On 6/11/24 11:27 AM, Martin Oliveira wrote:
The .page_mkwrite operator of kernfs just calls file_update_time().
This is the same behaviour that the fault code does if .page_mkwrite is
not set.
Furthermore, having the page_mkwrite() operator causes
writable_file_mapping_allowed() to fail due to
vma_needs_dirty_tracking() on the gup flow, which is a pre-requisite for
enabling P2PDMA over RDMA.
There are no users of .page_mkwrite and no known valid use cases, so
just remove the .page_mkwrite from kernfs_ops and return -EINVAL if an
mmap() implementation sets .page_mkwrite.
Hi Martin and Logan!
First of all, I admire this approach to solving one of the gup+filesystem
interaction problems, by coming in from the other direction. Neat. :)
Co-developed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Martin Oliveira <martin.oliveira@xxxxxxxxxxxxx>
---
fs/kernfs/file.c | 26 +++-----------------------
1 file changed, 3 insertions(+), 23 deletions(-)
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 8502ef68459b9..a198cb0718772 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -386,28 +386,6 @@ static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
return ret;
}
-static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
-{
- struct file *file = vmf->vma->vm_file;
- struct kernfs_open_file *of = kernfs_of(file);
- vm_fault_t ret;
-
- if (!of->vm_ops)
- return VM_FAULT_SIGBUS;
-
- if (!kernfs_get_active(of->kn))
- return VM_FAULT_SIGBUS;
-
- ret = 0;
- if (of->vm_ops->page_mkwrite)
- ret = of->vm_ops->page_mkwrite(vmf);
- else
- file_update_time(file);
-
- kernfs_put_active(of->kn);
- return ret;
-}
-
static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
void *buf, int len, int write)
{
@@ -432,7 +410,6 @@ static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
static const struct vm_operations_struct kernfs_vm_ops = {
.open = kernfs_vma_open,
.fault = kernfs_vma_fault,
- .page_mkwrite = kernfs_vma_page_mkwrite,
.access = kernfs_vma_access,
};
@@ -482,6 +459,9 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
if (vma->vm_ops && vma->vm_ops->close)
goto out_put;
+ if (vma->vm_ops->page_mkwrite)
As the kernel test bot results imply, you probably want to do it like this:
if (vma->vm_ops && vma->vm_ops->page_mkwrite)
+ goto out_put;
+
rc = 0;
if (!of->mmapped) {
of->mmapped = true;
thanks,
--
John Hubbard
NVIDIA
