[PATCH] f2fs: avoid GC causing encrypted file corrupted

[PATCH] f2fs: avoid GC causing encrypted file corrupted

[Yunlong Song]

The encrypted file may be corrupted by GC in following case:

Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
segment 2,

Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |

Before page 1 is written back and if segment 2 become a victim, then
page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
during the GC process of Time 2, f2fs should wait for page 1 written back
before reading it, or move_data_block will read a garbage block from
blkaddr B since page is not written back to blkaddr B yet.

Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
ra_data_block to read encrypted block, but it forgets to add
f2fs_wait_on_page_writeback to avoid racing between GC and flush.

Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
---
 fs/f2fs/gc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index a4c1a41..c55fb62 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -641,6 +641,14 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
 	fio.page = page;
 	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
 
+	/*
+	 * don't cache encrypted data into meta inode until previous dirty
+	 * data were writebacked to avoid racing between GC and flush.
+	 */
+	f2fs_wait_on_page_writeback(page, DATA, true);
+
+	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
+
 	fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(sbi),
 					dn.data_blkaddr,
 					FGP_LOCK | FGP_CREAT, GFP_NOFS);
@@ -723,6 +731,8 @@ static void move_data_block(struct inode *inode, block_t bidx,
 	 */
 	f2fs_wait_on_page_writeback(page, DATA, true);
 
+	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
+
 	err = f2fs_get_node_info(fio.sbi, dn.nid, &ni);
 	if (err)
 		goto put_out;
-- 
1.8.5.2

Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

[Chao Yu]

On 2018/9/18 20:39, Yunlong Song wrote:
> The encrypted file may be corrupted by GC in following case:
> 
> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
> segment 2,
> 
> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |
> 
> Before page 1 is written back and if segment 2 become a victim, then
> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
> during the GC process of Time 2, f2fs should wait for page 1 written back
> before reading it, or move_data_block will read a garbage block from
> blkaddr B since page is not written back to blkaddr B yet.
> 
> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
> ra_data_block to read encrypted block, but it forgets to add
> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
> 
> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>

Reviewed-by: Chao Yu <yuchao0@huawei.com>

Thanks,

[PATCH] f2fs: avoid GC causing encrypted file corrupted

[Chao Yu]

Jaegeuk,

On 2018/9/18 21:21, Chao Yu wrote:
> On 2018/9/18 20:39, Yunlong Song wrote:
>> The encrypted file may be corrupted by GC in following case:
>>
>> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
>> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
>> segment 2,
>>
>> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |
>>
>> Before page 1 is written back and if segment 2 become a victim, then
>> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
>> during the GC process of Time 2, f2fs should wait for page 1 written back
>> before reading it, or move_data_block will read a garbage block from
>> blkaddr B since page is not written back to blkaddr B yet.
>>
>> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
>> ra_data_block to read encrypted block, but it forgets to add
>> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
>>
>> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> 
> Reviewed-by: Chao Yu <yuchao0@huawei.com>

I've reviewed this patch, could you add missing tag in the patch located in
dev-test branch?

Thanks,

> 
> Thanks,
> 
> .
> 

Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

[Jaegeuk Kim]

On 11/13, Chao Yu wrote:
> Jaegeuk,
> 
> On 2018/9/18 21:21, Chao Yu wrote:
> > On 2018/9/18 20:39, Yunlong Song wrote:
> >> The encrypted file may be corrupted by GC in following case:
> >>
> >> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
> >> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
> >> segment 2,
> >>
> >> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |
> >>
> >> Before page 1 is written back and if segment 2 become a victim, then
> >> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
> >> during the GC process of Time 2, f2fs should wait for page 1 written back
> >> before reading it, or move_data_block will read a garbage block from
> >> blkaddr B since page is not written back to blkaddr B yet.
> >>
> >> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
> >> ra_data_block to read encrypted block, but it forgets to add
> >> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
> >>
> >> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> > 
> > Reviewed-by: Chao Yu <yuchao0@huawei.com>
> 
> I've reviewed this patch, could you add missing tag in the patch located in
> dev-test branch?

Sorry, done.

> 
> Thanks,
> 
> > 
> > Thanks,
> > 
> > .
> > 

Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

[Jaegeuk Kim]

On 09/18, Yunlong Song wrote:
> The encrypted file may be corrupted by GC in following case:
> 
> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
> segment 2,
> 
> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |

            segment 2 blkaddr = B?

