linux-ext4 - Re: [PATCH 1/3] ext4: handle unwritten or delalloc buffers before enabling per-file data journaling

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Message-id: <172779421.90491448944976300.JavaMail.weblogic@epmlwas04c>
Date:	Tue, 01 Dec 2015 04:42:57 +0000 (GMT)
From:	Daeho Jeong <daeho.jeong@...sung.com>
To:	Jan Kara <jack@...e.cz>
Cc:	"tytso@....edu" <tytso@....edu>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	정대호 <daeho.jeong@...sung.com>
Subject: Re: [PATCH 1/3] ext4: handle unwritten or delalloc buffers before
 enabling per-file data journaling

Thank you, Jan.

> Can we maybe rephrase the whole comment like:
> 
> /* 
> * Before flushing the journal and switching inode's aops, we have
> * to flush all dirty data the inode has. There can be outstanding
> * delayed allocations, there can be unwritten extents created by
> * fallocate or buffered writes in dioread_nolock mode covered by
> * dirty data which can be converted only after flushing the dirty
> * data (and journalled aops don't know how to handle these cases).
> */

Your comment is more understandable, so I will change the comment in
the patch.

> BTW, the code is still racy wrt mmap write faults. Once Ted merges my
> patches for hole punching races, we need to grab i_mmap_sem for writing
> here as well to avoid write page fault from creating dirty page while we
> are switching aops... I'm mostly writing this here so that there's lower
> chance this gets lost.

Ok. I've recognized another racy condition when switching aops of an inode.
I will also consider the point in v2 of this patch.