io_uring: add mapping support for NOMMU archs

That is a bit weird scenario but I find it interesting to run fio loads
using LKL linux, where MMU is disabled.  Probably other real archs which
run uClinux can also benefit from this patch.

Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 4c030a92de795760242450e430b4f042bbe744c1..e6fc401e341f838152f04804beea33f6dd9f6a27 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4402,12 +4402,11 @@ static int io_uring_flush(struct file *file, void *data)
        return 0;
 }
 
-static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
+static void *io_uring_validate_mmap_request(struct file *file,
+                                           loff_t pgoff, size_t sz)
 {
-       loff_t offset = (loff_t) vma->vm_pgoff << PAGE_SHIFT;
-       unsigned long sz = vma->vm_end - vma->vm_start;
        struct io_ring_ctx *ctx = file->private_data;
-       unsigned long pfn;
+       loff_t offset = pgoff << PAGE_SHIFT;
        struct page *page;
        void *ptr;
 
@@ -4420,17 +4419,59 @@ static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
                ptr = ctx->sq_sqes;
                break;
        default:
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
        }
 
        page = virt_to_head_page(ptr);
        if (sz > page_size(page))
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
+
+       return ptr;
+}
+
+#ifdef CONFIG_MMU
+
+static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
+{
+       size_t sz = vma->vm_end - vma->vm_start;
+       unsigned long pfn;
+       void *ptr;
+
+       ptr = io_uring_validate_mmap_request(file, vma->vm_pgoff, sz);
+       if (IS_ERR(ptr))
+               return PTR_ERR(ptr);
 
        pfn = virt_to_phys(ptr) >> PAGE_SHIFT;
        return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
 }
 
+#else /* !CONFIG_MMU */
+
+static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
+{
+       return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -EINVAL;
+}
+
+static unsigned int io_uring_nommu_mmap_capabilities(struct file *file)
+{
+       return NOMMU_MAP_DIRECT | NOMMU_MAP_READ | NOMMU_MAP_WRITE;
+}
+
+static unsigned long io_uring_nommu_get_unmapped_area(struct file *file,
+       unsigned long addr, unsigned long len,
+       unsigned long pgoff, unsigned long flags)
+{
+       void *ptr;
+
+       ptr = io_uring_validate_mmap_request(file, pgoff, len);
+       if (IS_ERR(ptr))
+               return PTR_ERR(ptr);
+
+       return (unsigned long) ptr;
+}
+
+#endif /* !CONFIG_MMU */
+
 SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
                u32, min_complete, u32, flags, const sigset_t __user *, sig,
                size_t, sigsz)
@@ -4501,6 +4542,10 @@ static const struct file_operations io_uring_fops = {
        .release        = io_uring_release,
        .flush          = io_uring_flush,
        .mmap           = io_uring_mmap,
+#ifndef CONFIG_MMU
+       .get_unmapped_area = io_uring_nommu_get_unmapped_area,
+       .mmap_capabilities = io_uring_nommu_mmap_capabilities,
+#endif
        .poll           = io_uring_poll,
        .fasync         = io_uring_fasync,
 };