mm/khugepaged: delay computation of hpage boundaries until use

Only compute hstart/hend once we've passed all checks that would cause
early return in madvise_collapse().

Link: https://lkml.kernel.org/r/20220720140603.1958773-4-zokeefe@google.com
Fixes: c9d968ffd9ba ("mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse")
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 66314506e3ee9e55da73989b1e141088454a9fc8..6eec731bb925f37c4ab695e7fe38f59bead83149 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2416,9 +2416,6 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
        if (!vma->anon_vma || !vma_is_anonymous(vma))
                return -EINVAL;
 
-       hstart = (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
-       hend = end & HPAGE_PMD_MASK;
-
        if (!hugepage_vma_check(vma, vma->vm_flags, false, false, false))
                return -EINVAL;
 
@@ -2431,6 +2428,9 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
        mmgrab(mm);
        lru_add_drain_all();
 
+       hstart = (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
+       hend = end & HPAGE_PMD_MASK;
+
        for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) {
                int result = SCAN_FAIL;