> On Jun 19, 2019, at 6:39 PM, Rik van Riel <riel@xxxxxx> wrote:
>
> On Tue, 2019-06-18 at 23:24 -0700, Song Liu wrote:
>
>> index 8563339041f6..bab8d9eef46c 100644
>> --- a/mm/truncate.c
>> +++ b/mm/truncate.c
>> @@ -790,7 +790,11 @@ EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
>> void truncate_pagecache(struct inode *inode, loff_t newsize)
>> {
>> struct address_space *mapping = inode->i_mapping;
>> - loff_t holebegin = round_up(newsize, PAGE_SIZE);
>> + loff_t holebegin;
>> +
>> + /* if non-shmem file has thp, truncate the whole file */
>> + if (filemap_nr_thps(mapping))
>> + newsize = 0;
>>
>
> I don't get it. Sometimes truncate is used to
> increase the size of a file, or to change it
> to a non-zero size.
>
> Won't forcing the newsize to zero break applications,
> when the file is truncated to a different size than
> they expect?
This is not truncate the file. It only drops page cache.
truncate_setsize() will still set correct size. I don't
think this breaks anything.
We can probably make it smarter and only drop the clean
huge pages (dirty page should not exist).
Thanks,
Song
