io_uring: track fixed files with a bitmap

In preparation for adding a basic allocator for direct descriptors,
add helpers that set/clear whether a file slot is used.

Reviewed-by: Hao Xu <howeyxu@tencent.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 22699cb359e94ebcc9f1b79054afc453745bde54..f8a685cc036354e7fc82fbb56a39821ae526d242 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -257,6 +257,7 @@ struct io_rsrc_put {
 
 struct io_file_table {
        struct io_fixed_file *files;
+       unsigned long *bitmap;
 };
 
 struct io_rsrc_node {
@@ -7572,6 +7573,7 @@ static inline struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
        /* mask in overlapping REQ_F and FFS bits */
        req->flags |= (file_ptr << REQ_F_SUPPORT_NOWAIT_BIT);
        io_req_set_rsrc_node(req, ctx, 0);
+       WARN_ON_ONCE(file && !test_bit(fd, ctx->file_table.bitmap));
 out:
        io_ring_submit_unlock(ctx, issue_flags);
        return file;
@@ -8638,13 +8640,35 @@ static bool io_alloc_file_tables(struct io_file_table *table, unsigned nr_files)
 {
        table->files = kvcalloc(nr_files, sizeof(table->files[0]),
                                GFP_KERNEL_ACCOUNT);
-       return !!table->files;
+       if (unlikely(!table->files))
+               return false;
+
+       table->bitmap = bitmap_zalloc(nr_files, GFP_KERNEL_ACCOUNT);
+       if (unlikely(!table->bitmap)) {
+               kvfree(table->files);
+               return false;
+       }
+
+       return true;
 }
 
 static void io_free_file_tables(struct io_file_table *table)
 {
        kvfree(table->files);
+       bitmap_free(table->bitmap);
        table->files = NULL;
+       table->bitmap = NULL;
+}
+
+static inline void io_file_bitmap_set(struct io_file_table *table, int bit)
+{
+       WARN_ON_ONCE(test_bit(bit, table->bitmap));
+       __set_bit(bit, table->bitmap);
+}
+
+static inline void io_file_bitmap_clear(struct io_file_table *table, int bit)
+{
+       __clear_bit(bit, table->bitmap);
 }
 
 static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
@@ -8659,6 +8683,7 @@ static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
                        continue;
                if (io_fixed_file_slot(&ctx->file_table, i)->file_ptr & FFS_SCM)
                        continue;
+               io_file_bitmap_clear(&ctx->file_table, i);
                fput(file);
        }
 #endif
@@ -9062,6 +9087,7 @@ static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
                }
                file_slot = io_fixed_file_slot(&ctx->file_table, i);
                io_fixed_file_set(file_slot, file);
+               io_file_bitmap_set(&ctx->file_table, i);
        }
 
        io_rsrc_node_switch(ctx, NULL);
@@ -9122,6 +9148,7 @@ static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
                if (ret)
                        goto err;
                file_slot->file_ptr = 0;
+               io_file_bitmap_clear(&ctx->file_table, slot_index);
                needs_switch = true;
        }
 
@@ -9129,6 +9156,7 @@ static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
        if (!ret) {
                *io_get_tag_slot(ctx->file_data, slot_index) = 0;
                io_fixed_file_set(file_slot, file);
+               io_file_bitmap_set(&ctx->file_table, slot_index);
        }
 err:
        if (needs_switch)
@@ -9170,6 +9198,7 @@ static int io_close_fixed(struct io_kiocb *req, unsigned int issue_flags)
                goto out;
 
        file_slot->file_ptr = 0;
+       io_file_bitmap_clear(&ctx->file_table, offset);
        io_rsrc_node_switch(ctx, ctx->file_data);
        ret = 0;
 out:
@@ -9219,6 +9248,7 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                        if (err)
                                break;
                        file_slot->file_ptr = 0;
+                       io_file_bitmap_clear(&ctx->file_table, i);
                        needs_switch = true;
                }
                if (fd != -1) {
@@ -9247,6 +9277,7 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
                        }
                        *io_get_tag_slot(data, i) = tag;
                        io_fixed_file_set(file_slot, file);
+                       io_file_bitmap_set(&ctx->file_table, i);
                }
        }