From: Vitaly Mayatskikh <v.mayatskih@gmail.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Vitaly Mayatskikh <v.mayatskih@gmail.com>,
Josef Bacik <josef@redhat.com>,
sandeen@redhat.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] Perform check in iov_iter_fault_in_readable() by check_readable_bytes()
Date: Fri, 15 May 2009 09:56:03 +0200 [thread overview]
Message-ID: <871vqqkdf0.wl%vmayatsk@redhat.com> (raw)
In-Reply-To: <87k54iq2gv.fsf@basil.nowhere.org>
At Fri, 15 May 2009 08:56:00 +0200, Andi Kleen wrote:
> Can you describe how it makes it POSIX friendly?
>
> My understanding was that EFAULT behaviour was undefined in POSIX.
>
> The obvious hole in the patch is that all these checks are not race
> free -- they don't pin pages -- so if there's a parallel unmap even
> with your change they can still fail in the middle.
ptr = mmap(0, page_size, ....);
...
write(fd, ptr + page_size - 256, 512);
Write() will fail here, but it can write first 256 bytes. Previously,
all 512 bytes were proceeded, but last 256 bytes were zeroed, and
sys_write() returned 256. Not very nice too.
--
wbr, Vitaly
next prev parent reply other threads:[~2009-05-15 7:56 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-14 16:18 [PATCH 0/2] sys_write() should write all valid data Vitaly Mayatskikh
2009-05-14 16:19 ` [PATCH 1/2] Introduce check_readable_bytes() Vitaly Mayatskikh
2009-05-14 17:40 ` Josef Bacik
2009-05-14 17:57 ` Vitaly Mayatskikh
2009-05-14 16:19 ` [PATCH 2/2] Perform check in iov_iter_fault_in_readable() by check_readable_bytes() Vitaly Mayatskikh
2009-05-15 6:56 ` Andi Kleen
2009-05-15 7:56 ` Vitaly Mayatskikh [this message]
2009-05-15 9:38 ` Andi Kleen
2009-05-15 11:56 ` Vitaly Mayatskikh
2009-05-15 12:19 ` Andi Kleen
2009-05-15 13:43 ` Jamie Lokier
2009-05-15 14:01 ` Andi Kleen
2009-05-15 14:37 ` Jamie Lokier
2009-05-18 8:31 ` Alan Cox
2009-05-18 9:48 ` Jamie Lokier
2009-05-18 10:03 ` Alan Cox
2009-05-18 10:16 ` Andi Kleen
2009-05-19 8:55 ` Pavel Machek
2009-05-14 18:02 ` [PATCH 0/2] sys_write() should write all valid data Josef Bacik
2009-05-14 18:48 ` Vitaly Mayatskikh
2009-05-14 19:05 ` Josef Bacik
2009-05-15 6:52 ` Andi Kleen
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