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Date:   Tue, 30 Apr 2019 11:18:43 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     Chao Yu <chao@...nel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] f2fs: introduce DATA_GENERIC_ENHANCE

On 2019/4/30 11:14, Jaegeuk Kim wrote:
> On 04/29, Chao Yu wrote:
>> On 2019/4/28 21:31, Jaegeuk Kim wrote:
>>> On 04/24, Chao Yu wrote:
>>>> On 2019-4-24 17:36, Jaegeuk Kim wrote:
>>>>> On 04/15, Chao Yu wrote:
>>>>>> Previously, f2fs_is_valid_blkaddr(, blkaddr, DATA_GENERIC) will check
>>>>>> whether @blkaddr locates in main area or not.
>>>>>>
>>>>>> That check is weak, since the block address in range of main area can
>>>>>> point to the address which is not valid in segment info table, and we
>>>>>> can not detect such condition, we may suffer worse corruption as system
>>>>>> continues running.
>>>>>>
>>>>>> So this patch introduce DATA_GENERIC_ENHANCE to enhance the sanity check
>>>>>> which trigger SIT bitmap check rather than only range check.
>>>>>>
>>>>>> This patch did below changes as wel:
>>>>>> - set SBI_NEED_FSCK in f2fs_is_valid_blkaddr().
>>>>>> - get rid of is_valid_data_blkaddr() to avoid panic if blkaddr is invalid.
>>>>>> - introduce verify_fio_blkaddr() to wrap fio {new,old}_blkaddr validation check.
>>>>>> - spread blkaddr check in:
>>>>>>  * f2fs_get_node_info()
>>>>>>  * __read_out_blkaddrs()
>>>>>>  * f2fs_submit_page_read()
>>>>>>  * ra_data_block()
>>>>>>  * do_recover_data()
>>>>>>
>>>>>> This patch can fix bug reported from bugzilla below:
>>>>>>
>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=203215
>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=203223
>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=203231
>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=203235
>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=203241
>>>>>
>>>>> Hi Chao,
>>>>>
>>>>> This introduces failures on xfstests/generic/446, and I'm testing the below
>>>>> patch on top of this. Could you check this patch, so that I could combine
>>>>> both of them?
>>>>>
>>>>> From 8c1808c1743ad75d1ad8d1dc5a53910edaf7afd7 Mon Sep 17 00:00:00 2001
>>>>> From: Jaegeuk Kim <jaegeuk@...nel.org>
>>>>> Date: Wed, 24 Apr 2019 00:21:07 +0100
>>>>> Subject: [PATCH] f2fs: consider data race on read and truncation on
>>>>>  DATA_GENERIC_ENHANCE
>>>>>
>>>>> DATA_GENERIC_ENHANCE enhanced to validate block addresses on read/write paths.
>>>>> But, xfstest/generic/446 compalins some generated kernel messages saying invalid
>>>>> bitmap was detected when reading a block. The reaons is, when we get the
>>>>> block addresses from extent_cache, there is no lock to synchronize it from
>>>>> truncating the blocks in parallel.
>>>>>
>>>>> This patch tries to return EFAULT without warning and setting SBI_NEED_FSCK
>>>>> in this case.
