On 06.07.22 10:20, Chao Peng wrote:
From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com
Implement shmem as a memfile_notifier backing store. Essentially it interacts with the memfile_notifier feature flags for userspace access/page migration/page reclaiming and implements the necessary memfile_backing_store callbacks.
Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Chao Peng chao.p.peng@linux.intel.com
[...]
+#ifdef CONFIG_MEMFILE_NOTIFIER +static struct memfile_node *shmem_lookup_memfile_node(struct file *file) +{
- struct inode *inode = file_inode(file);
- if (!shmem_mapping(inode->i_mapping))
return NULL;- return &SHMEM_I(inode)->memfile_node;
+}
+static int shmem_get_pfn(struct file *file, pgoff_t offset, pfn_t *pfn,
int *order)+{
- struct page *page;
- int ret;
- ret = shmem_getpage(file_inode(file), offset, &page, SGP_WRITE);
- if (ret)
return ret;- unlock_page(page);
- *pfn = page_to_pfn_t(page);
- *order = thp_order(compound_head(page));
- return 0;
+}
+static void shmem_put_pfn(pfn_t pfn) +{
- struct page *page = pfn_t_to_page(pfn);
- if (!page)
return;- put_page(page);
Why do we export shmem_get_pfn/shmem_put_pfn and not simply
get_folio()
and let the caller deal with putting the folio? What's the reason to
a) Operate on PFNs and not folios b) Have these get/put semantics?
+}
+static struct memfile_backing_store shmem_backing_store = {
- .lookup_memfile_node = shmem_lookup_memfile_node,
- .get_pfn = shmem_get_pfn,
- .put_pfn = shmem_put_pfn,
+}; +#endif /* CONFIG_MEMFILE_NOTIFIER */
void __init shmem_init(void) { int error; @@ -3956,6 +4059,10 @@ void __init shmem_init(void) else shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */ #endif
+#ifdef CONFIG_MEMFILE_NOTIFIER
- memfile_register_backing_store(&shmem_backing_store);
Can we instead prove a dummy function that does nothing without CONFIG_MEMFILE_NOTIFIER?
+#endif return; out1: