAX_NEVER,		/* "-o dax=never" */
+	FUSE_DAX_INODE_USER,	/* "-o dax=inode" */
+};
+
+static inline bool fuse_is_inode_dax_mode(enum fuse_dax_mode mode)
+{
+	return mode == FUSE_DAX_INODE_DEFAULT || mode == FUSE_DAX_INODE_USER;
+}
+
 struct fuse_fs_context {
 	int fd;
 	struct file *file;
@@ -497,7 +509,7 @@ struct fuse_fs_context {
 	bool no_control:1;
 	bool no_force_umount:1;
 	bool legacy_opts_show:1;
-	bool dax:1;
+	enum fuse_dax_mode dax_mode;
 	unsigned int max_read;
 	unsigned int blksize;
 	const char *subtype;
@@ -805,6 +817,9 @@ struct fuse_conn {
 	struct list_head devices;
 
 #ifdef CONFIG_FUSE_DAX
+	/* Dax mode */
+	enum fuse_dax_mode dax_mode;
+
 	/* Dax specific conn data, non-NULL if DAX is enabled */
 	struct fuse_conn_dax *dax;
 #endif
@@ -1272,7 +1287,8 @@ ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to);
 ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from);
 int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma);
 int fuse_dax_break_layouts(struct inode *inode, u64 dmap_start, u64 dmap_end);
-int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev);
+int fuse_dax_conn_alloc(struct fuse_conn *fc, enum fuse_dax_mode mode,
+			struct dax_device *dax_dev);
 void fuse_dax_conn_free(struct fuse_conn *fc);
 bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi);
 void fuse_dax_inode_init(struct inode *inode);