[Virtio-fs] [PATCH v4 6/8] fuse: mark inode DONT_CACHE when per-file DAX indication changes

[Jeffle Xu]

When the per-file DAX indication 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-file DAX indication 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 inode will reflect the new DAX state.

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

Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
---
 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 30833f8d37dd..f7ede0be4e00 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -1364,6 +1364,15 @@ 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, bool newdax)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (fc->dax_mode == FUSE_DAX_INODE &&
+	    fc->perfile_dax && (!!IS_DAX(inode) != newdax))
+		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 7b7b4c208af2..56fe1c4d2136 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1260,6 +1260,7 @@ 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, bool newdax);
 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 8080f78befed..8c9774c6a210 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -269,6 +269,9 @@ 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 & FUSE_ATTR_DAX);
 }
 
 static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
-- 
2.27.0