>>>>>
>>>>> Fixes: ("f2fs: introduce DATA_GENERIC_ENHANCE")
>>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>>>> ---
>>>>>  fs/f2fs/checkpoint.c | 35 ++++++++++++++++++-----------------
>>>>>  fs/f2fs/data.c       | 25 ++++++++++++++++++-------
>>>>>  fs/f2fs/f2fs.h       |  6 ++++++
>>>>>  fs/f2fs/gc.c         |  9 ++++++---
>>>>>  4 files changed, 48 insertions(+), 27 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>>>>> index e37fbbf843a5..805a33088e82 100644
>>>>> --- a/fs/f2fs/checkpoint.c
>>>>> +++ b/fs/f2fs/checkpoint.c
>>>>> @@ -130,26 +130,28 @@ struct page *f2fs_get_tmp_page(struct f2fs_sb_info *sbi, pgoff_t index)
>>>>>  	return __get_meta_page(sbi, index, false);
>>>>>  }
>>>>>  
>>>>> -static bool __is_bitmap_valid(struct f2fs_sb_info *sbi, block_t blkaddr)
>>>>> +static bool __is_bitmap_valid(struct f2fs_sb_info *sbi, block_t blkaddr,
>>>>> +							int type)
>>>>>  {
>>>>>  	struct seg_entry *se;
>>>>>  	unsigned int segno, offset;
>>>>>  	bool exist;
>>>>>  
>>>>> +	if (type != DATA_GENERIC_ENHANCE && type != DATA_GENERIC_ENHANCE_READ)
>>>>> +		return true;
>>>>> +
>>>>>  	segno = GET_SEGNO(sbi, blkaddr);
>>>>>  	offset = GET_BLKOFF_FROM_SEG0(sbi, blkaddr);
>>>>>  	se = get_seg_entry(sbi, segno);
>>>>>  
>>>>>  	exist = f2fs_test_bit(offset, se->cur_valid_map);
>>>>> -
>>>>> -	if (!exist) {
>>>>> +	if (!exist && type == DATA_GENERIC_ENHANCE) {
>>>>>  		f2fs_msg(sbi->sb, KERN_ERR, "Inconsistent error "
>>>>>  			"blkaddr:%u, sit bitmap:%d", blkaddr, exist);
>>>>>  		set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>>  		WARN_ON(1);
>>>>> -		return false;
>>>>>  	}
>>>>> -	return true;
>>>>> +	return exist;
>>>>>  }
>>>>>  
>>>>>  bool f2fs_is_valid_blkaddr(struct f2fs_sb_info *sbi,
>>>>> @@ -173,23 +175,22 @@ bool f2fs_is_valid_blkaddr(struct f2fs_sb_info *sbi,
>>>>>  			return false;
>>>>>  		break;
>>>>>  	case META_POR:
>>>>> +		if (unlikely(blkaddr >= MAX_BLKADDR(sbi) ||
>>>>> +			blkaddr < MAIN_BLKADDR(sbi)))
>>>>> +			return false;
>>>>> +		break;
>>>>>  	case DATA_GENERIC:
>>>>>  	case DATA_GENERIC_ENHANCE:
>>>>> +	case DATA_GENERIC_ENHANCE_READ:
>>>>>  		if (unlikely(blkaddr >= MAX_BLKADDR(sbi) ||
>>>>> -			blkaddr < MAIN_BLKADDR(sbi))) {
>>>>> -			if (type == DATA_GENERIC ||
>>>>> -				type == DATA_GENERIC_ENHANCE) {
>>>>> -				f2fs_msg(sbi->sb, KERN_WARNING,
>>>>> -					"access invalid blkaddr:%u", blkaddr);
>>>>> -				set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>> -				WARN_ON(1);
>>>>> -			}
>>>>> +				blkaddr < MAIN_BLKADDR(sbi))) {
>>>>> +			f2fs_msg(sbi->sb, KERN_WARNING,
>>>>> +				"access invalid blkaddr:%u", blkaddr);
