linux-kernel - RE: [[PATCH v1] 15/37] [CIFS] SMBD: Post a SMBD data transfer message with data payload

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Date:   Wed, 30 Aug 2017 18:17:03 +0000
From:   Long Li <longli@...rosoft.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Steve French <sfrench@...ba.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "samba-technical@...ts.samba.org" <samba-technical@...ts.samba.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [[PATCH v1] 15/37] [CIFS] SMBD: Post a SMBD data transfer message
 with data payload

> -----Original Message-----
> From: Christoph Hellwig [mailto:hch@...radead.org]
> Sent: Wednesday, August 30, 2017 1:52 AM
> To: Long Li <longli@...rosoft.com>
> Cc: Christoph Hellwig <hch@...radead.org>; Steve French
> <sfrench@...ba.org>; linux-cifs@...r.kernel.org; samba-
> technical@...ts.samba.org; linux-kernel@...r.kernel.org
> Subject: Re: [[PATCH v1] 15/37] [CIFS] SMBD: Post a SMBD data transfer
> message with data payload
> 
> On Wed, Aug 30, 2017 at 02:17:56AM +0000, Long Li wrote:
> > I partially addressed this issue in the V3 patch. Most of the
> > duplicate code on sending path is merged.
> >
> > The difficulty with translating the buffer to pages is that: I don't
> > know how many pages will be translated, and how many struct page I
> > need to allocate in advance to hold them. I try to avoid memory
> > allocation in the I/O path as much as possible. So I keep two
> > functions of sending data: one for buffer and one for pages.
> 
> You do: you'll always need speace for  (len + PAGE_SIZE - 1) >> PAGE_SIZE
> pages.
> 
> That being said: what callers even send you buffers?  In general we should
> aim to work with pages for all allocations that aren't tiny.

I'll look through the code allocating the buffers, it probably can fit into one page. Will fix this.