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Subject[PATCH v3 2/2] io_uring: add support for IORING_OP_GETDENTS
IORING_OP_GETDENTS behaves much like getdents64(2) and takes the same
arguments, but with a small twist: it takes an additional offset
argument, and reading from the specified directory starts at the given
offset.

For the first IORING_OP_GETDENTS call on a directory, the offset
parameter can be set to zero, and for subsequent calls, it can be
set to the ->d_off field of the last struct linux_dirent64 returned
by the previous IORING_OP_GETDENTS call.

Internally, if necessary, IORING_OP_GETDENTS will vfs_llseek() to
the right directory position before calling vfs_getdents().

IORING_OP_GETDENTS may or may not update the specified directory's
file offset, and the file offset should not be relied upon having
any particular value during or after an IORING_OP_GETDENTS call.

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
---
fs/io_uring.c | 73 +++++++++++++++++++++++++++++++++++
include/uapi/linux/io_uring.h | 1 +
2 files changed, 74 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 056bd4c90ade..6853bf48369a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -635,6 +635,13 @@ struct io_mkdir {
struct filename *filename;
};

+struct io_getdents {
+ struct file *file;
+ struct linux_dirent64 __user *dirent;
+ unsigned int count;
+ loff_t pos;
+};
+
struct io_completion {
struct file *file;
struct list_head list;
@@ -772,6 +779,7 @@ struct io_kiocb {
struct io_rename rename;
struct io_unlink unlink;
struct io_mkdir mkdir;
+ struct io_getdents getdents;
/* use only after cleaning per-op data, see io_clean_op() */
struct io_completion compl;
};
@@ -1030,6 +1038,11 @@ static const struct io_op_def io_op_defs[] = {
.work_flags = IO_WQ_WORK_MM | IO_WQ_WORK_FILES |
IO_WQ_WORK_FS | IO_WQ_WORK_BLKCG,
},
+ [IORING_OP_GETDENTS] = {
+ .needs_file = 1,
+ .work_flags = IO_WQ_WORK_MM | IO_WQ_WORK_FILES |
+ IO_WQ_WORK_FS | IO_WQ_WORK_BLKCG,
+ },
};

static void io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
@@ -4677,6 +4690,61 @@ static int io_sync_file_range(struct io_kiocb *req, unsigned int issue_flags)
return 0;
}

+static int io_getdents_prep(struct io_kiocb *req,
+ const struct io_uring_sqe *sqe)
+{
+ struct io_getdents *getdents = &req->getdents;
+
+ if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
+ return -EINVAL;
+ if (sqe->ioprio || sqe->rw_flags || sqe->buf_index)
+ return -EINVAL;
+
+ getdents->pos = READ_ONCE(sqe->off);
+ getdents->dirent = u64_to_user_ptr(READ_ONCE(sqe->addr));
+ getdents->count = READ_ONCE(sqe->len);
+ return 0;
+}
+
+static int io_getdents(struct io_kiocb *req, unsigned int issue_flags)
+{
+ struct io_getdents *getdents = &req->getdents;
+ bool pos_unlock = false;
+ int ret = 0;
+
+ /* getdents always requires a blocking context */
+ if (issue_flags & IO_URING_F_NONBLOCK)
+ return -EAGAIN;
+
+ /* for vfs_llseek and to serialize ->iterate_shared() on this file */
+ if (file_count(req->file) > 1) {
+ pos_unlock = true;
+ mutex_lock(&req->file->f_pos_lock);
+ }
+
+ if (req->file->f_pos != getdents->pos) {
+ loff_t res = vfs_llseek(req->file, getdents->pos, SEEK_SET);
+ if (res < 0)
+ ret = res;
+ }
+
+ if (ret == 0) {
+ ret = vfs_getdents(req->file, getdents->dirent,
+ getdents->count);
+ }
+
+ if (pos_unlock)
+ mutex_unlock(&req->file->f_pos_lock);
+
+ if (ret < 0) {
+ if (ret == -ERESTARTSYS)
+ ret = -EINTR;
+ req_set_fail_links(req);
+ }
+ io_req_complete(req, ret);
+ return 0;
+}
+
#if defined(CONFIG_NET)
static int io_setup_async_msg(struct io_kiocb *req,
struct io_async_msghdr *kmsg)
@@ -6184,6 +6252,8 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
return io_unlinkat_prep(req, sqe);
case IORING_OP_MKDIRAT:
return io_mkdirat_prep(req, sqe);
+ case IORING_OP_GETDENTS:
+ return io_getdents_prep(req, sqe);
}

printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
@@ -6428,6 +6498,9 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
case IORING_OP_MKDIRAT:
ret = io_mkdirat(req, issue_flags);
break;
+ case IORING_OP_GETDENTS:
+ ret = io_getdents(req, issue_flags);
+ break;
default:
ret = -EINVAL;
break;
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 890edd850a9e..fe097b1fa332 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -138,6 +138,7 @@ enum {
IORING_OP_RENAMEAT,
IORING_OP_UNLINKAT,
IORING_OP_MKDIRAT,
+ IORING_OP_GETDENTS,

/* this goes last, obviously */
IORING_OP_LAST,
--
2.29.2
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