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SubjectRe: [PATCH] f2fs: fix to wait IO writeback in __revoke_inmem_pages()
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Ping,

On 2018/4/27 10:37, Chao Yu wrote:
> On 2018/4/27 0:36, Jaegeuk Kim wrote:
>> On 04/26, Chao Yu wrote:
>>> On 2018/4/26 23:48, Jaegeuk Kim wrote:
>>>> On 04/26, Chao Yu wrote:
>>>>> Thread A Thread B
>>>>> - f2fs_ioc_commit_atomic_write
>>>>> - commit_inmem_pages
>>>>> - f2fs_submit_merged_write_cond
>>>>> : write data
>>>>> - write_checkpoint
>>>>> - do_checkpoint
>>>>> : commit all node within CP
>>>>> -> SPO
>>>>> - f2fs_do_sync_file
>>>>> - file_write_and_wait_range
>>>>> : wait data writeback
>>>>>
>>>>> In above race condition, data/node can be flushed in reversed order when
>>>>> coming a checkpoint before f2fs_do_sync_file, after SPOR, it results in
>>>>> atomic written data being corrupted.
>>>>
>>>> Wait, what is the problem here? Thread B could succeed checkpoint, there is
>>>> no problem. If it fails, there is no fsync mark where we can recover it, so
>>>
>>> Node is flushed by checkpoint before data, with reversed order, that's the problem.
>>
>> What do you mean? Data should be in disk, in order to proceed checkpoint.
>
> 1. thread A: commit_inmem_pages submit data into block layer, but haven't waited
> it writeback.
> 2. thread A: commit_inmem_pages update related node.
> 3. thread B: do checkpoint, flush all nodes to disk
> 4. SPOR
>
> Then, atomic file becomes corrupted since nodes is flushed before data.
>
> Thanks,
>
>>
>>>
>>> Thanks,
>>>
>>>> we can just ignore the last written data as nothing.
>>>>
>>>>>
>>>>> This patch adds f2fs_wait_on_page_writeback in __revoke_inmem_pages() to
>>>>> keep data and node of atomic file being flushed orderly.
>>>>>
>>>>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>>>>> ---
>>>>> fs/f2fs/file.c | 4 ++++
>>>>> fs/f2fs/segment.c | 3 +++
>>>>> 2 files changed, 7 insertions(+)
>>>>>
>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>> index be7578774a47..a352804af244 100644
>>>>> --- a/fs/f2fs/file.c
>>>>> +++ b/fs/f2fs/file.c
>>>>> @@ -217,6 +217,9 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>>>>>
>>>>> trace_f2fs_sync_file_enter(inode);
>>>>>
>>>>> + if (atomic)
>>>>> + goto write_done;
>>>>> +
>>>>> /* if fdatasync is triggered, let's do in-place-update */
>>>>> if (datasync || get_dirty_pages(inode) <= SM_I(sbi)->min_fsync_blocks)
>>>>> set_inode_flag(inode, FI_NEED_IPU);
>>>>> @@ -228,6 +231,7 @@ static int f2fs_do_sync_file(struct file *file, loff_t start, loff_t end,
>>>>> return ret;
>>>>> }
>>>>>
>>>>> +write_done:
>>>>> /* if the inode is dirty, let's recover all the time */
>>>>> if (!f2fs_skip_inode_update(inode, datasync)) {
>>>>> f2fs_write_inode(inode, NULL);
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 584483426584..9ca3d0a43d93 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -230,6 +230,8 @@ static int __revoke_inmem_pages(struct inode *inode,
>>>>>
>>>>> lock_page(page);
>>>>>
>>>>> + f2fs_wait_on_page_writeback(page, DATA, true);
>>>>> +
>>>>> if (recover) {
>>>>> struct dnode_of_data dn;
>>>>> struct node_info ni;
>>>>> @@ -415,6 +417,7 @@ static int __commit_inmem_pages(struct inode *inode)
>>>>> /* drop all uncommitted pages */
>>>>> __revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>>>>> } else {
>>>>> + /* wait all committed IOs writeback and release them from list */
>>>>> __revoke_inmem_pages(inode, &revoke_list, false, false);
>>>>> }
>>>>>
>>>>> --
>>>>> 2.15.0.55.gc2ece9dc4de6
>>
>> .
>>
>
>
> .
>

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