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io_uring/memmap: implement mmap for regions
The patch implements mmap for the param region and enables the kernel allocation mode. Internally it uses a fixed mmap offset, however the user has to use the offset returned in struct io_uring_region_desc::mmap_offset. Note, mmap doesn't and can't take ->uring_lock and the region / ring lookup is protected by ->mmap_lock, and it's directly peeking at ctx->param_region. We can't protect io_create_region() with the mmap_lock as it'd deadlock, which is why io_create_region_mmap_safe() initialises it for us in a temporary variable and then publishes it with the lock taken. It's intentionally decoupled from main region helpers, and in the future we might want to have a list of active regions, which then could be protected by the ->mmap_lock. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/0f1212bd6af7fb39b63514b34fae8948014221d1.1732886067.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov
Jens Axboe
parent
1e21df691f
commit
087f997870
3 changed files with 67 additions and 10 deletions
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@ -275,7 +275,8 @@ static int io_region_pin_pages(struct io_ring_ctx *ctx,
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static int io_region_allocate_pages(struct io_ring_ctx *ctx,
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struct io_mapped_region *mr,
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struct io_uring_region_desc *reg)
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struct io_uring_region_desc *reg,
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unsigned long mmap_offset)
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{
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gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN;
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unsigned long size = mr->nr_pages << PAGE_SHIFT;
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@ -290,8 +291,7 @@ static int io_region_allocate_pages(struct io_ring_ctx *ctx,
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p = io_mem_alloc_compound(pages, mr->nr_pages, size, gfp);
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if (!IS_ERR(p)) {
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mr->flags |= IO_REGION_F_SINGLE_REF;
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mr->pages = pages;
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return 0;
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goto done;
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}
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nr_allocated = alloc_pages_bulk_array_node(gfp, NUMA_NO_NODE,
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@ -302,12 +302,15 @@ static int io_region_allocate_pages(struct io_ring_ctx *ctx,
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kvfree(pages);
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return -ENOMEM;
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}
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done:
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reg->mmap_offset = mmap_offset;
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mr->pages = pages;
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return 0;
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}
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int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
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struct io_uring_region_desc *reg)
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struct io_uring_region_desc *reg,
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unsigned long mmap_offset)
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{
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int nr_pages, ret;
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u64 end;
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@ -341,7 +344,7 @@ int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
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if (reg->flags & IORING_MEM_REGION_TYPE_USER)
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ret = io_region_pin_pages(ctx, mr, reg);
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else
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ret = io_region_allocate_pages(ctx, mr, reg);
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ret = io_region_allocate_pages(ctx, mr, reg, mmap_offset);
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if (ret)
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goto out_free;
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@ -354,6 +357,40 @@ int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
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return ret;
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}
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int io_create_region_mmap_safe(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
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struct io_uring_region_desc *reg,
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unsigned long mmap_offset)
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{
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struct io_mapped_region tmp_mr;
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int ret;
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memcpy(&tmp_mr, mr, sizeof(tmp_mr));
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ret = io_create_region(ctx, &tmp_mr, reg, mmap_offset);
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if (ret)
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return ret;
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/*
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* Once published mmap can find it without holding only the ->mmap_lock
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* and not ->uring_lock.
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*/
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guard(mutex)(&ctx->mmap_lock);
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memcpy(mr, &tmp_mr, sizeof(tmp_mr));
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return 0;
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}
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static void *io_region_validate_mmap(struct io_ring_ctx *ctx,
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struct io_mapped_region *mr)
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{
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lockdep_assert_held(&ctx->mmap_lock);
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if (!io_region_is_set(mr))
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return ERR_PTR(-EINVAL);
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if (mr->flags & IO_REGION_F_USER_PROVIDED)
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return ERR_PTR(-EINVAL);
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return io_region_get_ptr(mr);
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}
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static void *io_uring_validate_mmap_request(struct file *file, loff_t pgoff,
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size_t sz)
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{
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@ -389,6 +426,8 @@ static void *io_uring_validate_mmap_request(struct file *file, loff_t pgoff,
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io_put_bl(ctx, bl);
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return ptr;
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}
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case IORING_MAP_OFF_PARAM_REGION:
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return io_region_validate_mmap(ctx, &ctx->param_region);
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}
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return ERR_PTR(-EINVAL);
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@ -405,6 +444,16 @@ int io_uring_mmap_pages(struct io_ring_ctx *ctx, struct vm_area_struct *vma,
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#ifdef CONFIG_MMU
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static int io_region_mmap(struct io_ring_ctx *ctx,
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struct io_mapped_region *mr,
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struct vm_area_struct *vma)
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{
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unsigned long nr_pages = mr->nr_pages;
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vm_flags_set(vma, VM_DONTEXPAND);
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return vm_insert_pages(vma, vma->vm_start, mr->pages, &nr_pages);
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}
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__cold int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
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{
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struct io_ring_ctx *ctx = file->private_data;
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@ -429,6 +478,8 @@ __cold int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
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ctx->n_sqe_pages);
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case IORING_OFF_PBUF_RING:
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return io_pbuf_mmap(file, vma);
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case IORING_MAP_OFF_PARAM_REGION:
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return io_region_mmap(ctx, &ctx->param_region, vma);
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}
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return -EINVAL;
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@ -1,6 +1,8 @@
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#ifndef IO_URING_MEMMAP_H
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#define IO_URING_MEMMAP_H
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#define IORING_MAP_OFF_PARAM_REGION 0x20000000ULL
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struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages);
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void io_pages_free(struct page ***pages, int npages);
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int io_uring_mmap_pages(struct io_ring_ctx *ctx, struct vm_area_struct *vma,
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@ -24,7 +26,13 @@ int io_uring_mmap(struct file *file, struct vm_area_struct *vma);
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void io_free_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr);
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int io_create_region(struct io_ring_ctx *ctx, struct io_mapped_region *mr,
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struct io_uring_region_desc *reg);
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struct io_uring_region_desc *reg,
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unsigned long mmap_offset);
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int io_create_region_mmap_safe(struct io_ring_ctx *ctx,
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struct io_mapped_region *mr,
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struct io_uring_region_desc *reg,
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unsigned long mmap_offset);
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static inline void *io_region_get_ptr(struct io_mapped_region *mr)
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{
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@ -588,9 +588,6 @@ static int io_register_mem_region(struct io_ring_ctx *ctx, void __user *uarg)
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rd_uptr = u64_to_user_ptr(reg.region_uptr);
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if (copy_from_user(&rd, rd_uptr, sizeof(rd)))
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return -EFAULT;
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if (!(rd.flags & IORING_MEM_REGION_TYPE_USER))
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return -EINVAL;
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if (memchr_inv(®.__resv, 0, sizeof(reg.__resv)))
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return -EINVAL;
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if (reg.flags & ~IORING_MEM_REGION_REG_WAIT_ARG)
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@ -605,7 +602,8 @@ static int io_register_mem_region(struct io_ring_ctx *ctx, void __user *uarg)
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!(ctx->flags & IORING_SETUP_R_DISABLED))
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return -EINVAL;
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ret = io_create_region(ctx, &ctx->param_region, &rd);
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ret = io_create_region_mmap_safe(ctx, &ctx->param_region, &rd,
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IORING_MAP_OFF_PARAM_REGION);
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if (ret)
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return ret;
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if (copy_to_user(rd_uptr, &rd, sizeof(rd))) {
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