Commit 6e73dffb authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: let to set a range for file slot allocation 



From recently io_uring provides an option to allocate a file index for
operation registering fixed files. However, it's utterly unusable with
mixed approaches when for a part of files the userspace knows better
where to place it, as it may race and users don't have any sane way to
pick a slot and hoping it will not be taken.

Let the userspace to register a range of fixed file slots in which the
auto-allocation happens. The use case is splittting the fixed table in
two parts, where on of them is used for auto-allocation and another for
slot-specified operations.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/66ab0394e436f38437cf7c44676e1920d09687ad.1656154403.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent e6130eba

include/linux/io_uring_types.h

+3 −0
Original line number Original line Diff line number Diff line
@@ -233,6 +233,9 @@ struct io_ring_ctx { 




	unsigned long		check_cq;

	unsigned long		check_cq;





	unsigned int		file_alloc_start;

	unsigned int		file_alloc_end;



	struct {

	struct {

		/*

		/*

		 * We cache a range of free CQEs we can use, once exhausted it

		 * We cache a range of free CQEs we can use, once exhausted it

include/uapi/linux/io_uring.h

+13 −0
Original line number Original line Diff line number Diff line
@@ -449,6 +449,9 @@ enum { 
	/* sync cancelation API */

	/* sync cancelation API */

	IORING_REGISTER_SYNC_CANCEL		= 24,

	IORING_REGISTER_SYNC_CANCEL		= 24,





	/* register a range of fixed file slots for automatic slot allocation */

	IORING_REGISTER_FILE_ALLOC_RANGE	= 25,



	/* this goes last */

	/* this goes last */

	IORING_REGISTER_LAST

	IORING_REGISTER_LAST

};

};
@@ -595,4 +598,14 @@ struct io_uring_sync_cancel_reg { 
	__u64				pad[4];

	__u64				pad[4];

};

};





/*

 * Argument for IORING_REGISTER_FILE_ALLOC_RANGE

 * The range is specified as [off, off + len)

 */

struct io_uring_file_index_range {

	__u32	off;

	__u32	len;

	__u64	resv;

};



#endif
 
#endif

io_uring/filetable.c

+20 −4
Original line number Original line Diff line number Diff line
@@ -16,7 +16,7 @@ 
static int io_file_bitmap_get(struct io_ring_ctx *ctx)

static int io_file_bitmap_get(struct io_ring_ctx *ctx)

{

{

	struct io_file_table *table = &ctx->file_table;

	struct io_file_table *table = &ctx->file_table;

	unsigned long nr = ctx->nr_user_files;

	unsigned long nr = ctx->file_alloc_end;

	int ret;

	int ret;





	do {

	do {
@@ -24,11 +24,10 @@ static int io_file_bitmap_get(struct io_ring_ctx *ctx) 
		if (ret != nr)

		if (ret != nr)

			return ret;

			return ret;





		if (!table->alloc_hint)

		if (table->alloc_hint == ctx->file_alloc_start)

			break;

			break;



		nr = table->alloc_hint;

		nr = table->alloc_hint;

		table->alloc_hint = 0;

		table->alloc_hint = ctx->file_alloc_start;

	} while (1);

	} while (1);





	return -ENFILE;

	return -ENFILE;
@@ -175,3 +174,20 @@ int io_fixed_fd_remove(struct io_ring_ctx *ctx, unsigned int offset) 
	io_rsrc_node_switch(ctx, ctx->file_data);

	io_rsrc_node_switch(ctx, ctx->file_data);

	return 0;

	return 0;

}

}



int io_register_file_alloc_range(struct io_ring_ctx *ctx,

				 struct io_uring_file_index_range __user *arg)

{

	struct io_uring_file_index_range range;

	u32 end;



	if (copy_from_user(&range, arg, sizeof(range)))

		return -EFAULT;

	if (check_add_overflow(range.off, range.len, &end))

		return -EOVERFLOW;

	if (range.resv || end > ctx->nr_user_files)

		return -EINVAL;



	io_file_table_set_alloc_range(ctx, range.off, range.len);

	return 0;

}

io_uring/filetable.h

+17 −3
Original line number Original line Diff line number Diff line
@@ -3,9 +3,7 @@ 
#define IOU_FILE_TABLE_H

#define IOU_FILE_TABLE_H





#include <linux/file.h>

#include <linux/file.h>



#include <linux/io_uring_types.h>

struct io_ring_ctx;

struct io_kiocb;





/*

/*

 * FFS_SCM is only available on 64-bit archs, for 32-bit we just define it as 0

 * FFS_SCM is only available on 64-bit archs, for 32-bit we just define it as 0
@@ -33,6 +31,9 @@ int __io_fixed_fd_install(struct io_ring_ctx *ctx, struct file *file, 
				unsigned int file_slot);

				unsigned int file_slot);

int io_fixed_fd_remove(struct io_ring_ctx *ctx, unsigned int offset);

int io_fixed_fd_remove(struct io_ring_ctx *ctx, unsigned int offset);





int io_register_file_alloc_range(struct io_ring_ctx *ctx,

				 struct io_uring_file_index_range __user *arg);



unsigned int io_file_get_flags(struct file *file);

unsigned int io_file_get_flags(struct file *file);





static inline void io_file_bitmap_clear(struct io_file_table *table, int bit)

static inline void io_file_bitmap_clear(struct io_file_table *table, int bit)
@@ -71,4 +72,17 @@ static inline void io_fixed_file_set(struct io_fixed_file *file_slot, 
	file_slot->file_ptr = file_ptr;

	file_slot->file_ptr = file_ptr;

}

}





static inline void io_reset_alloc_hint(struct io_ring_ctx *ctx)

{

	ctx->file_table.alloc_hint = ctx->file_alloc_start;

}



static inline void io_file_table_set_alloc_range(struct io_ring_ctx *ctx,

						 unsigned off, unsigned len)

{

	ctx->file_alloc_start = off;

	ctx->file_alloc_end = off + len;

	io_reset_alloc_hint(ctx);

}



#endif
 
#endif

io_uring/io_uring.c

+6 −0
Original line number Original line Diff line number Diff line
@@ -3866,6 +3866,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, 
			break;

			break;

		ret = io_sync_cancel(ctx, arg);

		ret = io_sync_cancel(ctx, arg);

		break;

		break;

	case IORING_REGISTER_FILE_ALLOC_RANGE:

		ret = -EINVAL;

		if (!arg || nr_args)

			break;

		ret = io_register_file_alloc_range(ctx, arg);

		break;

	default:

	default:

		ret = -EINVAL;

		ret = -EINVAL;

		break;

		break;