Re: [PATCH 3/3] hugetlbfs: remove unnecessary code after i_mmap_rwsem synchronization

[Aneesh Kumar K.V]

On 12/4/18 1:38 AM, Mike Kravetz wrote:
> After expanding i_mmap_rwsem use for better shared pmd and page fault/
> truncation synchronization, remove code that is no longer necessary.
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Fixes: ebed4bfc8da8 ("hugetlb: fix absurd HugePages_Rsvd")
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
>   fs/hugetlbfs/inode.c | 46 +++++++++++++++-----------------------------
>   mm/hugetlb.c         | 21 ++++++++++----------
>   2 files changed, 25 insertions(+), 42 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 3244147fc42b..a9c00c6ef80d 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -383,17 +383,16 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end)
>    * truncation is indicated by end of range being LLONG_MAX
>    *	In this case, we first scan the range and release found pages.
>    *	After releasing pages, hugetlb_unreserve_pages cleans up region/reserv
> - *	maps and global counts.  Page faults can not race with truncation
> - *	in this routine.  hugetlb_no_page() prevents page faults in the
> - *	truncated range.  It checks i_size before allocation, and again after
> - *	with the page table lock for the page held.  The same lock must be
> - *	acquired to unmap a page.
> + *	maps and global counts.
>    * hole punch is indicated if end is not LLONG_MAX
>    *	In the hole punch case we scan the range and release found pages.
>    *	Only when releasing a page is the associated region/reserv map
>    *	deleted.  The region/reserv map for ranges without associated
> - *	pages are not modified.  Page faults can race with hole punch.
> - *	This is indicated if we find a mapped page.
> + *	pages are not modified.
> + *
> + * Callers of this routine must hold the i_mmap_rwsem in write mode to prevent
> + * races with page faults.

Should this patch be merged to the previous one? Because the changes to 
callers are done in the previous patch.


> + *
>    * Note: If the passed end of range value is beyond the end of file, but
>    * not LLONG_MAX this routine still performs a hole punch operation.
>    */
> @@ -423,32 +422,14 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
>
>   		for (i = 0; i < pagevec_count(&pvec); ++i) {
-aneesh