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io_uring: get rid of remap_pfn_range() for mapping rings/sqes

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Rather than use remap_pfn_range() for this and manually free later,
switch to using vm_insert_pages() and have it Just Work.

If possible, allocate a single compound page that covers the range that
is needed. If that works, then we can just use page_address() on that
page. If we fail to get a compound page, allocate single pages and use
vmap() to map them into the kernel virtual address space.

This just covers the rings/sqes, the other remaining user of the mmap
remap_pfn_range() user will be converted separately. Once that is done,
we can kill the old alloc/free code.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2024-03-13 09:56:14 -06:00
parent 62346c6cb2
commit 3ab1db3c60
2 changed files with 133 additions and 8 deletions
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139
io_uring/io_uring.c
View file

@ -2599,6 +2599,36 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
}
static void io_pages_unmap(void *ptr, struct page ***pages,
unsigned short *npages)
{
bool do_vunmap = false;
if (!ptr)
return;
if (*npages) {
struct page **to_free = *pages;
int i;
/*
* Only did vmap for the non-compound multiple page case.
* For the compound page, we just need to put the head.
*/
if (PageCompound(to_free[0]))
*npages = 1;
else if (*npages > 1)
do_vunmap = true;
for (i = 0; i < *npages; i++)
put_page(to_free[i]);
}
if (do_vunmap)
vunmap(ptr);
kvfree(*pages);
*pages = NULL;
*npages = 0;
}
void io_mem_free(void *ptr)
{
if (!ptr)
@ -2699,8 +2729,8 @@ static void *io_sqes_map(struct io_ring_ctx *ctx, unsigned long uaddr,
static void io_rings_free(struct io_ring_ctx *ctx)
{
if (!(ctx->flags & IORING_SETUP_NO_MMAP)) {
io_mem_free(ctx->rings);
io_mem_free(ctx->sq_sqes);
io_pages_unmap(ctx->rings, &ctx->ring_pages, &ctx->n_ring_pages);
io_pages_unmap(ctx->sq_sqes, &ctx->sqe_pages, &ctx->n_sqe_pages);
} else {
io_pages_free(&ctx->ring_pages, ctx->n_ring_pages);
ctx->n_ring_pages = 0;
@ -2712,6 +2742,80 @@ static void io_rings_free(struct io_ring_ctx *ctx)
ctx->sq_sqes = NULL;
}
static void *io_mem_alloc_compound(struct page **pages, int nr_pages,
size_t size, gfp_t gfp)
{
struct page *page;
int i, order;
order = get_order(size);
if (order > MAX_PAGE_ORDER)
return ERR_PTR(-ENOMEM);
else if (order)
gfp |= __GFP_COMP;
page = alloc_pages(gfp, order);
if (!page)
return ERR_PTR(-ENOMEM);
for (i = 0; i < nr_pages; i++)
pages[i] = page + i;
return page_address(page);
}
static void *io_mem_alloc_single(struct page **pages, int nr_pages, size_t size,
gfp_t gfp)
{
void *ret;
int i;
for (i = 0; i < nr_pages; i++) {
pages[i] = alloc_page(gfp);
if (!pages[i])
goto err;
}
ret = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
if (ret)
return ret;
err:
while (i--)
put_page(pages[i]);
return ERR_PTR(-ENOMEM);
}
static void *io_pages_map(struct page ***out_pages, unsigned short *npages,
size_t size)
{
gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN;
struct page **pages;
int nr_pages;
void *ret;
nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
pages = kvmalloc_array(nr_pages, sizeof(struct page *), gfp);
if (!pages)
return ERR_PTR(-ENOMEM);
ret = io_mem_alloc_compound(pages, nr_pages, size, gfp);
if (!IS_ERR(ret))
goto done;
ret = io_mem_alloc_single(pages, nr_pages, size, gfp);
if (!IS_ERR(ret)) {
done:
*out_pages = pages;
*npages = nr_pages;
return ret;
}
kvfree(pages);
*out_pages = NULL;
*npages = 0;
return ret;
}
void *io_mem_alloc(size_t size)
{
gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP;
@ -3298,14 +3402,12 @@ static void *io_uring_validate_mmap_request(struct file *file,
/* Don't allow mmap if the ring was setup without it */
if (ctx->flags & IORING_SETUP_NO_MMAP)
return ERR_PTR(-EINVAL);
ptr = ctx->rings;
break;
return ctx->rings;
case IORING_OFF_SQES:
/* Don't allow mmap if the ring was setup without it */
if (ctx->flags & IORING_SETUP_NO_MMAP)
return ERR_PTR(-EINVAL);
ptr = ctx->sq_sqes;
break;
return ctx->sq_sqes;
case IORING_OFF_PBUF_RING: {
struct io_buffer_list *bl;
unsigned int bgid;
@ -3329,11 +3431,22 @@ static void *io_uring_validate_mmap_request(struct file *file,
return ptr;
}
int io_uring_mmap_pages(struct io_ring_ctx *ctx, struct vm_area_struct *vma,
struct page **pages, int npages)
{
unsigned long nr_pages = npages;
vm_flags_set(vma, VM_DONTEXPAND);
return vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
}
#ifdef CONFIG_MMU
static __cold int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
{
struct io_ring_ctx *ctx = file->private_data;
size_t sz = vma->vm_end - vma->vm_start;
long offset = vma->vm_pgoff << PAGE_SHIFT;
unsigned long pfn;
void *ptr;
@ -3341,6 +3454,16 @@ static __cold int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
if (IS_ERR(ptr))
return PTR_ERR(ptr);
switch (offset & IORING_OFF_MMAP_MASK) {
case IORING_OFF_SQ_RING:
case IORING_OFF_CQ_RING:
return io_uring_mmap_pages(ctx, vma, ctx->ring_pages,
ctx->n_ring_pages);
case IORING_OFF_SQES:
return io_uring_mmap_pages(ctx, vma, ctx->sqe_pages,
ctx->n_sqe_pages);
}
pfn = virt_to_phys(ptr) >> PAGE_SHIFT;
return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
}
@ -3630,7 +3753,7 @@ static __cold int io_allocate_scq_urings(struct io_ring_ctx *ctx,
return -EOVERFLOW;
if (!(ctx->flags & IORING_SETUP_NO_MMAP))
rings = io_mem_alloc(size);
rings = io_pages_map(&ctx->ring_pages, &ctx->n_ring_pages, size);
else
rings = io_rings_map(ctx, p->cq_off.user_addr, size);
@ -3655,7 +3778,7 @@ static __cold int io_allocate_scq_urings(struct io_ring_ctx *ctx,
}
if (!(ctx->flags & IORING_SETUP_NO_MMAP))
ptr = io_mem_alloc(size);
ptr = io_pages_map(&ctx->sqe_pages, &ctx->n_sqe_pages, size);
else
ptr = io_sqes_map(ctx, p->sq_off.user_addr, size);

2
io_uring/io_uring.h
View file

@ -70,6 +70,8 @@ bool io_req_post_cqe(struct io_kiocb *req, s32 res, u32 cflags);
void __io_commit_cqring_flush(struct io_ring_ctx *ctx);
struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages);
int io_uring_mmap_pages(struct io_ring_ctx *ctx, struct vm_area_struct *vma,
struct page **pages, int npages);
struct file *io_file_get_normal(struct io_kiocb *req, int fd);
struct file *io_file_get_fixed(struct io_kiocb *req, int fd,