>>>>> +			set_sbi_flag(sbi, SBI_NEED_FSCK);
>>>>> +			WARN_ON(1);
>>>>>  			return false;
>>>>>  		} else {
>>>>> -			if (type == DATA_GENERIC_ENHANCE) {
>>>>> -				if (!__is_bitmap_valid(sbi, blkaddr))
>>>>> -					return false;
>>>>> -			}
>>>>> +			return __is_bitmap_valid(sbi, blkaddr, type);
>>>>>  		}
>>>>>  		break;
>>>>>  	case META_GENERIC:
>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>>> index 34d248ac9e0f..d32a82f25f5a 100644
>>>>> --- a/fs/f2fs/data.c
>>>>> +++ b/fs/f2fs/data.c
>>>>> @@ -564,9 +564,6 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>>>>>  	struct bio_post_read_ctx *ctx;
>>>>>  	unsigned int post_read_steps = 0;
>>>>>  
>>>>> -	if (!f2fs_is_valid_blkaddr(sbi, blkaddr, DATA_GENERIC_ENHANCE))
>>>>> -		return ERR_PTR(-EFAULT);
>>>>> -
>>>>>  	bio = f2fs_bio_alloc(sbi, min_t(int, nr_pages, BIO_MAX_PAGES), false);
>>>>>  	if (!bio)
>>>>>  		return ERR_PTR(-ENOMEM);
>>>>> @@ -597,9 +594,6 @@ static int f2fs_submit_page_read(struct inode *inode, struct page *page,
>>>>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>>>>  	struct bio *bio;
>>>>>  
>>>>> -	if (!f2fs_is_valid_blkaddr(sbi, blkaddr, DATA_GENERIC_ENHANCE))
>>>>> -		return -EFAULT;
>>>>> -
>>>>>  	bio = f2fs_grab_read_bio(inode, blkaddr, 1, 0);
>>>>>  	if (IS_ERR(bio))
>>>>>  		return PTR_ERR(bio);
>>>>> @@ -741,6 +735,11 @@ struct page *f2fs_get_read_data_page(struct inode *inode, pgoff_t index,
>>>>>  
>>>>>  	if (f2fs_lookup_extent_cache(inode, index, &ei)) {
>>>>>  		dn.data_blkaddr = ei.blk + index - ei.fofs;
>>>>> +		if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), dn.data_blkaddr,
>>>>> +						DATA_GENERIC_ENHANCE_READ)) {
>>>>
>>>> If I'm not missing anything, we just need use DATA_GENERIC_ENHANCE_READ to cover
>>>> below two paths:
>>>> - gc_data_segment -> f2fs_get_read_data_page
>>>> - move_data_page -> f2fs_get_lock_data_page -> f2fs_get_read_data_page
>>>>
>>>> Other paths which calls f2fs_get_read_data_page is safe to verify blkaddr with
>>>> DATA_GENERIC_ENHANCE?
>>>
>>> The rule for here is, if block address is given by extent cache, we need to use
>>> ENHANCE_READ. If it's coming from dnode lock, I think it'd be safe.
>>
>> Okay, I tested this patch with below testcases from bugzilla, it seems there is
>> no regression.
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=203215
>> https://bugzilla.kernel.org/show_bug.cgi?id=203223
>> https://bugzilla.kernel.org/show_bug.cgi?id=203231
>> https://bugzilla.kernel.org/show_bug.cgi?id=203235
>> https://bugzilla.kernel.org/show_bug.cgi?id=203241
>>
>> One comment below.
