io_uring/memmap: add IO_REGION_F_SINGLE_REF

Kernel allocated compound pages will have just one reference for the
entire page array, add a flag telling io_free_region about that.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a7abfa7535e9728d5fcade29a1ea1605ec2c04ce.1732886067.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/memmap.c b/io_uring/memmap.c
index 5d261e07c2e32cb1378ac749d0dcd907415fbbc6..a37ccb167258c5ffc63c4e33af4954f36ad7316a 100644 (file)
--- a/io_uring/memmap.c
+++ b/io_uring/memmap.c
@@ -207,15 +207,23 @@ enum {
        IO_REGION_F_VMAP                        = 1,
        /* memory is provided by user and pinned by the kernel */
        IO_REGION_F_USER_PROVIDED               = 2,
+       /* only the first page in the array is ref'ed */
+       IO_REGION_F_SINGLE_REF                  = 4,
 };
 
 void io_free_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr)
 {
        if (mr->pages) {
+               long nr_refs = mr->nr_pages;
+
+               if (mr->flags & IO_REGION_F_SINGLE_REF)
+                       nr_refs = 1;
+
                if (mr->flags & IO_REGION_F_USER_PROVIDED)
-                       unpin_user_pages(mr->pages, mr->nr_pages);
+                       unpin_user_pages(mr->pages, nr_refs);
                else
-                       release_pages(mr->pages, mr->nr_pages);
+                       release_pages(mr->pages, nr_refs);
+
                kvfree(mr->pages);
        }
        if ((mr->flags & IO_REGION_F_VMAP) && mr->ptr)