Best wishes,
--
Ning Qu (曲宁) | Software Engineer | quning@xxxxxxxxxx | +1-408-418-6066
On Tue, Oct 15, 2013 at 4:01 AM, Kirill A. Shutemov
<kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> Ning Qu wrote:
>> When comes to truncate file, add support to handle huge page in the
>> truncate range.
>>
>> Signed-off-by: Ning Qu <quning@xxxxxxxxx>
>> ---
>> mm/shmem.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
>> 1 file changed, 86 insertions(+), 11 deletions(-)
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 0a423a9..90f2e0e 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -559,6 +559,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
>> struct shmem_inode_info *info = SHMEM_I(inode);
>> pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
>> pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
>> + /* Whether we have to do partial truncate */
>> unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
>> unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
>> struct pagevec pvec;
>> @@ -570,12 +571,16 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
>> if (lend == -1)
>> end = -1; /* unsigned, so actually very big */
>>
>> + i_split_down_read(inode);
>> pagevec_init(&pvec, 0);
>> index = start;
>> while (index < end) {
>> + bool thp = false;
>> +
>> pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
>> min(end - index, (pgoff_t)PAGEVEC_SIZE),
>> pvec.pages, indices);
>> +
>> if (!pvec.nr)
>> break;
>> mem_cgroup_uncharge_start();
>> @@ -586,6 +591,25 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
>> if (index >= end)
>> break;
>>
>> + thp = PageTransHugeCache(page);
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE
>
> Again. Here and below ifdef is redundant: PageTransHugeCache() is zero
> compile-time and thp case will be optimize out.
The problem is actually from HPAGE_CACHE_INDEX_MASK, it is marked as
build bug when CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE is false. So we
either wrap some logic inside a inline function, or we have to be like
this .. Or we don't treat the HPAGE_CACHE_INDEX_MASK as a build bug?
>
> And do we really need a copy of truncate logic here? Is there a way to
> share code?
>
The truncate between tmpfs and general one is similar but not exactly
the same (no readahead), so share the whole function might not be a
good choice from the perspective of tmpfs? Anyway, there are other
similar functions in tmpfs, e.g. the one you mentioned for
shmem_add_to_page_cache. It is possible to share the code, I am just
worried it will make the logic more complicated?
Maybe Hugh is in better position to judge on this? Thanks!
> --
> Kirill A. Shutemov
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