io_uring: introduce concept of memory regions

We've got a good number of mappings we share with the userspace, that
includes the main rings, provided buffer rings, upcoming rings for
zerocopy rx and more. All of them duplicate user argument parsing and
some internal details as well (page pinnning, huge page optimisations,
mmap'ing, etc.)

Introduce a notion of regions. For userspace for now it's just a new
structure called struct io_uring_region_desc which is supposed to
parameterise all such mapping / queue creations. A region either
represents a user provided chunk of memory, in which case the user_addr
field should point to it, or a request for the kernel to allocate the
memory, in which case the user would need to mmap it after using the
offset returned in the mmap_offset field. With a uniform userspace API
we can avoid additional boiler plate code and apply future optimisation
to all of them at once.

Internally, there is a new structure struct io_mapped_region holding all
relevant runtime information and some helpers to work with it. This
patch limits it to user provided regions.

Signed-off-by: Pavel Begunkov <[email protected]>
Link: https://lore.kernel.org/r/0e6fe25818dfbaebd1bd90b870a6cac503fe1a24.1731689588.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <[email protected]>

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 52a5da99a2050e1813a1b4ee3710e901c6b41ab7..1d3a37234acecfb9821d7b8724d0af0e1e3fb9f7 100644 (file)
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -75,6 +75,12 @@ struct io_hash_table {
        unsigned                hash_bits;
 };
 
+struct io_mapped_region {
+       struct page             **pages;
+       void                    *vmap_ptr;
+       size_t                  nr_pages;
+};
+
 /*
  * Arbitrary limit, can be raised if need be
  */

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 132f5db3d4e83d107a59640b4a218ea3ed2ab1dd..5cbfd330c688b515b4a4de0facd571c4057ddbbf 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -647,6 +647,20 @@ struct io_uring_files_update {
        __aligned_u64 /* __s32 * */ fds;
 };
 
+enum {
+       /* initialise with user provided memory pointed by user_addr */
+       IORING_MEM_REGION_TYPE_USER             = 1,
+};
+
+struct io_uring_region_desc {
+       __u64 user_addr;
+       __u64 size;
+       __u32 flags;
+       __u32 id;
+       __u64 mmap_offset;
+       __u64 __resv[4];
+};
+
 /*
  * Register a fully sparse file space, rather than pass in an array of all
  * -1 file descriptors.

diff --git a/io_uring/memmap.c b/io_uring/memmap.c
index 6ab59c60dfd0ac77d31c33447342584d04a31897..bbd9569a01209f8263d04a4a3804591a38ebb04e 100644 (file)
--- a/io_uring/memmap.c
+++ b/io_uring/memmap.c
@@ -12,6 +12,7 @@
 
 #include "memmap.h"
 #include "kbuf.h"
+#include "rsrc.h"
 
 static void *io_mem_alloc_compound(struct page **pages, int nr_pages,
                                   size_t size, gfp_t gfp)
@@ -194,6 +195,72 @@ void *__io_uaddr_map(struct page ***pages, unsigned short *npages,
        return ERR_PTR(-ENOMEM);
 }
 
+void io_free_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr)
+{
+       if (mr->pages) {
+               unpin_user_pages(mr->pages, mr->nr_pages);
+               kvfree(mr->pages);
+       }
+       if (mr->vmap_ptr)
+               vunmap(mr->vmap_ptr);
+       if (mr->nr_pages && ctx->user)
+               __io_unaccount_mem(ctx->user, mr->nr_pages);
+
+       memset(mr, 0, sizeof(*mr));
+}
+
+int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
+                    struct io_uring_region_desc *reg)
+{
+       int pages_accounted = 0;
+       struct page **pages;
+       int nr_pages, ret;
+       void *vptr;
+       u64 end;
+
+       if (WARN_ON_ONCE(mr->pages || mr->vmap_ptr || mr->nr_pages))
+               return -EFAULT;
+       if (memchr_inv(&reg->__resv, 0, sizeof(reg->__resv)))
+               return -EINVAL;
+       if (reg->flags != IORING_MEM_REGION_TYPE_USER)
+               return -EINVAL;
+       if (!reg->user_addr)
+               return -EFAULT;
+       if (!reg->size || reg->mmap_offset || reg->id)
+               return -EINVAL;
+       if ((reg->size >> PAGE_SHIFT) > INT_MAX)
+               return E2BIG;
+       if ((reg->user_addr | reg->size) & ~PAGE_MASK)
+               return -EINVAL;
+       if (check_add_overflow(reg->user_addr, reg->size, &end))
+               return -EOVERFLOW;
+
+       pages = io_pin_pages(reg->user_addr, reg->size, &nr_pages);
+       if (IS_ERR(pages))
+               return PTR_ERR(pages);
+
+       if (ctx->user) {
+               ret = __io_account_mem(ctx->user, nr_pages);
+               if (ret)
+                       goto out_free;
+               pages_accounted = nr_pages;
+       }
+
+       vptr = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
+       if (!vptr)
+               goto out_free;
+
+       mr->pages = pages;
+       mr->vmap_ptr = vptr;
+       mr->nr_pages = nr_pages;
+       return 0;
+out_free:
+       if (pages_accounted)
+               __io_unaccount_mem(ctx->user, pages_accounted);
+       io_pages_free(&pages, nr_pages);
+       return ret;
+}
+
 static void *io_uring_validate_mmap_request(struct file *file, loff_t pgoff,
                                            size_t sz)
 {

diff --git a/io_uring/memmap.h b/io_uring/memmap.h
index 5cec5b7ac49a45b70eea018fe5fb7c4db05fdf34..f361a635b6c7574d0bb615bb80f76c6c297b9c5c 100644 (file)
--- a/io_uring/memmap.h
+++ b/io_uring/memmap.h
@@ -22,4 +22,18 @@ unsigned long io_uring_get_unmapped_area(struct file *file, unsigned long addr,
                                         unsigned long flags);
 int io_uring_mmap(struct file *file, struct vm_area_struct *vma);
 
+void io_free_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr);
+int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
+                    struct io_uring_region_desc *reg);
+
+static inline void *io_region_get_ptr(struct io_mapped_region *mr)
+{
+       return mr->vmap_ptr;
+}
+
+static inline bool io_region_is_set(struct io_mapped_region *mr)
+{
+       return !!mr->nr_pages;
+}
+
 #endif