10 years ago commit a6849fa1f7d7 ("sysfs: Fail bin file mmap if vma close is
implemented.")
removed support for vm_ops->close() for mmap on sysfs.
As far I understand the reason is that due to the wrapping in kernfs
every VMA split operation needs to be tracked to call vm_ops->close()
for all fragments. This is not feasible with reasonable effort.
Since commit 31383c6865a5 ("mm, hugetlbfs: introduce ->split() to
vm_operations_struct")
we can get notified as soon a VMA is split, this can help to relax the
restriction.
So I propose to allow having a custom close under the condition that a
VMA cannot get split.
Signed-off-by: Richard Weinberger <[email protected]>
---
fs/kernfs/file.c | 42 ++++++++++++++++++++++++++++++++++--------
1 file changed, 34 insertions(+), 8 deletions(-)
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 06b342d8462b..82b09e72acff 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -347,6 +347,38 @@ static void kernfs_vma_open(struct vm_area_struct *vma)
kernfs_put_active(of->kn);
}
+static void kernfs_vma_close(struct vm_area_struct *vma)
+{
+ struct file *file = vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+
+ if (!of->vm_ops)
+ return;
+
+ if (!kernfs_get_active(of->kn))
+ return;
+
+ if (of->vm_ops->close)
+ of->vm_ops->close(vma);
+
+ kernfs_put_active(of->kn);
+}
+
+static int kernfs_vma_split(struct vm_area_struct *vma, unsigned long addr)
+{
+ struct file *file = vma->vm_file;
+ struct kernfs_open_file *of = kernfs_of(file);
+
+ /*
+ * We cannot keep track of split operations,
+ * so refuse splitting a VMA if someone uses close.
+ */
+ if (of->vm_ops && of->vm_ops->close)
+ return -EINVAL;
+
+ return 0;
+}
+
static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
{
struct file *file = vmf->vma->vm_file;
@@ -457,6 +489,8 @@ static struct mempolicy *kernfs_vma_get_policy(struct
vm_area_struct *vma,
static const struct vm_operations_struct kernfs_vm_ops = {
.open = kernfs_vma_open,
+ .close = kernfs_vma_close,
+ .split = kernfs_vma_split,
.fault = kernfs_vma_fault,
.page_mkwrite = kernfs_vma_page_mkwrite,
.access = kernfs_vma_access,
@@ -505,14 +539,6 @@ static int kernfs_fop_mmap(struct file *file, struct
vm_area_struct *vma)
if (of->mmapped && of->vm_ops != vma->vm_ops)
goto out_put;
- /*
- * It is not possible to successfully wrap close.
- * So error if someone is trying to use close.
- */
- rc = -EINVAL;
- if (vma->vm_ops && vma->vm_ops->close)
- goto out_put;
-
rc = 0;
of->mmapped = true;
of->vm_ops = vma->vm_ops;
--
2.26.2
