On Wed, Jan 20, 2021 at 04:02:10PM +0000, Matthew Wilcox wrote:
On Wed, Jan 20, 2021 at 05:05:10PM +0200, Mike Rapoport wrote:
On Tue, Jan 19, 2021 at 08:22:13PM +0000, Matthew Wilcox wrote:
On Thu, Dec 03, 2020 at 08:29:44AM +0200, Mike Rapoport wrote:
+static vm_fault_t secretmem_fault(struct vm_fault *vmf) +{
- struct address_space *mapping = vmf->vma->vm_file->f_mapping;
- struct inode *inode = file_inode(vmf->vma->vm_file);
- pgoff_t offset = vmf->pgoff;
- vm_fault_t ret = 0;
- unsigned long addr;
- struct page *page;
- int err;
- if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
return vmf_error(-EINVAL);- page = find_get_page(mapping, offset);
- if (!page) {
page = secretmem_alloc_page(vmf->gfp_mask);if (!page)return vmf_error(-ENOMEM);Just use VM_FAULT_OOM directly.
Ok.
err = add_to_page_cache(page, mapping, offset, vmf->gfp_mask);if (unlikely(err))goto err_put_page;What if the error is EEXIST because somebody else raced with you to add a new page to the page cache?
Right, for -EEXIST I need a retry here, thanks.
err = set_direct_map_invalid_noflush(page, 1);if (err)goto err_del_page_cache;Does this work correctly if somebody else has a reference to the page in the meantime?
Yes, it does. If somebody else won the race that page was dropped from the direct map and this call would be essentially a nop. And anyway, the very next patch changes the way pages are removed from the direct map ;-)
What I'm thinking is:
thread A page faults doesn't find page allocates page adds page to page cache thread B page faults does find page in page cache set direct map invalid fails deletes from page cache ... ?
Hmm, this is not nice indeed...