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ANDROID: sdcardfs: implement vm_ops->page_mkwrite

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This comes from wrapfs
commit 3dfec0ffe5e2 ("Wrapfs: implement vm_ops->page_mkwrite")

Some file systems (e.g., ext4) require it.  Reported by Ted Ts'o.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 34133558
Change-Id: I1a389b2422c654a6d3046bb8ec3e20511aebfa8e
This commit is contained in:
Daniel Rosenberg 2017-02-24 15:41:48 -08:00 committed by Amit Pundir
parent ba8d4d9c2f
commit d1200026c3
1 changed files with 34 additions and 0 deletions
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34
fs/sdcardfs/mmap.c
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@ -48,6 +48,39 @@ static int sdcardfs_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
return err;
}
static int sdcardfs_page_mkwrite(struct vm_area_struct *vma,
struct vm_fault *vmf)
{
int err = 0;
struct file *file, *lower_file;
const struct vm_operations_struct *lower_vm_ops;
struct vm_area_struct lower_vma;
memcpy(&lower_vma, vma, sizeof(struct vm_area_struct));
file = lower_vma.vm_file;
lower_vm_ops = SDCARDFS_F(file)->lower_vm_ops;
BUG_ON(!lower_vm_ops);
if (!lower_vm_ops->page_mkwrite)
goto out;
lower_file = sdcardfs_lower_file(file);
/*
* XXX: vm_ops->page_mkwrite may be called in parallel.
* Because we have to resort to temporarily changing the
* vma->vm_file to point to the lower file, a concurrent
* invocation of sdcardfs_page_mkwrite could see a different
* value. In this workaround, we keep a different copy of the
* vma structure in our stack, so we never expose a different
* value of the vma->vm_file called to us, even temporarily.
* A better fix would be to change the calling semantics of
* ->page_mkwrite to take an explicit file pointer.
*/
lower_vma.vm_file = lower_file;
err = lower_vm_ops->page_mkwrite(&lower_vma, vmf);
out:
return err;
}
static ssize_t sdcardfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
/*
@ -77,4 +110,5 @@ const struct address_space_operations sdcardfs_aops = {
const struct vm_operations_struct sdcardfs_vm_ops = {
.fault = sdcardfs_fault,
.page_mkwrite = sdcardfs_page_mkwrite,
};