From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>, Miklos Szeredi <mszeredi@suse.cz>,
linux-aio@kvack.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 3/5] fs: remove ki_nbytes
Date: Mon, 2 Feb 2015 15:26:17 +0100 [thread overview]
Message-ID: <20150202142617.GC17447@lst.de> (raw)
In-Reply-To: <20150202081431.GX29656@ZenIV.linux.org.uk>
On Mon, Feb 02, 2015 at 08:14:31AM +0000, Al Viro wrote:
> 13) two odd drivers/usb/gadget instances. I have conversion for f_fs.c,
> but legacy/inode.c (ep_read() et.al.) is trickier. The problem in there
> is that writev() on a single-element vector is *not* equivalent to plain
> write(). The former treats the wrong-direction endpoint as EINVAL; the
> latter does
> if (usb_endpoint_xfer_isoc(&data->desc)) {
> mutex_unlock(&data->lock);
> return -EINVAL;
> }
> DBG (data->dev, "%s halt\n", data->name);
> spin_lock_irq (&data->dev->lock);
> if (likely (data->ep != NULL))
> usb_ep_set_halt (data->ep);
> spin_unlock_irq (&data->dev->lock);
> mutex_unlock(&data->lock);
> return -EBADMSG;
> instead. IOW, for isochronous endpoints behaviour is the same, but the
> rest behaves differently. If not for that, that sucker would convert
> to (3) easily;
I would bet the behavior difference is a bug, might be worth to Cc the
usb folks on this issue. I bet we'd want the more complex behavior
for both variants.
> 14) ipathfs and qibfs: seriously different semantics for write and writev/AIO
> write. As in "different set of commands recognized"; AIO write plays like
> writev, whether it's vectored or not (and it's always synchronous).
> I've no idea who had come up with that... highly innovative API or why
> hadn't they simply added two files (it's all on their virtual filesystem,
> so they had full control of layout) rather that multiplexing two different
> command sets in such a fashion.
>
> 15) /dev/snd/pcmC*D*[cp]. Again, different semantics for write and writev,
> with the latter wanting nr_seqs equal to the number of channels. AIO
> non-vectored write fails unless there's only one channel. Not sure how
> ALSA userland uses that thing; AIO side is always synchronous, so it might
> be simply never used. FWIW, I'm not sure that write() on a single-channel
> one is equivalent to 1-element writev() - silencing-related logics seem to
> differ.
For these weirdos we can pass down a flag in the kiocb about the source
of the I/O. We'll need that flags field for non-blocking buffered reads
and per-I/O O_SYNC anyway, and it will be very useful for fixing the
races around changing the O_DIRECT flag at run time.
next prev parent reply other threads:[~2015-02-02 14:26 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-27 17:55 [RFC] split struct kiocb Christoph Hellwig
2015-01-27 17:55 ` [PATCH 1/5] fs: don't allow to complete sync iocbs through aio_complete Christoph Hellwig
2015-01-28 15:30 ` Miklos Szeredi
2015-01-28 16:57 ` Christoph Hellwig
2015-01-31 3:01 ` Maxim Patlasov
2015-01-27 17:55 ` [PATCH 2/5] fs: saner aio_complete prototype Christoph Hellwig
2015-01-31 10:04 ` Al Viro
2015-01-27 17:55 ` [PATCH 3/5] fs: remove ki_nbytes Christoph Hellwig
2015-01-31 6:08 ` Al Viro
2015-02-02 8:07 ` Christoph Hellwig
2015-02-02 8:11 ` Al Viro
2015-02-02 8:14 ` Al Viro
2015-02-02 14:26 ` Christoph Hellwig [this message]
2015-02-04 8:34 ` Al Viro
2015-02-04 18:17 ` Alan Stern
2015-02-04 19:06 ` Al Viro
2015-02-04 20:30 ` Alan Stern
2015-02-04 23:07 ` Al Viro
2015-02-05 8:24 ` Robert Baldyga
2015-02-05 8:47 ` Al Viro
2015-02-05 9:03 ` Al Viro
2015-02-05 9:15 ` Robert Baldyga
[not found] ` <20150204230733.GK29656-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2015-02-05 15:29 ` Alan Stern
2015-02-06 7:03 ` Al Viro
[not found] ` <20150206070350.GX29656-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2015-02-06 8:44 ` Robert Baldyga
2015-02-07 5:44 ` Al Viro
2015-02-07 5:48 ` [PATCH 1/6] new helper: dup_iter() Al Viro
2015-02-07 5:48 ` [PATCH 2/6] gadget/function/f_fs.c: close leaks Al Viro
2015-02-07 5:48 ` [PATCH 3/6] gadget/function/f_fs.c: use put iov_iter into io_data Al Viro
2015-02-07 5:48 ` [PATCH 4/6] gadget/function/f_fs.c: switch to ->{read,write}_iter() Al Viro
2015-02-07 5:48 ` [PATCH 5/6] gadgetfs: use-after-free in ->aio_read() Al Viro
2015-02-07 5:48 ` [PATCH 6/6] gadget: switch ep_io_operations to ->read_iter/->write_iter Al Viro
2015-02-02 14:20 ` [PATCH 3/5] fs: remove ki_nbytes Christoph Hellwig
2015-01-27 17:55 ` [PATCH 4/5] fs: split generic and aio kiocb Christoph Hellwig
2015-01-27 17:55 ` [PATCH 5/5] fs: add async read/write interfaces Christoph Hellwig
2015-01-31 6:29 ` Al Viro
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