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Date: Tue, 20 May 2008 10:16:23 +0800
From: "Dave Young" <hidave.darkstar@gmail.com>
To: "Alexey Dobriyan" <adobriyan@gmail.com>
Subject: Re: ext4-mm-delalloc-ext4-lock-reverse-fix
Cc: "Jiri Slaby" <jirislaby@gmail.com>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       linux-kernel@vger.kernel.org, "Mingming Cao" <cmm@us.ibm.com>
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On Tue, May 20, 2008 at 4:37 AM, Alexey Dobriyan <adobriyan@gmail.com> wrote:
> On Mon, May 19, 2008 at 05:24:47PM +0200, Jiri Slaby wrote:
>> Andrew Morton <akpm@linux-foundation.org> wrote:
>> > On Mon, 19 May 2008 15:15:09 +0800 "Dave Young" <hidave.darkstar@gmail.com> wrote:
>> >
>> > > With 2.6.26-rc2-mm1 I need to sync frequently. It's not normal as my
>> > > understanding.
>> > >
>> > > 1. scp a big file from a lan server. Firstly the speed is about 8M/s,
>> > > but the speed will slow down to 100K/s at last. After I exec "sync",
>> > > the speed will restore.
>> > >
>> > > Is this a known issue?
>> > >
>> >
>> > Yes, probably related to the "mkfs takes forever" problem.  I haven't
>> > looked into it yet.  Nor has anyone else afaik.
>>
>> Absolutely not sure what this breaks in ext4, but fixes the problem for me:

Jiri, it fixes my scp-slow-down problem as well. Thanks.

>
> This helps, thank you!
>
>> --- a/mm/page-writeback.c
>> +++ b/mm/page-writeback.c
>> @@ -881,7 +881,7 @@ int write_cache_pages(struct address_space *mapping,
>>       pagevec_init(&pvec, 0);
>>       if (wbc->range_cyclic) {
>>               index = mapping->writeback_index; /* Start from prev offset */
>> -             end = wbc->range_end >> PAGE_CACHE_SHIFT;
>> +             end = -1;
>>       } else {
>>               index = wbc->range_start >> PAGE_CACHE_SHIFT;
>>               end = wbc->range_end >> PAGE_CACHE_SHIFT;
>
>