When the per inode DAX hint changes while the file is still *opened*, it
is quite complicated and maybe fragile to dynamically change the DAX
state.

Hence mark the inode and corresponding dentries as DONE_CACHE once the
per inode DAX hint changes, so that the inode instance will be evicted
and freed as soon as possible once the file is closed and the last
reference to the inode is put. And then when the file gets reopened next
time, the new instantiated inode will reflect the new DAX state.

In summary, when the per inode DAX hint changes for an *opened* file, the
DAX state of the file won't be updated until this file is closed and
reopened later.

Signed-off-by: Jeffle Xu <[email protected]>
---
 fs/fuse/dax.c    | 9 +++++++++
 fs/fuse/fuse_i.h | 1 +
 fs/fuse/inode.c  | 3 +++
 3 files changed, 13 insertions(+)

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index c8ee601b94b8..e8766420c708 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -1362,6 +1362,15 @@ void fuse_dax_inode_init(struct inode *inode, unsigned 
int flags)
        inode->i_data.a_ops = &fuse_dax_file_aops;
 }
 
+void fuse_dax_dontcache(struct inode *inode, unsigned int flags)
+{
+       struct fuse_conn *fc = get_fuse_conn(inode);
+
+       if (fuse_is_inode_dax_mode(fc->dax_mode) &&
+           (!!IS_DAX(inode) != !!(flags & FUSE_ATTR_DAX)))
+               d_mark_dontcache(inode);
+}
+
 bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment)
 {
        if (fc->dax && (map_alignment > FUSE_DAX_SHIFT)) {
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 58e54b5a4d65..fe8364b522ac 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1282,6 +1282,7 @@ 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, unsigned int flags);
 void fuse_dax_inode_cleanup(struct inode *inode);
+void fuse_dax_dontcache(struct inode *inode, unsigned int flags);
 bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int 
map_alignment);
 void fuse_dax_cancel_work(struct fuse_conn *fc);
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 0512d8cb36c3..4a2a58cc71af 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -268,6 +268,9 @@ void fuse_change_attributes(struct inode *inode, struct 
fuse_attr *attr,
                if (inval)
                        invalidate_inode_pages2(inode->i_mapping);
        }
+
+       if (IS_ENABLED(CONFIG_FUSE_DAX))
+               fuse_dax_dontcache(inode, attr->flags);
 }
 
 static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
-- 
2.27.0

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