linux-kernel - Re: [f2fs-dev] [PATCH v2] f2fs: fix to read source block before invalidating it

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Message-ID: <91dbfa33-cda0-e6e7-d62f-6604939142d4@huawei.com>
Date:   Thu, 18 Jul 2019 14:16:29 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: fix to read source block before
 invalidating it

On 2019/7/18 12:00, Jaegeuk Kim wrote:
> On 07/18, Chao Yu wrote:
>> On 2019/7/18 11:12, Jaegeuk Kim wrote:
>>> f2fs_allocate_data_block() invalidates old block address and enable new block
>>> address. Then, if we try to read old block by f2fs_submit_page_bio(), it will
>>> give WARN due to reading invalid blocks.
>>>
>>> Let's make the order sanely back.
>>
>> Hmm.. to avoid WARM, we may suffer one more memcpy, I suspect this can reduce
>> online resize or foreground gc ioctl performance...
> 
> I worried about performance tho, more concern came to me that there may exist a
> chance that other thread can allocate and write something in old block address.

Me too, however, previous invalid block address should be reused after a
checkpoint, and checkpoint should have invalidated meta cache already, so there
shouldn't be any race here.

	/*
	 * invalidate intermediate page cache borrowed from meta inode
	 * which are used for migration of encrypted inode's blocks.
	 */
	if (f2fs_sb_has_encrypt(sbi))
		invalidate_mapping_pages(META_MAPPING(sbi),
				MAIN_BLKADDR(sbi), MAX_BLKADDR(sbi) - 1);

Thanks,

> 
>>
>> Can we just relief to use DATA_GENERIC_ENHANCE_READ for this case...?
> 
> We need to keep consistency for this api.
> 
> Thanks,
> 
>>
>>>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>
>> Except performance, I'm okay with this change.
>>
>> Reviewed-by: Chao Yu <yuchao0@...wei.com>
>>
>> Thanks,
>>
>>> ---
>>> v2:
>>> I was fixing the comments. :)
>>>
>>>  fs/f2fs/gc.c | 70 +++++++++++++++++++++++++---------------------------
>>>  1 file changed, 34 insertions(+), 36 deletions(-)
>>>
>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>> index 6691f526fa40..8974672db78f 100644
>>> --- a/fs/f2fs/gc.c
>>> +++ b/fs/f2fs/gc.c
>>> @@ -796,6 +796,29 @@ static int move_data_block(struct inode *inode, block_t bidx,
>>>  	if (lfs_mode)
>>>  		down_write(&fio.sbi->io_order_lock);
>>>  
>>> +	mpage = f2fs_grab_cache_page(META_MAPPING(fio.sbi),
>>> +					fio.old_blkaddr, false);
>>> +	if (!mpage)
>>> +		goto up_out;
>>> +
>>> +	fio.encrypted_page = mpage;
>>> +
>>> +	/* read source block in mpage */
>>> +	if (!PageUptodate(mpage)) {
>>> +		err = f2fs_submit_page_bio(&fio);
>>> +		if (err) {
>>> +			f2fs_put_page(mpage, 1);
>>> +			goto up_out;
>>> +		}
>>> +		lock_page(mpage);
>>> +		if (unlikely(mpage->mapping != META_MAPPING(fio.sbi) ||
>>> +						!PageUptodate(mpage))) {
>>> +			err = -EIO;
>>> +			f2fs_put_page(mpage, 1);
>>> +			goto up_out;
>>> +		}
>>> +	}
>>> +
>>>  	f2fs_allocate_data_block(fio.sbi, NULL, fio.old_blkaddr, &newaddr,
>>>  					&sum, CURSEG_COLD_DATA, NULL, false);
>>>  
>>> @@ -803,44 +826,18 @@ static int move_data_block(struct inode *inode, block_t bidx,
>>>  				newaddr, FGP_LOCK | FGP_CREAT, GFP_NOFS);
>>>  	if (!fio.encrypted_page) {
>>>  		err = -ENOMEM;
>>> -		goto recover_block;
>>> -	}
>>> -
>>> -	mpage = f2fs_pagecache_get_page(META_MAPPING(fio.sbi),
>>> -					fio.old_blkaddr, FGP_LOCK, GFP_NOFS);
>>> -	if (mpage) {
>>> -		bool updated = false;
>>> -
>>> -		if (PageUptodate(mpage)) {
>>> -			memcpy(page_address(fio.encrypted_page),
>>> -					page_address(mpage), PAGE_SIZE);
>>> -			updated = true;
>>> -		}
>>>  		f2fs_put_page(mpage, 1);
>>> -		invalidate_mapping_pages(META_MAPPING(fio.sbi),
>>> -					fio.old_blkaddr, fio.old_blkaddr);
>>> -		if (updated)
>>> -			goto write_page;
>>> -	}
>>> -
>>> -	err = f2fs_submit_page_bio(&fio);
>>> -	if (err)
>>> -		goto put_page_out;
>>> -
>>> -	/* write page */
>>> -	lock_page(fio.encrypted_page);
>>> -
>>> -	if (unlikely(fio.encrypted_page->mapping != META_MAPPING(fio.sbi))) {
>>> -		err = -EIO;
>>> -		goto put_page_out;
>>> -	}
>>> -	if (unlikely(!PageUptodate(fio.encrypted_page))) {
>>> -		err = -EIO;
>>> -		goto put_page_out;
>>> +		goto recover_block;
>>>  	}
>>>  
>>> -write_page:
>>> +	/* write target block */
>>>  	f2fs_wait_on_page_writeback(fio.encrypted_page, DATA, true, true);
>>> +	memcpy(page_address(fio.encrypted_page),
>>> +				page_address(mpage), PAGE_SIZE);
>>> +	f2fs_put_page(mpage, 1);
>>> +	invalidate_mapping_pages(META_MAPPING(fio.sbi),
>>> +				fio.old_blkaddr, fio.old_blkaddr);
>>> +
>>>  	set_page_dirty(fio.encrypted_page);
>>>  	if (clear_page_dirty_for_io(fio.encrypted_page))
>>>  		dec_page_count(fio.sbi, F2FS_DIRTY_META);
>>> @@ -871,11 +868,12 @@ static int move_data_block(struct inode *inode, block_t bidx,
>>>  put_page_out:
>>>  	f2fs_put_page(fio.encrypted_page, 1);
>>>  recover_block:
>>> -	if (lfs_mode)
>>> -		up_write(&fio.sbi->io_order_lock);
>>>  	if (err)
>>>  		f2fs_do_replace_block(fio.sbi, &sum, newaddr, fio.old_blkaddr,
>>>  								true, true);
>>> +up_out:
>>> +	if (lfs_mode)
>>> +		up_write(&fio.sbi->io_order_lock);
>>>  put_out:
>>>  	f2fs_put_dnode(&dn);
>>>  out:
>>>
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@...ts.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
> .
>