From: Greg Kurz <groug@kaod.org>
To: Dominique Martinet <asmadeus@codewreck.org>
Cc: v9fs-developer@lists.sourceforge.net,
linux-fsdevel@vger.kernel.org,
Matthew Wilcox <willy@infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: [V9fs-developer] [PATCH 1/2] net/9p: embed fcall in req to round down buffer allocs
Date: Wed, 1 Aug 2018 17:03:44 +0200 [thread overview]
Message-ID: <20180801170344.2ce3a762@bahia.lan> (raw)
In-Reply-To: <20180801143840.GA21463@nautica>
On Wed, 1 Aug 2018 16:38:40 +0200
Dominique Martinet <asmadeus@codewreck.org> wrote:
> Greg Kurz wrote on Wed, Aug 01, 2018:
> > > @@ -263,13 +261,13 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
> > > if (!req)
> > > return NULL;
> > >
> > > + if (p9_fcall_alloc(&req->tc, alloc_msize))
> > > + goto free;
> > > + if (p9_fcall_alloc(&req->rc, alloc_msize))
> > > goto free;
> >
> > Hmm... if the first allocation fails, we will kfree() req->rc.sdata.
> >
> > Are we sure we won't have a stale pointer or uninitialized data in
> > there ?
>
> Yeah, Jun pointed that out and I have a v2 that only frees as needed
> with an extra goto (I sent an incremental diff in my reply to his
> comment here[1])
>
> [1] https://lkml.kernel.org/r/20180731011256.GA30388@nautica
>
> > And even if we don't with the current code base, this is fragile and
> > could be easily broken.
> >
> > I think you should drop this hunk and rather rename p9_fcall_alloc() to
> > p9_fcall_alloc_sdata() instead, since this is what the function is
> > actually doing with this patch applied.
>
> Hmm. I agree the naming isn't accurate, but even if we rename it we'll
> need to pass a pointer to fcall as argument as it inits its capacity.
> p9_fcall_init(fc, msize) might be simpler?
>
Ah yes you're right... alloc is a bit misleading then. I agree that
p9_fcall_init() is more appropriate in this case.
And maybe you should introduce p9_fcall_fini() or _release() for
completeness. It would only do kfree() for a start, but it would
then evolve to be like the p9_fcall_kfree() function from patch 2.
> (I'm not sure I follow what you mean by 'drop this hunk', to be honest,
> did you want a single function call to init both maybe?)
>
I was meaning "keep the same logic in p9_tag_alloc()", something like:
req->tc.sdata = p9_fcall_alloc_sdata(&req->tc, alloc_msize);
req->rc.sdata = p9_fcall_alloc_sdata(&req->tc, alloc_msize);
if (!req->tc.sdata || !req->rc.sdata)
But I agree the way you did is cleaner.
next prev parent reply other threads:[~2018-08-01 17:07 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-11 21:02 [PATCH v2 0/6] 9p: Use IDRs more effectively Matthew Wilcox
2018-07-11 21:02 ` [PATCH v2 1/6] 9p: Fix comment on smp_wmb Matthew Wilcox
2018-07-12 11:55 ` [V9fs-developer] " Greg Kurz
2018-07-11 21:02 ` [PATCH v2 2/6] 9p: Change p9_fid_create calling convention Matthew Wilcox
2018-07-12 2:15 ` [V9fs-developer] " piaojun
2018-07-12 11:56 ` Greg Kurz
2018-07-13 1:18 ` jiangyiwen
2018-07-11 21:02 ` [PATCH v2 3/6] 9p: Replace the fidlist with an IDR Matthew Wilcox
2018-07-12 11:17 ` Dominique Martinet
2018-07-12 11:23 ` Matthew Wilcox
2018-07-12 11:30 ` Dominique Martinet
2018-07-13 2:05 ` [V9fs-developer] " jiangyiwen
2018-07-13 2:48 ` Matthew Wilcox
2018-07-11 21:02 ` [PATCH v2 4/6] 9p: Embed wait_queue_head into p9_req_t Matthew Wilcox
2018-07-12 14:36 ` [V9fs-developer] " Greg Kurz
2018-07-12 14:40 ` Dominique Martinet
2018-07-12 14:59 ` Greg Kurz
2018-07-11 21:02 ` [PATCH v2 5/6] 9p: Use a slab for allocating requests Matthew Wilcox
2018-07-18 10:05 ` Dominique Martinet
2018-07-18 11:49 ` Matthew Wilcox
2018-07-18 12:46 ` Dominique Martinet
2018-07-23 11:52 ` Greg Kurz
2018-07-23 12:25 ` Dominique Martinet
2018-07-23 14:24 ` Greg Kurz
2018-07-30 9:31 ` Dominique Martinet
2018-07-30 9:34 ` [PATCH 1/2] net/9p: embed fcall in req to round down buffer allocs Dominique Martinet
2018-07-30 9:34 ` [PATCH 2/2] net/9p: add a per-client fcall kmem_cache Dominique Martinet
2018-07-31 1:18 ` [V9fs-developer] " piaojun
2018-07-31 1:35 ` Dominique Martinet
2018-07-31 1:45 ` piaojun
2018-07-31 2:46 ` Matthew Wilcox
2018-07-31 4:17 ` Dominique Martinet
2018-08-01 14:28 ` [V9fs-developer] " Greg Kurz
2018-08-01 15:22 ` Dominique Martinet
2018-07-31 0:55 ` [V9fs-developer] [PATCH 1/2] net/9p: embed fcall in req to round down buffer allocs piaojun
2018-07-31 1:12 ` Dominique Martinet
2018-07-31 1:28 ` piaojun
2018-08-01 14:14 ` Greg Kurz
2018-08-01 14:38 ` Dominique Martinet
2018-08-01 15:03 ` Greg Kurz [this message]
2018-08-02 2:37 ` [PATCH v2 " Dominique Martinet
2018-08-02 2:37 ` [PATCH v2 2/2] net/9p: add a per-client fcall kmem_cache Dominique Martinet
2018-08-02 4:58 ` [V9fs-developer] " Dominique Martinet
2018-08-02 9:23 ` [PATCH v2 1/2] net/9p: embed fcall in req to round down buffer allocs Greg Kurz
2018-08-02 22:03 ` Dominique Martinet
2018-08-09 14:33 ` [PATCH v3 " Dominique Martinet
2018-08-09 14:33 ` [PATCH v3 2/2] net/9p: add a per-client fcall kmem_cache Dominique Martinet
2018-08-10 1:23 ` piaojun
2018-08-10 1:41 ` Dominique Martinet
2018-08-10 1:49 ` piaojun
2018-08-10 0:47 ` [PATCH v3 1/2] net/9p: embed fcall in req to round down buffer allocs piaojun
2018-07-11 21:02 ` [PATCH v2 6/6] 9p: Remove p9_idpool Matthew Wilcox
2018-07-11 23:37 ` [PATCH v2 0/6] 9p: Use IDRs more effectively Dominique Martinet
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