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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
Date: Thu, 10 Jan 2019 11:08:52 +0100
Message-ID: <f9ee08f81b3c114b015643e1fca5b7a9@suse.de> (raw)
In-Reply-To: <20190109165009.GM6310@bombadil.infradead.org>

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


  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09 16:40 [RFC 00/15] epoll: support pollable epoll from userspace Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 01/15] mm/vmalloc: add new 'alignment' field for vm_struct structure Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 02/15] mm/vmalloc: move common logic from __vmalloc_area_node to a separate func Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 03/15] mm/vmalloc: introduce new vrealloc() call and its subsidiary reach analog Roman Penyaev
2019-01-09 16:50   ` Matthew Wilcox
2019-01-10 10:08     ` Roman Penyaev [this message]
2019-01-09 16:40 ` [RFC PATCH 04/15] epoll: move private helpers from a header to the source Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 05/15] epoll: introduce user header structure and user index for polling from userspace Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 06/15] epoll: introduce various of helpers for user structure lengths calculations Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 07/15] epoll: extend epitem struct with new members for polling from userspace Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 08/15] epoll: some sanity flags checks for epoll syscalls for polled epfd " Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 09/15] epoll: introduce stand-alone helpers for polling " Roman Penyaev
2019-01-09 17:29   ` Linus Torvalds
2019-01-10 10:03     ` Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 10/15] epoll: support polling from userspace for ep_insert() Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 11/15] epoll: offload polling to a work in case of epfd polled from userspace Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 12/15] epoll: support polling from userspace for ep_remove() Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 13/15] epoll: support polling from userspace for ep_modify() Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 14/15] epoll: support polling from userspace for ep_poll() Roman Penyaev
2019-01-09 16:40 ` [RFC PATCH 15/15] epoll: support mapping for epfd when polled from userspace Roman Penyaev

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