>>
>>>
>>>>
>>>>> +			err = -EFAULT;
>>>>> +			goto put_err;
>>>>> +		}
>>>>>  		goto got_it;
>>>>>  	}
>>>>>  
>>>>> @@ -754,6 +753,13 @@ struct page *f2fs_get_read_data_page(struct inode *inode, pgoff_t index,
>>>>>  		err = -ENOENT;
>>>>>  		goto put_err;
>>>>>  	}
>>>>> +	if (dn.data_blkaddr != NEW_ADDR &&
>>>>> +			!f2fs_is_valid_blkaddr(F2FS_I_SB(inode),
>>>>> +						dn.data_blkaddr,
>>>>> +						DATA_GENERIC_ENHANCE)) {
>>>>> +		err = -EFAULT;
>>>>> +		goto put_err;
>>>>> +	}
>>>>>  got_it:
>>>>>  	if (PageUptodate(page)) {
>>>>>  		unlock_page(page);
>>>>> @@ -1566,7 +1572,7 @@ static int f2fs_read_single_page(struct inode *inode, struct page *page,
>>>>>  		}
>>>>>  
>>>>>  		if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), block_nr,
>>>>> -							DATA_GENERIC_ENHANCE)) {
>>>>> +						DATA_GENERIC_ENHANCE_READ)) {
>>>>>  			ret = -EFAULT;
>>>>>  			goto out;
>>>>>  		}
>>>>> @@ -2528,6 +2534,11 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
>>>>>  		zero_user_segment(page, 0, PAGE_SIZE);
>>>>>  		SetPageUptodate(page);
>>>>>  	} else {
>>>>> +		if (!f2fs_is_valid_blkaddr(sbi, blkaddr,
>>>>> +				DATA_GENERIC_ENHANCE_READ)) {
>>
>> Do we need to move the check into prepare_write_begin()? then we can know where
>> the block address comes from, and decide to use DATA_GENERIC_ENHANCE or
>> DATA_GENERIC_ENHANCE_READ.
> 
> That makes the code quite messy, since it requires to check NEW_ADDR/NULL_ADDR
> as well as extent_cache in much deeper f2fs_get_block.

Okay, we can keep it unless there is another bug reported in bugzilla.

Thanks,

> 
>>
>> Thanks,
>>
>>>>
>>>> Need DATA_GENERIC_ENHANCE because write() is exclusive with truncate() due to
>>>> inode_lock()?
>>>>
>>>> Thanks,
>>>>
>>>>> +			err = -EFAULT;
>>>>> +			goto fail;
>>>>> +		}
>>>>>  		err = f2fs_submit_page_read(inode, page, blkaddr);
>>>>>  		if (err)
>>>>>  			goto fail;
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index f5ffc09705eb..533fafca68f4 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -212,6 +212,12 @@ enum {
>>>>>  	META_POR,
>>>>>  	DATA_GENERIC,		/* check range only */
>>>>>  	DATA_GENERIC_ENHANCE,	/* strong check on range and segment bitmap */
>>>>> +	DATA_GENERIC_ENHANCE_READ,	/*
>>>>> +					 * strong check on range and segment
>>>>> +					 * bitmap but no warning due to race
>>>>> +					 * condition of read on truncated area
>>>>> +					 * by extent_cache
>>>>> +					 */
>>>>>  	META_GENERIC,
>>>>>  };
>>>>>  
>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>>>> index 3a097949b5d4..963fb4571fd9 100644
>>>>> --- a/fs/f2fs/gc.c
>>>>> +++ b/fs/f2fs/gc.c
>>>>> @@ -656,6 +656,11 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>>>>>  
>>>>>  	if (f2fs_lookup_extent_cache(inode, index, &ei)) {
>>>>>  		dn.data_blkaddr = ei.blk + index - ei.fofs;
>>>>> +		if (unlikely(!f2fs_is_valid_blkaddr(sbi, dn.data_blkaddr,
>>>>> +						DATA_GENERIC_ENHANCE_READ))) {
>>>>> +			err = -EFAULT;
>>>>> +			goto put_page;
>>>>> +		}
>>>>>  		goto got_it;
>>>>>  	}
>>>>>  
>>>>> @@ -669,14 +674,12 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>>>>>  		err = -ENOENT;
>>>>>  		goto put_page;
>>>>>  	}
>>>>> -
>>>>> -got_it:
>>>>>  	if (unlikely(!f2fs_is_valid_blkaddr(sbi, dn.data_blkaddr,
>>>>>  						DATA_GENERIC_ENHANCE))) {
>>>>>  		err = -EFAULT;
>>>>>  		goto put_page;
>>>>>  	}
>>>>> -
>>>>> +got_it:
>>>>>  	/* read page */
>>>>>  	fio.page = page;
>>>>>  	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>>>>>
>>> .
>>>
> .
> 

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