On Fri, Oct 30, 2015 at 04:32:12PM -0700, Mike Kravetz wrote:
> Hugh Dickins pointed out problems with the new hugetlbfs fallocate
> hole punch code. These problems are in the routine remove_inode_hugepages
> and mostly occur in the case where there are holes in the range of
> pages to be removed. These holes could be the result of a previous hole
> punch or simply sparse allocation.
>
> remove_inode_hugepages handles both hole punch and truncate operations.
> Page index handling was fixed/cleaned up so that holes are properly
> handled. In addition, code was changed to ensure multiple passes of the
> address range only happens in the truncate case. More comments were added
> to explain the different actions in each case. A cond_resched() was added
> after removing up to PAGEVEC_SIZE pages.
>
> Some totally unnecessary code in hugetlbfs_fallocate() that remained from
> early development was also removed.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
> fs/hugetlbfs/inode.c | 44 +++++++++++++++++++++++++++++---------------
> 1 file changed, 29 insertions(+), 15 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 316adb9..30cf534 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -368,10 +368,25 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> lookup_nr = end - next;
>
> /*
> - * This pagevec_lookup() may return pages past 'end',
> - * so we must check for page->index > end.
> + * When no more pages are found, take different action for
> + * hole punch and truncate.
> + *
> + * For hole punch, this indicates we have removed each page
> + * within the range and are done. Note that pages may have
> + * been faulted in after being removed in the hole punch case.
> + * This is OK as long as each page in the range was removed
> + * once.
> + *
> + * For truncate, we need to make sure all pages within the
> + * range are removed when exiting this routine. We could
> + * have raced with a fault that brought in a page after it
> + * was first removed. Check the range again until no pages
> + * are found.
> */
> if (!pagevec_lookup(&pvec, mapping, next, lookup_nr)) {
> + if (!truncate_op)
> + break;
> +
> if (next == start)
> break;
> next = start;
> @@ -382,19 +397,23 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> struct page *page = pvec.pages[i];
> u32 hash;
>
> + /*
> + * The page (index) could be beyond end. This is
> + * only possible in the punch hole case as end is
> + * LLONG_MAX for truncate.
> + */
> + if (page->index >= end) {
> + next = end; /* we are done */
> + break;
> + }
> + next = page->index;
> +
> hash = hugetlb_fault_mutex_hash(h, current->mm,
> &pseudo_vma,
> mapping, next, 0);
> mutex_lock(&hugetlb_fault_mutex_table[hash]);
>
> lock_page(page);
> - if (page->index >= end) {
> - unlock_page(page);
> - mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> - next = end; /* we are done */
> - break;
> - }
> -
> /*
> * If page is mapped, it was faulted in after being
> * unmapped. Do nothing in this race case. In the
> @@ -423,15 +442,13 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> }
> }
>
> - if (page->index > next)
> - next = page->index;
> -
> ++next;
You set next = page->index above, so this increment takes effect only in
the final iteration. Can we put this outside (just after) this for-loop?
Thanks,
Naoya Horiguchi
> unlock_page(page);
>
> mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> }
> huge_pagevec_release(&pvec);
> + cond_resched();
> }
>
> if (truncate_op)
> @@ -647,9 +664,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
> i_size_write(inode, offset + len);
> inode->i_ctime = CURRENT_TIME;
> - spin_lock(&inode->i_lock);
> - inode->i_private = NULL;
> - spin_unlock(&inode->i_lock);
> out:
> mutex_unlock(&inode->i_mutex);
> return error;
> --
> 2.4.3
>
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