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io_uring: let to set a range for file slot allocation

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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>
This commit is contained in:
Pavel Begunkov
2022-06-25 11:55:38 +01:00
committed by Jens Axboe
parent e6130eba8a
commit 6e73dffbb9
6 changed files with 61 additions and 7 deletions
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24
io_uring/filetable.c
View File

@@ -16,7 +16,7 @@
static int io_file_bitmap_get(struct io_ring_ctx *ctx)
{
struct io_file_table *table = &ctx->file_table;
unsigned long nr = ctx->nr_user_files;
unsigned long nr = ctx->file_alloc_end;
int ret;
do {
@@ -24,11 +24,10 @@ static int io_file_bitmap_get(struct io_ring_ctx *ctx)
if (ret != nr)
return ret;
if (!table->alloc_hint)
if (table->alloc_hint == ctx->file_alloc_start)
break;
nr = table->alloc_hint;
table->alloc_hint = 0;
table->alloc_hint = ctx->file_alloc_start;
} while (1);
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);
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;
}