hugetlbfs: remove meaningless variable avoid_reserve

The variable avoid_reserve is meaningless because we never changed its
value and just passed it to alloc_huge_page().  So remove it to make code
more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
hugepage yet.  Also add a comment offered by Mike Kravetz to explain this.

Link: https://lkml.kernel.org/r/20210120071508.9078-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 974eee6736d22a084c049170f5c982f311f5f44c..7982adc3d98df00d4d864779eeb2f8f4c4ad9a28 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
                 */
                struct page *page;
                unsigned long addr;
-               int avoid_reserve = 0;
 
                cond_resched();
 
@@ -716,8 +715,15 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
                        continue;
                }
 
-               /* Allocate page and add to page cache */
-               page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
+               /*
+                * Allocate page without setting the avoid_reserve argument.
+                * There certainly are no reserves associated with the
+                * pseudo_vma.  However, there could be shared mappings with
+                * reserves for the file at the inode level.  If we fallocate
+                * pages in these areas, we need to consume the reserves
+                * to keep reservation accounting consistent.
+                */
+               page = alloc_huge_page(&pseudo_vma, addr, 0);
                hugetlb_drop_vma_policy(&pseudo_vma);
                if (IS_ERR(page)) {
                        mutex_unlock(&hugetlb_fault_mutex_table[hash]);