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From: "Oliver Giles" <ohw.giles@gmail.com>
To: "Robert Karszniewicz" <r.karszniewicz@phytec.de>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Linus Torvalds" <torvalds@linux-foundation.org>
Cc: "Christoph Hellwig" <hch@lst.de>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Jiri Slaby" <jirislaby@kernel.org>
Subject: Re: Splicing to/from a tty
Date: Wed, 20 Jan 2021 11:09:18 +1300	[thread overview]
Message-ID: <C8NH7QWZG2CR.3RT2AKK0ESMYE@oguc> (raw)
In-Reply-To: <9d3baff9-5d4a-4308-9556-8dd037c2fe4b@phytec.de>

On Wed Jan 20, 2021 at 5:56 AM NZDT, Robert Karszniewicz wrote:
>
> I have bisected this issue down to this commit:
> 4d03e3cc5982 ("fs: don't allow kernel reads and writes without iter
> ops")
>
> Another case I've also noticed is writing to a serial connection:
> kernel write not supported for file /ttymxc0 (pid: 252 comm: cat)
>

Tangentially, I hit the same thing when hacking on this. Here's a diff
making the implementation match the comment:

--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -541,7 +541,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
         * Also fail if ->write_iter and ->write are both wired up as that
         * implies very convoluted semantics.
         */
-       if (unlikely(!file->f_op->write_iter || file->f_op->write))
+       if (unlikely(file->f_op->write_iter && file->f_op->write))
                return warn_unsupported(file, "write");
 
        init_sync_kiocb(&kiocb, file);


  parent reply	other threads:[~2021-01-19 22:13 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-16  7:35 Splicing to/from a tty Oliver Giles
2021-01-16 16:46 ` Johannes Berg
2021-01-17  6:12   ` Oliver Giles
2021-01-18  8:53   ` Christoph Hellwig
2021-01-18  8:58     ` Johannes Berg
2021-01-18 19:26       ` Linus Torvalds
2021-01-18 19:45         ` Al Viro
2021-01-18 19:49           ` Linus Torvalds
2021-01-18 19:56             ` Al Viro
2021-01-24 19:11           ` Linus Torvalds
2021-01-25  9:16             ` [PATCH] fs/pipe: allow sendfile() to pipe again Johannes Berg
2021-01-25 10:16               ` Christoph Hellwig
2021-01-25 20:34               ` Linus Torvalds
2021-01-26  6:07             ` Splicing to/from a tty Al Viro
2021-01-26  6:08               ` [PATCH 1/3] do_splice_to(): move the logics for limiting the read length in Al Viro
2021-01-26  6:09               ` [PATCH 2/3] take the guts of file-to-pipe splice into a helper function Al Viro
2021-01-26  6:09               ` [PATCH 3/3] teach sendfile(2) to handle send-to-pipe directly Al Viro
2021-01-26 18:57                 ` Linus Torvalds
2021-01-26 19:33                   ` Al Viro
2021-01-26 18:49               ` Splicing to/from a tty Linus Torvalds
2021-01-26 19:42                 ` Al Viro
2021-01-18 19:34     ` Al Viro
2021-01-18 19:46       ` Linus Torvalds
2021-01-18 19:54         ` Al Viro
2021-01-20 16:26           ` Al Viro
2021-01-20 19:11             ` Al Viro
2021-01-20 19:27               ` Linus Torvalds
2021-01-20 22:25                 ` David Laight
2021-01-20 23:02                   ` Al Viro
2021-01-20 23:14                 ` Al Viro
2021-01-20 23:40                   ` Linus Torvalds
2021-01-21  0:38                     ` Al Viro
2021-01-21  1:04                       ` Linus Torvalds
2021-01-21  1:45                         ` Al Viro
2021-01-21  3:38                           ` Linus Torvalds
2021-01-21  6:05                             ` Willy Tarreau
2021-01-21  8:04                               ` Johannes Berg
2021-01-21 10:08                         ` David Laight
2021-01-18  8:16 ` Christoph Hellwig
2021-01-18 19:36   ` Linus Torvalds
2021-01-18 20:24     ` Linus Torvalds
2021-01-18 21:35       ` Linus Torvalds
2021-01-18 21:54         ` Linus Torvalds
2021-01-18 22:03           ` Linus Torvalds
2021-01-18 22:20             ` Linus Torvalds
2021-01-19  1:38               ` Linus Torvalds
2021-01-19 11:53                 ` Greg Kroah-Hartman
2021-01-19 16:56                   ` Robert Karszniewicz
2021-01-19 17:10                     ` Robert Karszniewicz
2021-01-19 22:09                     ` Oliver Giles [this message]
2021-01-19 17:25                   ` Linus Torvalds
2021-01-19 20:24                   ` Linus Torvalds
2021-01-19 20:38                     ` Christoph Hellwig
2021-01-20  1:25                     ` Oliver Giles
2021-01-20  4:44                       ` Linus Torvalds
2021-01-20  8:15                         ` Oliver Giles
2021-01-21  1:18                         ` tty splice branch (was "Re: Splicing to/from a tty") Linus Torvalds
2021-01-21  8:44                           ` Greg Kroah-Hartman
2021-01-21  8:50                           ` Jiri Slaby
2021-01-21  8:58                             ` Jiri Slaby
2021-01-21 17:52                               ` Linus Torvalds
2021-01-21  8:58                             ` Greg Kroah-Hartman
2021-01-21 17:03                         ` Splicing to/from a tty Robert Karszniewicz
2021-01-21 18:43                           ` Linus Torvalds
2021-01-19 11:52         ` Greg Kroah-Hartman

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