linux-kernel - Re: [PATCH v3 2/6] fat: add fat

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Date:	Fri, 14 Feb 2014 16:30:19 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH v3 2/6] fat: add fat_fallocate operation

Namjae Jeon <linkinjeon@...il.com> writes:

>>> [...]
>>>
>>>> +		/* Release unwritten fallocated blocks on inode eviction. */
>>>> +		if (MSDOS_I(inode)->mmu_private < MSDOS_I(inode)->i_disksize) {
>>>> +			int err;
>>>> +			fat_truncate_blocks(inode, MSDOS_I(inode)->mmu_private);
>>>> +			/* Fallocate results in updating the i_start/iogstart
>>>> +			 * for the zero byte file. So, make it return to
>>>> +			 * original state during evict and commit it
>>>> +			 * synchrnously to avoid any corruption on the next
>>>> +			 * access to the cluster chain for the file.
>>>> +			 */
>>>> +			err = fat_sync_inode(inode);
>>>
>>> Ah, good catch. We have to update i_size. I was forgetting about this.
>>> Well, sync inode unconditionally would not be good. Maybe, we better to
>>> use __fat_write_inode() with inode_needs_sync() or such.
>> Okay, I will change it.
> Hi OGAWA
>
> When I checked more, we should wait till inode is sync. Because in the
> eviction it will leave the inode/buffers being marked dirty.
> Not waiting for it get sync over here. It will leave cluster chain
> corrupted when remounting.
> It mean we cannot use __fat_write_inode with inode_needs_sync() conditionally.

Yeah, this situation bothers us. However, the inode is not marked as
dirty after I_FREEING. And in fatfs case, all related dirty buffers
should goes into blockdev inode buffers (i.e. metadata only), right?

So, I thought sync is not necessary.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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