We've got two issues with the non-regular file handling for non-blocking
IO:
1) We don't want to re-do a short read in full for a non-regular file,
as we can't just read the data again.
2) For non-regular files that don't support non-blocking IO attempts,
we need to punt to async context even if the file is opened as
non-blocking. Otherwise the caller always gets -EAGAIN.
Add two new request flags to handle these cases. One is just a cache
of the inode S_ISREG() status, the other tells io_uring that we always
need to punt this request to async context, even if REQ_F_NOWAIT is set.
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Hrvoje Zeba <zeba.hrvoje@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
fs/io_uring.c | 55 +++++++++++++++++++++++++++++++++++----------------
1 file changed, 38 insertions(+), 17 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d2cb277da2f4..a4ee5436cb61 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -322,6 +322,8 @@ struct io_kiocb {
#define REQ_F_FAIL_LINK 256 /* fail rest of links */
#define REQ_F_SHADOW_DRAIN 512 /* link-drain shadow req */
#define REQ_F_TIMEOUT 1024 /* timeout request */
+#define REQ_F_ISREG 2048 /* regular file */
+#define REQ_F_MUST_PUNT 4096 /* must be punted even for NONBLOCK */
u64 user_data;
u32 result;
u32 sequence;
@@ -914,26 +916,26 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events,
return ret;
}
-static void kiocb_end_write(struct kiocb *kiocb)
+static void kiocb_end_write(struct io_kiocb *req)
{
- if (kiocb->ki_flags & IOCB_WRITE) {
- struct inode *inode = file_inode(kiocb->ki_filp);
+ /*
+ * Tell lockdep we inherited freeze protection from submission
+ * thread.
+ */
+ if (req->flags & REQ_F_ISREG) {
+ struct inode *inode = file_inode(req->file);
- /*
- * Tell lockdep we inherited freeze protection from submission
- * thread.
- */
- if (S_ISREG(inode->i_mode))
- __sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
- file_end_write(kiocb->ki_filp);
+ __sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
}
+ file_end_write(req->file);
}
static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
{
struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw);
- kiocb_end_write(kiocb);
+ if (kiocb->ki_flags & IOCB_WRITE)
+ kiocb_end_write(req);
if ((req->flags & REQ_F_LINK) && res != req->result)
req->flags |= REQ_F_FAIL_LINK;
@@ -945,7 +947,8 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2)
{
struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw);
- kiocb_end_write(kiocb);
+ if (kiocb->ki_flags & IOCB_WRITE)
+ kiocb_end_write(req);
if ((req->flags & REQ_F_LINK) && res != req->result)
req->flags |= REQ_F_FAIL_LINK;
@@ -1059,8 +1062,17 @@ static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s,
if (!req->file)
return -EBADF;
- if (force_nonblock && !io_file_supports_async(req->file))
+ if (S_ISREG(file_inode(req->file)->i_mode))
+ req->flags |= REQ_F_ISREG;
+
+ /*
+ * If the file doesn't support async, mark it as REQ_F_MUST_PUNT so
+ * we know to async punt it even if it was opened O_NONBLOCK
+ */
+ if (force_nonblock && !io_file_supports_async(req->file)) {
force_nonblock = false;
+ req->flags |= REQ_F_MUST_PUNT;
+ }
kiocb->ki_pos = READ_ONCE(sqe->off);
kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
@@ -1081,7 +1093,8 @@ static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s,
return ret;
/* don't allow async punt if RWF_NOWAIT was requested */
- if (kiocb->ki_flags & IOCB_NOWAIT)
+ if ((kiocb->ki_flags & IOCB_NOWAIT) ||
+ (req->file->f_flags & O_NONBLOCK))
req->flags |= REQ_F_NOWAIT;
if (force_nonblock)
@@ -1382,7 +1395,9 @@ static int io_read(struct io_kiocb *req, const struct sqe_submit *s,
* need async punt anyway, so it's more efficient to do it
* here.
*/
- if (force_nonblock && ret2 > 0 && ret2 < read_size)
+ if (force_nonblock && !(req->flags & REQ_F_NOWAIT) &&
+ (req->flags & REQ_F_ISREG) &&
+ ret2 > 0 && ret2 < read_size)
ret2 = -EAGAIN;
/* Catch -EAGAIN return for forced non-blocking submission */
if (!force_nonblock || ret2 != -EAGAIN) {
@@ -1447,7 +1462,7 @@ static int io_write(struct io_kiocb *req, const struct sqe_submit *s,
* released so that it doesn't complain about the held lock when
* we return to userspace.
*/
- if (S_ISREG(file_inode(file)->i_mode)) {
+ if (req->flags & REQ_F_ISREG) {
__sb_start_write(file_inode(file)->i_sb,
SB_FREEZE_WRITE, true);
__sb_writers_release(file_inode(file)->i_sb,
@@ -2282,7 +2297,13 @@ static int __io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
int ret;
ret = __io_submit_sqe(ctx, req, s, force_nonblock);
- if (ret == -EAGAIN && !(req->flags & REQ_F_NOWAIT)) {
+
+ /*
+ * We async punt it if the file wasn't marked NOWAIT, or if the file
+ * doesn't support non-blocking read/write attempts
+ */
+ if (ret == -EAGAIN && (!(req->flags & REQ_F_NOWAIT) ||
+ (req->flags & REQ_F_MUST_PUNT))) {
struct io_uring_sqe *sqe_copy;
sqe_copy = kmemdup(s->sqe, sizeof(*sqe_copy), GFP_KERNEL);
--
2.17.1
--
Jens Axboe
