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Subject[PATCH v4 6/6] io_uring: add support for zone-append
Date
From: SelvaKumar S <selvakuma.s1@samsung.com>

Repurpose [cqe->res, cqe->flags] into cqe->res64 (signed) to report
64bit written-offset for zone-append. The appending-write which requires
reporting written-location (conveyed by IOCB_ZONE_APPEND flag) is
ensured not to be a short-write; this avoids the need to report
number-of-bytes-copied.
append-offset is returned by lower-layer to io-uring via ret2 of
ki_complete interface. Make changes to collect it and send to user-space
via cqe->res64.

Signed-off-by: SelvaKumar S <selvakuma.s1@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Javier Gonzalez <javier.gonz@samsung.com>
---
fs/io_uring.c | 49 ++++++++++++++++++++++++++++++++++++-------
include/uapi/linux/io_uring.h | 9 ++++++--
2 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7809ab2..6510cf5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -401,7 +401,14 @@ struct io_rw {
/* NOTE: kiocb has the file as the first member, so don't do it here */
struct kiocb kiocb;
u64 addr;
- u64 len;
+ union {
+ /*
+ * len is used only during submission.
+ * append_offset is used only during completion.
+ */
+ u64 len;
+ u64 append_offset;
+ };
};

struct io_connect {
@@ -541,6 +548,7 @@ enum {
REQ_F_NO_FILE_TABLE_BIT,
REQ_F_QUEUE_TIMEOUT_BIT,
REQ_F_WORK_INITIALIZED_BIT,
+ REQ_F_ZONE_APPEND_BIT,

/* not a real bit, just to check we're not overflowing the space */
__REQ_F_LAST_BIT,
@@ -598,6 +606,8 @@ enum {
REQ_F_QUEUE_TIMEOUT = BIT(REQ_F_QUEUE_TIMEOUT_BIT),
/* io_wq_work is initialized */
REQ_F_WORK_INITIALIZED = BIT(REQ_F_WORK_INITIALIZED_BIT),
+ /* to return zone append offset */
+ REQ_F_ZONE_APPEND = BIT(REQ_F_ZONE_APPEND_BIT),
};

struct async_poll {
@@ -1244,8 +1254,15 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)
req->flags &= ~REQ_F_OVERFLOW;
if (cqe) {
WRITE_ONCE(cqe->user_data, req->user_data);
- WRITE_ONCE(cqe->res, req->result);
- WRITE_ONCE(cqe->flags, req->cflags);
+ if (unlikely(req->flags & REQ_F_ZONE_APPEND)) {
+ if (likely(req->result > 0))
+ WRITE_ONCE(cqe->res64, req->rw.append_offset);
+ else
+ WRITE_ONCE(cqe->res64, req->result);
+ } else {
+ WRITE_ONCE(cqe->res, req->result);
+ WRITE_ONCE(cqe->flags, req->cflags);
+ }
} else {
WRITE_ONCE(ctx->rings->cq_overflow,
atomic_inc_return(&ctx->cached_cq_overflow));
@@ -1284,8 +1301,15 @@ static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags)
cqe = io_get_cqring(ctx);
if (likely(cqe)) {
WRITE_ONCE(cqe->user_data, req->user_data);
- WRITE_ONCE(cqe->res, res);
- WRITE_ONCE(cqe->flags, cflags);
+ if (unlikely(req->flags & REQ_F_ZONE_APPEND)) {
+ if (likely(res > 0))
+ WRITE_ONCE(cqe->res64, req->rw.append_offset);
+ else
+ WRITE_ONCE(cqe->res64, res);
+ } else {
+ WRITE_ONCE(cqe->res, res);
+ WRITE_ONCE(cqe->flags, cflags);
+ }
} else if (ctx->cq_overflow_flushed) {
WRITE_ONCE(ctx->rings->cq_overflow,
atomic_inc_return(&ctx->cached_cq_overflow));
@@ -1943,7 +1967,7 @@ static inline void req_set_fail_links(struct io_kiocb *req)
req->flags |= REQ_F_FAIL_LINK;
}

-static void io_complete_rw_common(struct kiocb *kiocb, long res)
+static void io_complete_rw_common(struct kiocb *kiocb, long res, long long res2)
{
struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);
int cflags = 0;
@@ -1955,6 +1979,9 @@ static void io_complete_rw_common(struct kiocb *kiocb, long res)
req_set_fail_links(req);
if (req->flags & REQ_F_BUFFER_SELECTED)
cflags = io_put_kbuf(req);
+ if (req->flags & REQ_F_ZONE_APPEND)
+ req->rw.append_offset = res2;
+
__io_cqring_add_event(req, res, cflags);
}

@@ -1962,7 +1989,7 @@ static void io_complete_rw(struct kiocb *kiocb, long res, long long res2)
{
struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw.kiocb);

- io_complete_rw_common(kiocb, res);
+ io_complete_rw_common(kiocb, res, res2);
io_put_req(req);
}

@@ -1976,8 +2003,11 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long long res2)
if (res != req->result)
req_set_fail_links(req);
req->result = res;
- if (res != -EAGAIN)
+ if (res != -EAGAIN) {
+ if (req->flags & REQ_F_ZONE_APPEND)
+ req->rw.append_offset = res2;
WRITE_ONCE(req->iopoll_completed, 1);
+ }
}

/*
@@ -2739,6 +2769,9 @@ static int io_write(struct io_kiocb *req, bool force_nonblock)
SB_FREEZE_WRITE);
}
kiocb->ki_flags |= IOCB_WRITE;
+ /* zone-append requires few extra steps during completion */
+ if (kiocb->ki_flags & IOCB_ZONE_APPEND)
+ req->flags |= REQ_F_ZONE_APPEND;

if (!force_nonblock)
current->signal->rlim[RLIMIT_FSIZE].rlim_cur = req->fsize;
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 92c2269..2580d93 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -156,8 +156,13 @@ enum {
*/
struct io_uring_cqe {
__u64 user_data; /* sqe->data submission passed back */
- __s32 res; /* result code for this event */
- __u32 flags;
+ union {
+ struct {
+ __s32 res; /* result code for this event */
+ __u32 flags;
+ };
+ __s64 res64; /* appending offset for zone append */
+ };
};

/*
--
2.7.4
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