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![Pavel Begunkov](/assets/img/avatar_default.png)
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: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/66ab0394e436f38437cf7c44676e1920d09687ad.1656154403.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
193 lines
4.4 KiB
C
193 lines
4.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/file.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/nospec.h>
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#include <linux/io_uring.h>
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#include <uapi/linux/io_uring.h>
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#include "io_uring.h"
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#include "rsrc.h"
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#include "filetable.h"
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static int io_file_bitmap_get(struct io_ring_ctx *ctx)
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{
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struct io_file_table *table = &ctx->file_table;
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unsigned long nr = ctx->file_alloc_end;
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int ret;
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do {
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ret = find_next_zero_bit(table->bitmap, nr, table->alloc_hint);
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if (ret != nr)
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return ret;
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if (table->alloc_hint == ctx->file_alloc_start)
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break;
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nr = table->alloc_hint;
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table->alloc_hint = ctx->file_alloc_start;
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} while (1);
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return -ENFILE;
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}
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bool io_alloc_file_tables(struct io_file_table *table, unsigned nr_files)
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{
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table->files = kvcalloc(nr_files, sizeof(table->files[0]),
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GFP_KERNEL_ACCOUNT);
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if (unlikely(!table->files))
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return false;
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table->bitmap = bitmap_zalloc(nr_files, GFP_KERNEL_ACCOUNT);
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if (unlikely(!table->bitmap)) {
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kvfree(table->files);
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return false;
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}
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return true;
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}
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void io_free_file_tables(struct io_file_table *table)
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{
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kvfree(table->files);
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bitmap_free(table->bitmap);
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table->files = NULL;
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table->bitmap = NULL;
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}
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static int io_install_fixed_file(struct io_ring_ctx *ctx, struct file *file,
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u32 slot_index)
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__must_hold(&req->ctx->uring_lock)
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{
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bool needs_switch = false;
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struct io_fixed_file *file_slot;
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int ret;
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if (io_is_uring_fops(file))
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return -EBADF;
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if (!ctx->file_data)
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return -ENXIO;
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if (slot_index >= ctx->nr_user_files)
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return -EINVAL;
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slot_index = array_index_nospec(slot_index, ctx->nr_user_files);
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file_slot = io_fixed_file_slot(&ctx->file_table, slot_index);
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if (file_slot->file_ptr) {
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struct file *old_file;
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ret = io_rsrc_node_switch_start(ctx);
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if (ret)
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goto err;
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old_file = (struct file *)(file_slot->file_ptr & FFS_MASK);
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ret = io_queue_rsrc_removal(ctx->file_data, slot_index,
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ctx->rsrc_node, old_file);
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if (ret)
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goto err;
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file_slot->file_ptr = 0;
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io_file_bitmap_clear(&ctx->file_table, slot_index);
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needs_switch = true;
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}
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ret = io_scm_file_account(ctx, file);
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if (!ret) {
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*io_get_tag_slot(ctx->file_data, slot_index) = 0;
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io_fixed_file_set(file_slot, file);
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io_file_bitmap_set(&ctx->file_table, slot_index);
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}
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err:
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if (needs_switch)
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io_rsrc_node_switch(ctx, ctx->file_data);
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if (ret)
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fput(file);
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return ret;
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}
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int __io_fixed_fd_install(struct io_ring_ctx *ctx, struct file *file,
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unsigned int file_slot)
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{
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bool alloc_slot = file_slot == IORING_FILE_INDEX_ALLOC;
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int ret;
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if (alloc_slot) {
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ret = io_file_bitmap_get(ctx);
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if (unlikely(ret < 0))
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return ret;
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file_slot = ret;
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} else {
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file_slot--;
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}
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ret = io_install_fixed_file(ctx, file, file_slot);
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if (!ret && alloc_slot)
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ret = file_slot;
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return ret;
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}
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/*
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* Note when io_fixed_fd_install() returns error value, it will ensure
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* fput() is called correspondingly.
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*/
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int io_fixed_fd_install(struct io_kiocb *req, unsigned int issue_flags,
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struct file *file, unsigned int file_slot)
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{
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struct io_ring_ctx *ctx = req->ctx;
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int ret;
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io_ring_submit_lock(ctx, issue_flags);
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ret = __io_fixed_fd_install(ctx, file, file_slot);
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io_ring_submit_unlock(ctx, issue_flags);
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if (unlikely(ret < 0))
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fput(file);
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return ret;
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}
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int io_fixed_fd_remove(struct io_ring_ctx *ctx, unsigned int offset)
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{
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struct io_fixed_file *file_slot;
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struct file *file;
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int ret;
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if (unlikely(!ctx->file_data))
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return -ENXIO;
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if (offset >= ctx->nr_user_files)
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return -EINVAL;
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ret = io_rsrc_node_switch_start(ctx);
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if (ret)
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return ret;
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offset = array_index_nospec(offset, ctx->nr_user_files);
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file_slot = io_fixed_file_slot(&ctx->file_table, offset);
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if (!file_slot->file_ptr)
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return -EBADF;
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file = (struct file *)(file_slot->file_ptr & FFS_MASK);
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ret = io_queue_rsrc_removal(ctx->file_data, offset, ctx->rsrc_node, file);
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if (ret)
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return ret;
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file_slot->file_ptr = 0;
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io_file_bitmap_clear(&ctx->file_table, offset);
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io_rsrc_node_switch(ctx, ctx->file_data);
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return 0;
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}
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int io_register_file_alloc_range(struct io_ring_ctx *ctx,
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struct io_uring_file_index_range __user *arg)
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{
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struct io_uring_file_index_range range;
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u32 end;
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if (copy_from_user(&range, arg, sizeof(range)))
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return -EFAULT;
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if (check_add_overflow(range.off, range.len, &end))
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return -EOVERFLOW;
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if (range.resv || end > ctx->nr_user_files)
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return -EINVAL;
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io_file_table_set_alloc_range(ctx, range.off, range.len);
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return 0;
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}
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