We add 'always', 'never', and 'inode' (default). '-o dax' continues to
operate the same which is equivalent to 'always'. To be consistemt with
ext4/xfs's tri-state mount option, when neither '-o dax' nor '-o dax='
option is specified, the default behaviour is equal to 'inode'.

By the time this patch is applied, 'inode' mode is actually equal to
'always' mode, before the per-file DAX flag is introduced in the
following patch.

Signed-off-by: Jeffle Xu <[email protected]>
---
 fs/fuse/dax.c       | 19 ++++++++++++++++---
 fs/fuse/fuse_i.h    | 14 ++++++++++++--
 fs/fuse/inode.c     | 10 +++++++---
 fs/fuse/virtio_fs.c | 16 ++++++++++++++--
 4 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 1eb6538bf1b2..4c6c64efc950 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -1284,11 +1284,14 @@ static int fuse_dax_mem_range_init(struct fuse_conn_dax 
*fcd)
        return ret;
 }
 
-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 dax_mode,
+                       struct dax_device *dax_dev)
 {
        struct fuse_conn_dax *fcd;
        int err;
 
+       fc->dax_mode = dax_mode;
+
        if (!dax_dev)
                return 0;
 
@@ -1335,11 +1338,21 @@ static const struct address_space_operations 
fuse_dax_file_aops  = {
 static bool fuse_should_enable_dax(struct inode *inode)
 {
        struct fuse_conn *fc = get_fuse_conn(inode);
+       unsigned int dax_mode = fc->dax_mode;
+
+       if (dax_mode == FUSE_DAX_NEVER)
+               return false;
 
-       if (fc->dax)
+       /*
+        * If 'dax=always/inode', fc->dax couldn't be NULL even when fuse
+        * daemon doesn't support DAX, since the mount routine will fail
+        * early in this case.
+        */
+       if (dax_mode == FUSE_DAX_ALWAYS)
                return true;
 
-       return false;
+       /* dax_mode == FUSE_DAX_INODE */
+       return true;
 }
 
 void fuse_dax_inode_init(struct inode *inode)
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 319596df5dc6..5abf9749923f 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -480,6 +480,12 @@ struct fuse_dev {
        struct list_head entry;
 };
 
+enum fuse_dax_mode {
+       FUSE_DAX_INODE,
+       FUSE_DAX_ALWAYS,
+       FUSE_DAX_NEVER,
+};
+
 struct fuse_fs_context {
        int fd;
        struct file *file;
@@ -497,7 +503,7 @@ 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;
@@ -802,6 +808,9 @@ struct fuse_conn {
        struct list_head devices;
 
 #ifdef CONFIG_FUSE_DAX
+       /* dax mode: FUSE_DAX_* (always, never or per-file) */
+       enum fuse_dax_mode dax_mode;
+
        /* Dax specific conn data, non-NULL if DAX is enabled */
        struct fuse_conn_dax *dax;
 #endif
@@ -1255,7 +1264,8 @@ 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);
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 36cd03114b6d..b4b41683e97e 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -742,8 +742,12 @@ static int fuse_show_options(struct seq_file *m, struct 
dentry *root)
                        seq_printf(m, ",blksize=%lu", sb->s_blocksize);
        }
 #ifdef CONFIG_FUSE_DAX
-       if (fc->dax)
-               seq_puts(m, ",dax");
+       if (fc->dax_mode == FUSE_DAX_ALWAYS)
+               seq_puts(m, ",dax=always");
+       else if (fc->dax_mode == FUSE_DAX_NEVER)
+               seq_puts(m, ",dax=never");
+       else if (fc->dax_mode == FUSE_DAX_INODE)
+               seq_puts(m, ",dax=inode");
 #endif
 
        return 0;
@@ -1493,7 +1497,7 @@ int fuse_fill_super_common(struct super_block *sb, struct 
fuse_fs_context *ctx)
        sb->s_subtype = ctx->subtype;
        ctx->subtype = NULL;
        if (IS_ENABLED(CONFIG_FUSE_DAX)) {
-               err = fuse_dax_conn_alloc(fc, ctx->dax_dev);
+               err = fuse_dax_conn_alloc(fc, ctx->dax_mode, ctx->dax_dev);
                if (err)
                        goto err;
        }
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 0ad89c6629d7..58cfbaeb4a7d 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -88,12 +88,21 @@ struct virtio_fs_req_work {
 static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
                                 struct fuse_req *req, bool in_flight);
 
+static const struct constant_table dax_param_enums[] = {
+       {"inode",       FUSE_DAX_INODE },
+       {"always",      FUSE_DAX_ALWAYS },
+       {"never",       FUSE_DAX_NEVER },
+       {}
+};
+
 enum {
        OPT_DAX,
+       OPT_DAX_ENUM,
 };
 
 static const struct fs_parameter_spec virtio_fs_parameters[] = {
        fsparam_flag("dax", OPT_DAX),
+       fsparam_enum("dax", OPT_DAX_ENUM, dax_param_enums),
        {}
 };
 
@@ -110,7 +119,10 @@ static int virtio_fs_parse_param(struct fs_context *fsc,
 
        switch (opt) {
        case OPT_DAX:
-               ctx->dax = 1;
+               ctx->dax_mode = FUSE_DAX_ALWAYS;
+               break;
+       case OPT_DAX_ENUM:
+               ctx->dax_mode = result.uint_32;
                break;
        default:
                return -EINVAL;
@@ -1326,7 +1338,7 @@ static int virtio_fs_fill_super(struct super_block *sb, 
struct fs_context *fsc)
 
        /* virtiofs allocates and installs its own fuse devices */
        ctx->fudptr = NULL;
-       if (ctx->dax) {
+       if (ctx->dax_mode != FUSE_DAX_NEVER) {
                if (!fs->dax_dev) {
                        err = -EINVAL;
                        pr_err("virtio-fs: dax can't be enabled as filesystem"
-- 
2.27.0

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