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

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Message-ID: <CAKYAXd951bjgSkzFKOKigPx7Ut+=DPCUFQLdH-3DS-0mhp+f+Q@mail.gmail.com>
Date:	Fri, 14 Feb 2014 19:16:11 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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

2014-02-14 16:30 GMT+09:00, OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>:
> 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?
Right.
>
> So, I thought sync is not necessary.
Yes, I will add it as you pointed.

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