On 14.11.23 08:00, Vivek Kasireddy wrote:
For drivers that would like to longterm-pin the pages associated
with a file, the pin_user_pages_fd() API provides an option to
not only pin the pages via FOLL_PIN but also to check and migrate
them if they reside in movable zone or CMA block. This API
currently works with files that belong to either shmem or hugetlbfs.
Files belonging to other filesystems are rejected for now.
The pages need to be located first before pinning them via FOLL_PIN.
If they are found in the page cache, they can be immediately pinned.
Otherwise, they need to be allocated using the filesystem specific
APIs and then pinned.
v2:
- Drop gup_flags and improve comments and commit message (David)
- Allocate a page if we cannot find in page cache for the hugetlbfs
case as well (David)
- Don't unpin pages if there is a migration related failure (David)
- Drop the unnecessary nr_pages <= 0 check (Jason)
- Have the caller of the API pass in file * instead of fd (Jason)
v3: (David)
- Enclose the huge page allocation code with #ifdef CONFIG_HUGETLB_PAGE
(Build error reported by kernel test robot <lkp@xxxxxxxxx>)
- Don't forget memalloc_pin_restore() on non-migration related errors
- Improve the readability of the cleanup code associated with
non-migration related errors
- Augment the comments by describing FOLL_LONGTERM like behavior
- Include the R-b tag from Jason
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Cc: Dongwon Kim <dongwon.kim@xxxxxxxxx>
Cc: Junxiao Chang <junxiao.chang@xxxxxxxxx>
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> (v2)
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
---
include/linux/mm.h | 2 +
mm/gup.c | 109 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 111 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 418d26608ece..1b675fa35059 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2472,6 +2472,8 @@ long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags);
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags);
+long pin_user_pages_fd(struct file *file, pgoff_t start,
+ unsigned long nr_pages, struct page **pages);
int get_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages);
diff --git a/mm/gup.c b/mm/gup.c
index 231711efa390..b3af967cdff1 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3410,3 +3410,112 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
&locked, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages_unlocked);
+
+static struct page *alloc_file_page(struct file *file, pgoff_t idx)
+{
+#ifdef CONFIG_HUGETLB_PAGE
+ struct page *page = ERR_PTR(-ENOMEM);
+ struct folio *folio;
+ int err;
+
+ if (is_file_hugepages(file)) {
+ folio = alloc_hugetlb_folio_nodemask(hstate_file(file),
+ NUMA_NO_NODE,
+ NULL,
+ GFP_USER);
+ if (folio && folio_try_get(folio)) {
+ page = &folio->page;
+ err = hugetlb_add_to_page_cache(folio,
+ file->f_mapping,
+ idx);
+ if (err) {
+ folio_put(folio);
+ free_huge_folio(folio);
+ page = ERR_PTR(err);
+ }
+ }
+ return page;
You could avoid the "page" variable completely simply by using 3 return
statements.
LGTM, thanks
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Cheers,
David / dhildenb
