Re: io_uring's openat doesn't work with large (2G+) files

[Jens Axboe <axboe@kernel.dk>]

On 4/8/20 7:51 AM, Dmitry Kadashev wrote:
> Hi,
> 
> io_uring's openat seems to produce FDs that are incompatible with
> large files (>2GB). If a file (smaller than 2GB) is opened using
> io_uring's openat then writes -- both using io_uring and just sync
> pwrite() -- past that threshold fail with EFBIG. If such a file is
> opened with sync openat, then both io_uring's writes and sync writes
> succeed. And if the file is larger than 2GB then io_uring's openat
> fails right away, while the sync one works.
> 
> Kernel versions: 5.6.0-rc2, 5.6.0.
> 
> A couple of reproducers attached, one demos successful open with
> failed writes afterwards, and another failing open (in comparison with
> sync  calls).
> 
> The output of the former one for example:
> 
> *** sync openat
> openat succeeded
> sync write at offset 0
> write succeeded
> sync write at offset 4294967296
> write succeeded
> 
> *** sync openat
> openat succeeded
> io_uring write at offset 0
> write succeeded
> io_uring write at offset 4294967296
> write succeeded
> 
> *** io_uring openat
> openat succeeded
> sync write at offset 0
> write succeeded
> sync write at offset 4294967296
> write failed: File too large
> 
> *** io_uring openat
> openat succeeded
> io_uring write at offset 0
> write succeeded
> io_uring write at offset 4294967296
> write failed: File too large

Can you try with this one? Seems like only openat2 gets it set,
not openat...


diff --git a/fs/io_uring.c b/fs/io_uring.c
index 79bd22289d73..63eb7efe10f2 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2957,6 +2957,8 @@ static int io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	req->open.how.mode = READ_ONCE(sqe->len);
 	fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	req->open.how.flags = READ_ONCE(sqe->open_flags);
+	if (force_o_largefile())
+		req->open.how.flags |= O_LARGEFILE;
 
 	req->open.filename = getname(fname);
 	if (IS_ERR(req->open.filename)) {

-- 
Jens Axboe