Address the TODO comment in fuse_dax_read_iter() which has been present
since the initial DAX implementation in commit c2d0ad00d948 ("virtiofs:
implement dax read/write operations").

Simply calling file_accessed() is insufficient for FUSE, as it only
updates the local inode without notifying the server.

This patch introduces fuse_flush_atime() to explicitly send atime
updates to the server via SETATTR, followed by fuse_invalidate_atime()
to invalidate the attribute cache.

Signed-off-by: Yuto Ohnuki <ytohnuki@amazon.com>
---
 fs/fuse/dax.c    |  4 +++-
 fs/fuse/dir.c    | 20 ++++++++++++++++++++
 fs/fuse/fuse_i.h |  1 +
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index ac6d4c1064cc..da7aa60c308a 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -688,7 +688,9 @@ ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	ret = dax_iomap_rw(iocb, to, &fuse_iomap_ops);
 	inode_unlock_shared(inode);
 
-	/* TODO file_accessed(iocb->f_filp) */
+	file_accessed(iocb->ki_filp);
+	fuse_flush_atime(inode);
+	fuse_invalidate_atime(inode);
 	return ret;
 }
 
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 4b6b3d2758ff..a919dc1ac6bc 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -2113,6 +2113,26 @@ int fuse_flush_times(struct inode *inode, struct fuse_file *ff)
 	return fuse_simple_request(fm, &args);
 }
 
+/*
+ * Flush inode->i_atime to the server
+ */
+int fuse_flush_atime(struct inode *inode)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_setattr_in inarg;
+	struct fuse_attr_out outarg;
+
+	memset(&inarg, 0, sizeof(inarg));
+	memset(&outarg, 0, sizeof(outarg));
+
+	inarg.valid = FATTR_ATIME | FATTR_ATIME_NOW;
+
+	fuse_setattr_fill(fm->fc, &args, inode, &inarg, &outarg);
+
+	return fuse_simple_request(fm, &args);
+}
+
 /*
  * Set attributes, and at the same time refresh them.
  *
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 7f16049387d1..553195ce707f 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1467,6 +1467,7 @@ int fuse_dev_release(struct inode *inode, struct file *file);
 bool fuse_write_update_attr(struct inode *inode, loff_t pos, ssize_t written);
 
 int fuse_flush_times(struct inode *inode, struct fuse_file *ff);
+int fuse_flush_atime(struct inode *inode);
 int fuse_write_inode(struct inode *inode, struct writeback_control *wbc);
 
 int fuse_do_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
-- 
2.50.1




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