On Thu, May 15, 2014 at 12:04 PM, Erez Zadok <[email protected]> wrote:
> Any pointers on where/how it should be supported in a stackable f/s
> would be appreciated. I’ll probably start by testing it in wrapfs
> first.
I think supporting address_space_operations->direct_IO should be
enough. This attached patch passes xfstests generic/247 which uses
O_DIRECT.
diff --git a/fs/unionfs/mmap.c b/fs/unionfs/mmap.c
index 52c7945..1c28458 100644
--- a/fs/unionfs/mmap.c
+++ b/fs/unionfs/mmap.c
@@ -18,6 +18,7 @@
*/
#include "union.h"
+#include "linux/aio.h"
/*
@@ -85,12 +86,39 @@ static int unionfs_page_mkwrite(struct
vm_area_struct *vma, struct vm_fault *vmf
return err;
}
+static ssize_t
+unionfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
+ loff_t offset, unsigned long nr_segs)
+{
+ int err = 0;
+ struct file *lower_file;
+ struct file *file = iocb->ki_filp;
+ struct inode *lower_inode;
+
+ lower_file = unionfs_lower_file(file);
+ lower_inode = file_inode(lower_file);
+ if (!lower_inode->i_mapping->a_ops ||
+ lower_inode->i_mapping->a_ops->direct_IO) {
+ printk("Underlying file doesn't support direct_IO\n");
+ err = -EINVAL;
+ goto out;
+ }
+
+ iocb->ki_filp = lower_file;
+ err = lower_inode->i_mapping->a_ops->direct_IO(rw, iocb, iov,
+ offset, nr_segs);
+ printk("direct_IO returned: %d", err);
+out:
+ return err;
+}
+
/*
* XXX: the default address_space_ops for unionfs is empty. We cannot set
* our inode->i_mapping->a_ops to NULL because too many code paths expect
* the a_ops vector to be non-NULL.
*/
struct address_space_operations unionfs_aops = {
+ .direct_IO = unionfs_direct_IO,
/* empty on purpose */
};
Vaibhav
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