> 
> Before page 1 is written back and if segment 2 become a victim, then
> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,

                                                         C of ?

> during the GC process of Time 2, f2fs should wait for page 1 written back
> before reading it, or move_data_block will read a garbage block from
> blkaddr B since page is not written back to blkaddr B yet.

move_data_block() checks PageUptodate() so it won't get garbage, yes?
So, does ra_data_block need to check PageUptodate?

> 
> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
> ra_data_block to read encrypted block, but it forgets to add
> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
> 
> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> ---
>  fs/f2fs/gc.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index a4c1a41..c55fb62 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -641,6 +641,14 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>  	fio.page = page;
>  	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>  
> +	/*
> +	 * don't cache encrypted data into meta inode until previous dirty
> +	 * data were writebacked to avoid racing between GC and flush.
> +	 */
> +	f2fs_wait_on_page_writeback(page, DATA, true);
> +
> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
> +
>  	fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(sbi),
>  					dn.data_blkaddr,
>  					FGP_LOCK | FGP_CREAT, GFP_NOFS);
> @@ -723,6 +731,8 @@ static void move_data_block(struct inode *inode, block_t bidx,
>  	 */
>  	f2fs_wait_on_page_writeback(page, DATA, true);
>  
> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
> +
>  	err = f2fs_get_node_info(fio.sbi, dn.nid, &ni);
>  	if (err)
>  		goto put_out;
> -- 
> 1.8.5.2

Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

[Yunlong Song]

On 2018/9/19 2:17, Jaegeuk Kim wrote:
> On 09/18, Yunlong Song wrote:
>> The encrypted file may be corrupted by GC in following case:
>>
>> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
>> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
>> segment 2,
>>
>> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |
>              segment 2 blkaddr = B?
Sorry for typing error.
Yes.
>
>> Before page 1 is written back and if segment 2 become a victim, then
>> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
>                                                           C of ?
Yes.
>
>> during the GC process of Time 2, f2fs should wait for page 1 written back
>> before reading it, or move_data_block will read a garbage block from
>> blkaddr B since page is not written back to blkaddr B yet.
> move_data_block() checks PageUptodate() so it won't get garbage, yes?
> So, does ra_data_block need to check PageUptodate?
You mean if page 1 is read from blkaddr B before it is written back to 
blkaddr B, then
the page will become non-uptodate status, why? Is it because 
__read_end_io checks
"(bio->bi_status || PageError(page))" and ClearPageUptodate(page)?

>
>> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
>> ra_data_block to read encrypted block, but it forgets to add
>> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
>>
>> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
>> ---
>>   fs/f2fs/gc.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index a4c1a41..c55fb62 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -641,6 +641,14 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>>   	fio.page = page;
>>   	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>>   
>> +	/*
>> +	 * don't cache encrypted data into meta inode until previous dirty
>> +	 * data were writebacked to avoid racing between GC and flush.
>> +	 */
>> +	f2fs_wait_on_page_writeback(page, DATA, true);
>> +
>> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
>> +
>>   	fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(sbi),
>>   					dn.data_blkaddr,
>>   					FGP_LOCK | FGP_CREAT, GFP_NOFS);
>> @@ -723,6 +731,8 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>   	 */
>>   	f2fs_wait_on_page_writeback(page, DATA, true);
>>   
>> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
>> +
>>   	err = f2fs_get_node_info(fio.sbi, dn.nid, &ni);
>>   	if (err)
>>   		goto put_out;
>> -- 
>> 1.8.5.2
> .
>

-- 
Thanks,
Yunlong Song

Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

[Chao Yu]

On 2018/9/19 2:17, Jaegeuk Kim wrote:
> On 09/18, Yunlong Song wrote:
>> The encrypted file may be corrupted by GC in following case:
>>
>> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
>> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
>> segment 2,
>>
>> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |
> 
>             segment 2 blkaddr = B?
> 
>>
>> Before page 1 is written back and if segment 2 become a victim, then
>> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
> 
>                                                          C of ?
> 
>> during the GC process of Time 2, f2fs should wait for page 1 written back
>> before reading it, or move_data_block will read a garbage block from
>> blkaddr B since page is not written back to blkaddr B yet.
> 
> move_data_block() checks PageUptodate() so it won't get garbage, yes?

