Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII;
 format=flowed
Content-Transfer-Encoding: 7bit
Date:   Thu, 10 Jan 2019 11:08:52 +0100
From:   Roman Penyaev <rpenyaev@suse.de>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Joe Perches <joe@perches.com>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 03/15] mm/vmalloc: introduce new vrealloc() call and
 its subsidiary reach analog
In-Reply-To: <20190109165009.GM6310@bombadil.infradead.org>
References: <20190109164025.24554-1-rpenyaev@suse.de>
 <20190109164025.24554-4-rpenyaev@suse.de>
 <20190109165009.GM6310@bombadil.infradead.org>
Message-ID: <f9ee08f81b3c114b015643e1fca5b7a9@suse.de>
User-Agent: Roundcube Webmail
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2019-01-09 17:50, Matthew Wilcox wrote:
> On Wed, Jan 09, 2019 at 05:40:13PM +0100, Roman Penyaev wrote:
>> Basically vrealloc() repeats glibc realloc() with only one big 
>> difference:
>> old area is not freed, i.e. caller is responsible for calling vfree() 
>> in
>> case of successfull reallocation.
> 
> Ouch.  Don't call it the same thing when you're providing such 
> different
> semantics.  I agree with you that the new semantics are useful ones,
> I just want it called something else.  Maybe vcopy()?  vclone()?

vclone(). I like vclone().  But Linus does not like this reallocation
under the hood for epoll (where this vrealloc() should have been used),
so seems that won't be needed at all.

> 
>> + *	Do not forget to call vfree() passing old address.  But careful,
>> + *	calling vfree() from interrupt will cause vfree_deferred() call,
>> + *	which in its turn uses freed address as a temporal pointer for a
> 
> "temporary", not temporal.

Ha! Now I got the difference.  Thanks, Mathew :)

> 
>> + *	llist element, i.e. memory will be corrupted.

--
Roman