On 2024/5/9 8:44, Randy Dunlap wrote:

quoted

 
+/**
+ * page_frag_cache_is_pfmemalloc() - Check for pfmemalloc.
+ * @nc: page_frag cache from which to check
+ *
+ * Used to check if the current page in page_frag cache is pfmemalloc'ed.
+ * It has the same calling context expection as the alloc API.
+ *
+ * Return:
+ * Return true if the current page in page_frag cache is pfmemalloc'ed,

Drop the (second) word "Return"...

Did you mean something like below:

* Return:
* Return true if the current page in page_frag cache is pfmemalloc'ed,
* otherwise false.

Or:

* Return:
* true if the current page in page_frag cache is pfmemalloc'ed, otherwise
* return false.

quoted

+ * otherwise return false.
+ */
 static inline bool page_frag_cache_is_pfmemalloc(struct page_frag_cache *nc)
 {
 	return encoded_page_pfmemalloc(nc->encoded_va);

@@ -92,6 +109,19 @@ void *__page_frag_alloc_va_align(struct page_frag_cache *nc,
 				 unsigned int fragsz, gfp_t gfp_mask,
 				 unsigned int align_mask);
 
+/**
+ * page_frag_alloc_va_align() - Alloc a page fragment with aligning requirement.
+ * @nc: page_frag cache from which to allocate
+ * @fragsz: the requested fragment size
+ * @gfp_mask: the allocation gfp to use when cache need to be refilled

                                                      needs

quoted

+ * @align: the requested aligning requirement for 'va'

                 or                                  @va

What does the 'or' means?

...

                                                 needs

quoted

+ *
+ * Prepare a page fragment with minimum size of ‘fragsz’, 'fragsz' is also used

                                                   'fragsz'. 'fragsz'
(don't use fancy single quote marks)

You mean using @parameter to replace all the parameters marked with single
quote marks, right?

...

quoted

 
+/**
+ * page_frag_alloc_prepare - Prepare allocing a page fragment.
+ * @nc: page_frag cache from which to prepare
+ * @offset: out as the offset of the page fragment
+ * @fragsz: in as the requested size, out as the available size
+ * @va: out as the virtual address of the returned page fragment
+ * @gfp: the allocation gfp to use when cache need to be refilled
+ *
+ * Prepare a page fragment with minimum size of ‘fragsz’, 'fragsz' is also used

                                                   'fragsz'. 'fragsz'
(don't use fancy single quote marks)

You could also (in several places) refer to the variables as
                                                    @fragsz. @fragsz

quoted

+ * to report the maximum size of the page fragment. Return both 'page' and 'va'
+ * of the fragment to the caller.
+ *
+ * Return:
+ * Return the page fragment, otherwise return NULL.

Drop second "Return". But the paragraph above says that both @page and @va
are returned. How is that done?

struct page *page_frag_alloc_prepare(struct page_frag_cache *nc,
				     unsigned int *offset,
				     unsigned int *fragsz,
				     void **va, gfp_t gfp);

As above, @page is returned through the function return, @va is returned
through double pointer.

Thanks for the detailed review.