The patch below does not apply to the 5.3-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 491381ce07ca57f68c49c79a8a43da5b60749e32 Mon Sep 17 00:00:00 2001
From: Jens Axboe axboe@kernel.dk Date: Thu, 17 Oct 2019 09:20:46 -0600 Subject: [PATCH] io_uring: fix up O_NONBLOCK handling for sockets
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@vger.kernel.org Reported-by: Hrvoje Zeba zeba.hrvoje@gmail.com Tested-by: Hrvoje Zeba zeba.hrvoje@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk
diff --git a/fs/io_uring.c b/fs/io_uring.c index d2cb277da2f4..b7d4085d6ffd 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)) - force_nonblock = false; + 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)) { + req->flags |= REQ_F_MUST_PUNT; + return -EAGAIN; + }
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);