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Date:   Mon, 29 Apr 2019 17:03:33 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] f2fs: introduce DATA_GENERIC_ENHANCE

On 2019/4/28 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.

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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