linux-kernel - Re: [patch 3/3] fs: fix cont vs deadlock patches

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Message-ID: <87slfzu0ty.fsf@duaron.myhome.or.jp>
Date:	Fri, 01 Dec 2006 23:50:49 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andrew Morton <akpm@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [patch 3/3] fs: fix cont vs deadlock patches

Nick Piggin <npiggin@...e.de> writes:

>> >  		status = __block_prepare_write(inode, new_page, zerofrom,
>> >  						PAGE_CACHE_SIZE, get_block);
>> >  		if (status)
>> > @@ -2110,7 +2111,7 @@
>> >  		memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
>> >  		flush_dcache_page(new_page);
>> >  		kunmap_atomic(kaddr, KM_USER0);
>> > -		generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
>> > +		__block_commit_write(inode, new_page, zerofrom, PAGE_CACHE_SIZE);
>> 
>> Whatever function this is doesn't need to update i_size?
>
> Yes, it is the code in cont_prepare_write that is expanding a hole
> at the end of file.
>
> We can do this now because fat_commit_write is now changed to call
> generic_commit_write in the case of a non-zero length.
>
> I think it is an improvement because now the file will not get
> arbitrarily extended in the case of a write failure somewhere down
> the track.

Ah, unfortunately we can't this. If we don't update ->i_size before
page_cache_release, pdflush will think these pages is outside ->i_size
and just clean the page without writing it.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
-
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