Re: [PATCH] f2fs: fix conflict between atomic_write and truncate

[Hou Pengyang <houpengyang@huawei.com>]

On 2016/12/13 3:18, Jaegeuk Kim wrote:
> Hi Pengyang,
>
Hi, kim,
> On 12/12, Hou Pengyang wrote:
>> In fsync_node_pages path, after locking the last_page for setting dirty,
>> we should check if the page has been truncated. Or there may be a mem leak,
>> as this dirty last_page will NOT be found in next page-cache travese.
>>
>> This patch adds page->mapping checking, and will NOT rewrite the page if
>> it has been truncated.
>>
>> Signed-off-by: Hou Pengyang <houpengyang@huawei.com>
>> ---
>>   fs/f2fs/node.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>> index c1bbfdc..78c5b50 100644
>> --- a/fs/f2fs/node.c
>> +++ b/fs/f2fs/node.c
>> @@ -1410,6 +1410,11 @@ int fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>>   			"Retry to write fsync mark: ino=%u, idx=%lx",
>>   					ino, last_page->index);
>>   		lock_page(last_page);
>
> We grabbed a reference count for this last_page, and thus, it won't be released.
> Something that I missed?
>
Some path (e.g. shrink) would NOT release the page if we've grabbed it,
But truncate operation will invalidate the page from page-cache
regardless of the page reference.

Patch: 0fac558b965 f2fs: make atomic/volatile operation exclusive
seems fix this issue by adding inode_lock(inode) to avoid conflict
between atomic/volatile and truncate operation.

But this patch makes codes more robust.

Thanks.

> Thanks,
>
>> +		if (unlikely(last_page->mapping != NODE_MAPPING(sbi))) {
>> +			unlock_page(last_page);
>> +			f2fs_put_page(last_page, 0);
>> +			goto out;
>> +		}
>>   		f2fs_wait_on_page_writeback(last_page, NODE, true);
>>   		set_page_dirty(last_page);
>>   		unlock_page(last_page);
>> --
>> 2.10.1
>>
>>
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>
> .
>



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