io_uring: flag the fact that linked file assignment is sane

Give applications a way to tell if the kernel supports sane linked files,
as in files being assigned at the right time to be able to reliably
do <open file direct into slot X><read file from slot X> while using
IOSQE_IO_LINK to order them.

Not really a bug fix, but flag it as such so that it gets pulled in with
backports of the deferred file assignment.

Fixes: 6bf9c47a3989 ("io_uring: defer file assignment")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 659f8ec..f060ad0 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -11178,7 +11178,8 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
                        IORING_FEAT_CUR_PERSONALITY | IORING_FEAT_FAST_POLL |
                        IORING_FEAT_POLL_32BITS | IORING_FEAT_SQPOLL_NONFIXED |
                        IORING_FEAT_EXT_ARG | IORING_FEAT_NATIVE_WORKERS |
-                       IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP;
+                       IORING_FEAT_RSRC_TAGS | IORING_FEAT_CQE_SKIP |
+                       IORING_FEAT_LINKED_FILE;
 
        if (copy_to_user(params, p, sizeof(*p))) {
                ret = -EFAULT;

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 784adc6..1845cf7 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -296,6 +296,7 @@ struct io_uring_params {
 #define IORING_FEAT_NATIVE_WORKERS     (1U << 9)
 #define IORING_FEAT_RSRC_TAGS          (1U << 10)
 #define IORING_FEAT_CQE_SKIP           (1U << 11)
+#define IORING_FEAT_LINKED_FILE                (1U << 12)
 
 /*
  * io_uring_register(2) opcodes and arguments