On 2024/5/10 0:58, Mat Martineau wrote:

...

quoted

+/**
+ * page_frag_alloc_probe - Probe the avaiable page fragment.
+ * @nc: page_frag cache from which to probe
+ * @offset: out as the offset of the page fragment
+ * @fragsz: in as the requested size, out as the available size

Hi Yunsheng -

fragsz is never used as an input in this function. I think it would be good to make the code consistent with this documentation by checking that *fragsz <= (nc)->remaining

Yes, you are right.
It is not used as input, will update the documentation according.

quoted

+ * @va: out as the virtual address of the returned page fragment
+ *
+ * Probe the current available memory to caller without doing cache refilling.
+ * If the cache is empty, return NULL.

Instead of this line, is it more accurate to say "if no space is available in the page_frag cache, return NULL" ?

I also suggest adding some documentation here like:

"If the requested space is available, up to fragsz bytes may be added to the fragment using page_frag_alloc_commit()".

Ok.

quoted

+ *
+ * Return:
+ * Return the page fragment, otherwise return NULL.
+ */
#define page_frag_alloc_probe(nc, offset, fragsz, va)            \
({                                    \
    struct encoded_va *__encoded_va;                \

@@ -162,6 +241,13 @@ static inline struct encoded_va *__page_frag_alloc_probe(struct page_frag_cache
    __page;                                \

})

+/**
+ * page_frag_alloc_commit - Commit allocing a page fragment.
+ * @nc: page_frag cache from which to commit
+ * @fragsz: size of the page fragment has been used
+ *
+ * Commit the alloc preparing by passing the actual used size.

Rephrasing suggestion:

"Commit the actual used size for the allocation that was either prepared or probed"

Ok.

Thanks.

Thanks,

Mat