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Message-Id: <fe6429fbbf964463049496a2d24a649d728561a0.1629559905.git.asml.silence@gmail.com>
Date: Sat, 21 Aug 2021 16:52:38 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
Josh Triplett <josh@...htriplett.org>
Cc: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org, Stefan Metzmacher <metze@...ba.org>
Subject: [PATCH v3 2/4] io_uring: openat directly into fixed fd table
Instead of opening a file into a process's file table as usual and then
registering the fd within io_uring, some users may want to skip the
first step and place it directly into io_uring's fixed file table.
This patch adds such a capability for IORING_OP_OPENAT and
IORING_OP_OPENAT2.
The behaviour is controlled by setting sqe->file_index, where 0 implies
the old behaviour. If non-zero value is specified, then it will behave
as described and place the file into a fixed file slot
sqe->file_index - 1. A file table should be already created, the slot
should be valid and empty, otherwise the operation will fail.
Keep the error codes consistent with IORING_OP_FILES_UPDATE, ENXIO and
EINVAL on inappropriate fixed tables, and return EBADF on collision with
already registered file.
Note: we can't use IOSQE_FIXED_FILE to switch between modes, because
accept takes a file, and it already uses the flag with a different
meaning.
Suggested-by: Josh Triplett <josh@...htriplett.org>
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
fs/io_uring.c | 82 +++++++++++++++++++++++++++++++----
include/uapi/linux/io_uring.h | 5 ++-
2 files changed, 78 insertions(+), 9 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 0fb75aa72b69..b8ef5ac1f90d 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1063,6 +1063,9 @@ static void io_req_task_queue(struct io_kiocb *req);
static void io_submit_flush_completions(struct io_ring_ctx *ctx);
static int io_req_prep_async(struct io_kiocb *req);
+static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
+ unsigned int issue_flags);
+
static struct kmem_cache *req_cachep;
static const struct file_operations io_uring_fops;
@@ -3815,11 +3818,12 @@ static int io_fallocate(struct io_kiocb *req, unsigned int issue_flags)
static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
const char __user *fname;
+ unsigned index;
int ret;
if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
return -EINVAL;
- if (unlikely(sqe->ioprio || sqe->buf_index || sqe->splice_fd_in))
+ if (unlikely(sqe->ioprio || sqe->buf_index))
return -EINVAL;
if (unlikely(req->flags & REQ_F_FIXED_FILE))
return -EBADF;
@@ -3836,6 +3840,16 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
req->open.filename = NULL;
return ret;
}
+
+ index = READ_ONCE(sqe->file_index);
+ req->buf_index = index;
+ if (index) {
+ if (req->open.how.flags & O_CLOEXEC)
+ return -EINVAL;
+ if (req->buf_index != index)
+ return -EINVAL;
+ }
+
req->open.nofile = rlimit(RLIMIT_NOFILE);
req->flags |= REQ_F_NEED_CLEANUP;
return 0;
@@ -3873,8 +3887,8 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
{
struct open_flags op;
struct file *file;
- bool nonblock_set;
- bool resolve_nonblock;
+ bool resolve_nonblock, nonblock_set;
+ bool fixed = !!req->buf_index;
int ret;
ret = build_open_flags(&req->open.how, &op);
@@ -3893,9 +3907,11 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
op.open_flag |= O_NONBLOCK;
}
- ret = __get_unused_fd_flags(req->open.how.flags, req->open.nofile);
- if (ret < 0)
- goto err;
+ if (!fixed) {
+ ret = __get_unused_fd_flags(req->open.how.flags, req->open.nofile);
+ if (ret < 0)
+ goto err;
+ }
file = do_filp_open(req->open.dfd, req->open.filename, &op);
if (IS_ERR(file)) {
@@ -3904,7 +3920,8 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
* marginal gain for something that is now known to be a slower
* path. So just put it, and we'll get a new one when we retry.
*/
- put_unused_fd(ret);
+ if (!fixed)
+ put_unused_fd(ret);
ret = PTR_ERR(file);
/* only retry if RESOLVE_CACHED wasn't already set by application */
@@ -3917,7 +3934,11 @@ static int io_openat2(struct io_kiocb *req, unsigned int issue_flags)
if ((issue_flags & IO_URING_F_NONBLOCK) && !nonblock_set)
file->f_flags &= ~O_NONBLOCK;
fsnotify_open(file);
- fd_install(ret, file);
+
+ if (!fixed)
+ fd_install(ret, file);
+ else
+ ret = io_install_fixed_file(req, file, issue_flags);
err:
putname(req->open.filename);
req->flags &= ~REQ_F_NEED_CLEANUP;
@@ -7846,6 +7867,50 @@ static int io_sqe_file_register(struct io_ring_ctx *ctx, struct file *file,
#endif
}
+static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
+ unsigned int issue_flags)
+{
+ struct io_ring_ctx *ctx = req->ctx;
+ int i = req->buf_index - 1;
+ bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
+ struct io_fixed_file *file_slot;
+ int ret = -EBADF;
+
+ if (WARN_ON_ONCE(req->buf_index == 0))
+ goto err;
+
+ io_ring_submit_lock(ctx, !force_nonblock);
+ if (file->f_op == &io_uring_fops)
+ goto err;
+ ret = -ENXIO;
+ if (!ctx->file_data)
+ goto err;
+ ret = -EINVAL;
+ if (i >= ctx->nr_user_files)
+ goto err;
+
+ i = array_index_nospec(i, ctx->nr_user_files);
+ file_slot = io_fixed_file_slot(&ctx->file_table, i);
+ ret = -EBADF;
+ if (file_slot->file_ptr)
+ goto err;
+
+ *io_get_tag_slot(ctx->file_data, i) = 0;
+ io_fixed_file_set(file_slot, file);
+ ret = io_sqe_file_register(ctx, file, i);
+ if (ret) {
+ file_slot->file_ptr = 0;
+ goto err;
+ }
+
+ ret = 0;
+err:
+ io_ring_submit_unlock(ctx, !force_nonblock);
+ if (ret)
+ fput(file);
+ return ret;
+}
+
static int io_queue_rsrc_removal(struct io_rsrc_data *data, unsigned idx,
struct io_rsrc_node *node, void *rsrc)
{
@@ -10311,6 +10376,7 @@ static int __init io_uring_init(void)
BUILD_BUG_SQE_ELEM(40, __u16, buf_group);
BUILD_BUG_SQE_ELEM(42, __u16, personality);
BUILD_BUG_SQE_ELEM(44, __s32, splice_fd_in);
+ BUILD_BUG_SQE_ELEM(44, __u32, file_index);
BUILD_BUG_ON(sizeof(struct io_uring_files_update) !=
sizeof(struct io_uring_rsrc_update));
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 79126d5cd289..45a4f2373694 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -55,7 +55,10 @@ struct io_uring_sqe {
} __attribute__((packed));
/* personality to use, if used */
__u16 personality;
- __s32 splice_fd_in;
+ union {
+ __s32 splice_fd_in;
+ __u32 file_index;
+ };
__u64 __pad2[2];
};
--
2.32.0
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