From: Yunlong Song <yunlong.song@huawei.com>
To: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: <chao@kernel.org>, <yuchao0@huawei.com>,
<yunlong.song@icloud.com>, <miaoxie@huawei.com>,
<bintian.wang@huawei.com>, <shengyong1@huawei.com>,
<heyunlei@huawei.com>, <linux-f2fs-devel@lists.sourceforge.net>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] f2fs: avoid GC causing encrypted file corrupted
Date: Wed, 19 Sep 2018 10:37:12 +0800 [thread overview]
Message-ID: <8f0e5fc7-cb22-47a0-30e8-4e3a25891e8b@huawei.com> (raw)
In-Reply-To: <20180918181705.GG91945@jaegeuk-macbookpro.roam.corp.google.com>
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
next prev parent reply other threads:[~2018-09-19 2:37 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-18 12:39 [PATCH] f2fs: avoid GC causing encrypted file corrupted Yunlong Song
2018-09-18 13:21 ` Chao Yu
2018-11-13 3:16 ` Chao Yu
2018-11-14 21:54 ` Jaegeuk Kim
2018-09-18 18:17 ` Jaegeuk Kim
2018-09-19 2:37 ` Yunlong Song [this message]
2018-09-21 14:20 ` Chao Yu
2018-10-24 8:07 ` Yunlong Song
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