Re: [PATCH 2/4] fs/block_dev: always invalidate cleancache in invalidate_bdev()

[Andrey Ryabinin <aryabinin@virtuozzo.com>]

On 04/18/2017 09:51 PM, Nikolay Borisov wrote:
> 
> 
> On 14.04.2017 17:07, Andrey Ryabinin wrote:
>> invalidate_bdev() calls cleancache_invalidate_inode() iff ->nrpages != 0
>> which doen't make any sense.
>> Make invalidate_bdev() always invalidate cleancache data.
>>
>> Fixes: c515e1fd361c ("mm/fs: add hooks to support cleancache")
>> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> ---
>>  fs/block_dev.c | 11 +++++------
>>  1 file changed, 5 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/block_dev.c b/fs/block_dev.c
>> index e405d8e..7af4787 100644
>> --- a/fs/block_dev.c
>> +++ b/fs/block_dev.c
>> @@ -103,12 +103,11 @@ void invalidate_bdev(struct block_device *bdev)
>>  {
>>  	struct address_space *mapping = bdev->bd_inode->i_mapping;
>>  
>> -	if (mapping->nrpages == 0)
>> -		return;
>> -
>> -	invalidate_bh_lrus();
>> -	lru_add_drain_all();	/* make sure all lru add caches are flushed */
>> -	invalidate_mapping_pages(mapping, 0, -1);
>> +	if (mapping->nrpages) {
>> +		invalidate_bh_lrus();
>> +		lru_add_drain_all();	/* make sure all lru add caches are flushed */
>> +		invalidate_mapping_pages(mapping, 0, -1);
>> +	}
> 
> How is this different than the current code? You will only invalidate
> the mapping iff ->nrpages > 0 ( I assume it can't go down below 0) ?

The difference is that invalidate_bdev() now always calls cleancache_invalidate_inode()
(you won't see it in this diff, it's placed after this if(mapping->nrpages){} block,)

> Perhaps just remove the if altogether?
> 

Given that invalidate_mapping_pages() invalidates exceptional entries as well, it certainly doesn't look
right that we look only at mapping->nrpages and completely ignore ->nrexceptional.
So maybe removing if() would be a right thing to do. But I think that should be a separate patch as it would
fix a another bug probably introduced by commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")

My intention here was to fix only cleancache case.


>>  	/* 99% of the time, we don't need to flush the cleancache on the bdev.
>>  	 * But, for the strange corners, lets be cautious
>>  	 */
>>

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