On 2/3/21 2:00 PM, Joao Martins wrote:
Add a unpin_user_page_range() API which takes a starting page
and how many consecutive pages we want to dirty.
Given that we won't be iterating on a list of changes, change
compound_next() to receive a bool, whether to calculate from the starting
page, or walk the page array. Finally add a separate iterator,
A bool arg is sometimes, but not always, a hint that you really just want
a separate set of routines. Below...
for_each_compound_range() that just operate in page ranges as opposed
to page array.
For users (like RDMA mr_dereg) where each sg represents a
contiguous set of pages, we're able to more efficiently unpin
pages without having to supply an array of pages much of what
happens today with unpin_user_pages().
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
---
include/linux/mm.h | 2 ++
mm/gup.c | 48 ++++++++++++++++++++++++++++++++++++++--------
2 files changed, 42 insertions(+), 8 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a608feb0d42e..b76063f7f18a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1265,6 +1265,8 @@ static inline void put_page(struct page *page)
void unpin_user_page(struct page *page);
void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
bool make_dirty);
+void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
+ bool make_dirty);
void unpin_user_pages(struct page **pages, unsigned long npages);
/**
diff --git a/mm/gup.c b/mm/gup.c
index 971a24b4b73f..1b57355d5033 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -215,11 +215,16 @@ void unpin_user_page(struct page *page)
}
EXPORT_SYMBOL(unpin_user_page);
-static inline unsigned int count_ntails(struct page **pages, unsigned long npages)
+static inline unsigned int count_ntails(struct page **pages,
+ unsigned long npages, bool range)
{
- struct page *head = compound_head(pages[0]);
+ struct page *page = pages[0], *head = compound_head(page);
unsigned int ntails;
+ if (range)
+ return (!PageCompound(head) || compound_order(head) <= 1) ? 1 :
+ min_t(unsigned int, (head + compound_nr(head) - page), npages);
Here, you clearly should use a separate set of _range routines. Because you're basically
creating two different routines here! Keep it simple.
Once you're in a separate routine, you might feel more comfortable expanding that to
a more readable form, too:
if (!PageCompound(head) || compound_order(head) <= 1)
return 1;
return min_t(unsigned int, (head + compound_nr(head) - page), npages);
thanks,
--
John Hubbard
NVIDIA
+
for (ntails = 1; ntails < npages; ntails++) {
if (compound_head(pages[ntails]) != head)
break;
@@ -229,20 +234,32 @@ static inline unsigned int count_ntails(struct page **pages, unsigned long npage
}
static inline void compound_next(unsigned long i, unsigned long npages,
- struct page **list, struct page **head,
- unsigned int *ntails)
+ struct page **list, bool range,
+ struct page **head, unsigned int *ntails)
{
+ struct page *p, **next = &p;
+
if (i >= npages)
return;
- *ntails = count_ntails(list + i, npages - i);
- *head = compound_head(list[i]);
+ if (range)
+ *next = *list + i;
+ else
+ next = list + i;
+
+ *ntails = count_ntails(next, npages - i, range);
+ *head = compound_head(*next);
}
+#define for_each_compound_range(i, list, npages, head, ntails) \
+ for (i = 0, compound_next(i, npages, list, true, &head, &ntails); \
+ i < npages; i += ntails, \
+ compound_next(i, npages, list, true, &head, &ntails))
+
#define for_each_compound_head(i, list, npages, head, ntails) \
- for (i = 0, compound_next(i, npages, list, &head, &ntails); \
+ for (i = 0, compound_next(i, npages, list, false, &head, &ntails); \
i < npages; i += ntails, \
- compound_next(i, npages, list, &head, &ntails))
+ compound_next(i, npages, list, false, &head, &ntails))
/**
* unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages
@@ -306,6 +323,21 @@ void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages,
}
EXPORT_SYMBOL(unpin_user_pages_dirty_lock);
+void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
+ bool make_dirty)
+{
+ unsigned long index;
+ struct page *head;
+ unsigned int ntails;
+
+ for_each_compound_range(index, &page, npages, head, ntails) {
+ if (make_dirty && !PageDirty(head))
+ set_page_dirty_lock(head);
+ put_compound_head(head, ntails, FOLL_PIN);
+ }
+}
+EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
+
/**
* unpin_user_pages() - release an array of gup-pinned pages.
* @pages: array of pages to be marked dirty and released.
