io_uring/memmap: optimise single folio regions

We don't need to vmap if memory is already physically contiguous. There
are two important cases it covers: PAGE_SIZE regions and huge pages.
Use io_check_coalesce_buffer() to get the number of contiguous folios.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d5240af23064a824c29d14d2406f1ae764bf4505.1732886067.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 96c4f6b6117171f82711ab6dfda642c24f612406..fd348c98f64fa97d859c72b1aca5c6848cfbe471 100644 (file)
--- a/io_uring/memmap.c
+++ b/io_uring/memmap.c
@@ -226,12 +226,31 @@ void io_free_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr)
        memset(mr, 0, sizeof(*mr));
 }
 
+static int io_region_init_ptr(struct io_mapped_region *mr)
+{
+       struct io_imu_folio_data ifd;
+       void *ptr;
+
+       if (io_check_coalesce_buffer(mr->pages, mr->nr_pages, &ifd)) {
+               if (ifd.nr_folios == 1) {
+                       mr->ptr = page_address(mr->pages[0]);
+                       return 0;
+               }
+       }
+       ptr = vmap(mr->pages, mr->nr_pages, VM_MAP, PAGE_KERNEL);
+       if (!ptr)
+               return -ENOMEM;
+
+       mr->ptr = ptr;
+       mr->flags |= IO_REGION_F_VMAP;
+       return 0;
+}
+
 int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
                     struct io_uring_region_desc *reg)
 {
        struct page **pages;
        int nr_pages, ret;
-       void *vptr;
        u64 end;
 
        if (WARN_ON_ONCE(mr->pages || mr->ptr || mr->nr_pages))
@@ -267,13 +286,9 @@ int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
        mr->pages = pages;
        mr->flags |= IO_REGION_F_USER_PROVIDED;
 
-       vptr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
-       if (!vptr) {
-               ret = -ENOMEM;
+       ret = io_region_init_ptr(mr);
+       if (ret)
                goto out_free;
-       }
-       mr->ptr = vptr;
-       mr->flags |= IO_REGION_F_VMAP;
        return 0;
 out_free:
        io_free_region(ctx, mr);