I think the problem here is:

Thread A				Background GC Thread
- writepage
 - f2fs_outplace_write_data
 fio->encrypted_page is in-flight
					- gc_data_segment
					 - ra_data_block
					  - f2fs_pagecache_get_page
					  - f2fs_submit_page_bio
					  cache garbage data in meta page
Device
Receive encrypted data
- f2fs_write_end_io
					 - move_data_block
					  - f2fs_pagecache_get_page
					  - if (PageUptodate(mpage)) memcpy()
					  So here we copy garbage data into meta page
					  - f2fs_submit_page_write
					  Here we migrate incorrect data to new address

> So, does ra_data_block need to check PageUptodate?

Yes, I think so, could improve this in another patch.

Thanks,

> 
>>
>> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
>> ra_data_block to read encrypted block, but it forgets to add
>> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
>>
>> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
>> ---
>>  fs/f2fs/gc.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index a4c1a41..c55fb62 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -641,6 +641,14 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>>  	fio.page = page;
>>  	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>>  
>> +	/*
>> +	 * don't cache encrypted data into meta inode until previous dirty
>> +	 * data were writebacked to avoid racing between GC and flush.
>> +	 */
>> +	f2fs_wait_on_page_writeback(page, DATA, true);
>> +
>> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
>> +
>>  	fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(sbi),
>>  					dn.data_blkaddr,
>>  					FGP_LOCK | FGP_CREAT, GFP_NOFS);
>> @@ -723,6 +731,8 @@ static void move_data_block(struct inode *inode, block_t bidx,
>>  	 */
>>  	f2fs_wait_on_page_writeback(page, DATA, true);
>>  
>> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
>> +
>>  	err = f2fs_get_node_info(fio.sbi, dn.nid, &ni);
>>  	if (err)
>>  		goto put_out;
>> -- 
>> 1.8.5.2

Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted

[Yunlong Song]

ping...

On 2018/9/18 20:39, Yunlong Song wrote:
> The encrypted file may be corrupted by GC in following case:
>
> Time 1: | segment 1 blkaddr = A |  GC -> | segment 2 blkaddr = B |
> Encrypted block 1 is moved from blkaddr A of segment 1 to blkaddr B of
> segment 2,
>
> Time 2: | segment 1 blkaddr = B |  GC -> | segment 3 blkaddr = C |
>
> Before page 1 is written back and if segment 2 become a victim, then
> page 1 is moved from blkaddr B of segment 2 to blkaddr Cof segment 3,
> during the GC process of Time 2, f2fs should wait for page 1 written back
> before reading it, or move_data_block will read a garbage block from
> blkaddr B since page is not written back to blkaddr B yet.
>
> Commit 6aa58d8a ("f2fs: readahead encrypted block during GC") introduce
> ra_data_block to read encrypted block, but it forgets to add
> f2fs_wait_on_page_writeback to avoid racing between GC and flush.
>
> Signed-off-by: Yunlong Song <yunlong.song@huawei.com>
> ---
>   fs/f2fs/gc.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index a4c1a41..c55fb62 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -641,6 +641,14 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
>   	fio.page = page;
>   	fio.new_blkaddr = fio.old_blkaddr = dn.data_blkaddr;
>   
> +	/*
> +	 * don't cache encrypted data into meta inode until previous dirty
> +	 * data were writebacked to avoid racing between GC and flush.
> +	 */
> +	f2fs_wait_on_page_writeback(page, DATA, true);
> +
> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
> +
>   	fio.encrypted_page = f2fs_pagecache_get_page(META_MAPPING(sbi),
>   					dn.data_blkaddr,
>   					FGP_LOCK | FGP_CREAT, GFP_NOFS);
> @@ -723,6 +731,8 @@ static void move_data_block(struct inode *inode, block_t bidx,
>   	 */
>   	f2fs_wait_on_page_writeback(page, DATA, true);
>   
> +	f2fs_wait_on_block_writeback(inode, dn.data_blkaddr);
> +
>   	err = f2fs_get_node_info(fio.sbi, dn.nid, &ni);
>   	if (err)
>   		goto put_out;

-- 
Thanks,
Yunlong Song