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* [PATCH] ovl: stacked file operation for mmap
@ 2020-10-16 15:48 Chengguang Xu
  0 siblings, 0 replies; only message in thread
From: Chengguang Xu @ 2020-10-16 15:48 UTC (permalink / raw)
  To: miklos; +Cc: linux-unionfs, root

From: root <root@localhost.localdomain>

Currently only mmap does not behave as stacked file operation,
although in practice there is less change to open a file in
RDONLY mode and take long time to do mmap but the fix looks
reasonable.

Signed-off-by: root <root@localhost.localdomain>
---
 fs/overlayfs/file.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 3582c3ae819c..f98b1c0c975b 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -461,6 +461,7 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct file *realfile = file->private_data;
 	const struct cred *old_cred;
+	struct fd real;
 	int ret;
 
 	if (!realfile->f_op->mmap)
@@ -469,7 +470,11 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 	if (WARN_ON(file != vma->vm_file))
 		return -EIO;
 
-	vma->vm_file = get_file(realfile);
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		return ret;
+
+	vma->vm_file = get_file(real.file);
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = call_mmap(vma->vm_file, vma);
@@ -477,13 +482,14 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 
 	if (ret) {
 		/* Drop reference count from new vm_file value */
-		fput(realfile);
+		fput(real.file);
 	} else {
 		/* Drop reference count from previous vm_file value */
 		fput(file);
 	}
 
 	ovl_file_accessed(file);
+	fdput(real);
 
 	return ret;
 }
-- 
2.26.2



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2020-10-16 15:48 [PATCH] ovl: stacked file operation for mmap Chengguang Xu

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