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authorJens Axboe <axboe@kernel.dk>2019-12-25 16:33:42 -0700
committerJens Axboe <axboe@kernel.dk>2020-01-20 17:03:59 -0700
commitba04291eb66ed895f194ae5abd3748d72bf8aaea (patch)
tree398b8455348b4b2a2171554f01447c74ffb9f28e
parent3a6820f2bb8a079975109c25a5d1f29f46bce5d2 (diff)
io_uring: allow use of offset == -1 to mean file position
This behaves like preadv2/pwritev2 with offset == -1, it'll use (and update) the current file position. This obviously comes with the caveat that if the application has multiple read/writes in flight, then the end result will not be as expected. This is similar to threads sharing a file descriptor and doing IO using the current file position. Since this feature isn't easily detectable by doing a read or write, add a feature flags, IORING_FEAT_RW_CUR_POS, to allow applications to detect presence of this feature. Reported-by: 李通洲 <carter.li@eoitek.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--fs/io_uring.c11
-rw-r--r--include/uapi/linux/io_uring.h1
2 files changed, 11 insertions, 1 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 407ba3388e14..5286620e4e46 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -495,6 +495,7 @@ struct io_kiocb {
#define REQ_F_COMP_LOCKED 32768 /* completion under lock */
#define REQ_F_HARDLINK 65536 /* doesn't sever on completion < 0 */
#define REQ_F_FORCE_ASYNC 131072 /* IOSQE_ASYNC */
+#define REQ_F_CUR_POS 262144 /* read/write uses file position */
u64 user_data;
u32 result;
u32 sequence;
@@ -1711,6 +1712,10 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
req->flags |= REQ_F_ISREG;
kiocb->ki_pos = READ_ONCE(sqe->off);
+ if (kiocb->ki_pos == -1 && !(req->file->f_mode & FMODE_STREAM)) {
+ req->flags |= REQ_F_CUR_POS;
+ kiocb->ki_pos = req->file->f_pos;
+ }
kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp));
@@ -1782,6 +1787,10 @@ static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret)
static void kiocb_done(struct kiocb *kiocb, ssize_t ret, struct io_kiocb **nxt,
bool in_async)
{
+ struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
+
+ if (req->flags & REQ_F_CUR_POS)
+ req->file->f_pos = kiocb->ki_pos;
if (in_async && ret >= 0 && kiocb->ki_complete == io_complete_rw)
*nxt = __io_complete_rw(kiocb, ret);
else
@@ -6154,7 +6163,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
goto err;
p->features = IORING_FEAT_SINGLE_MMAP | IORING_FEAT_NODROP |
- IORING_FEAT_SUBMIT_STABLE;
+ IORING_FEAT_SUBMIT_STABLE | IORING_FEAT_RW_CUR_POS;
trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags);
return ret;
err:
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 7fdf994f3313..1f96136eb6ee 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -174,6 +174,7 @@ struct io_uring_params {
#define IORING_FEAT_SINGLE_MMAP (1U << 0)
#define IORING_FEAT_NODROP (1U << 1)
#define IORING_FEAT_SUBMIT_STABLE (1U << 2)
+#define IORING_FEAT_RW_CUR_POS (1U << 3)
/*
* io_uring_register(2) opcodes and arguments