linux-kernel - [PATCH v5 2/5] hugetlg: Break earlier in add_reservation_in

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Date:   Wed, 17 Feb 2021 18:35:44 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Gal Pressman <galpress@...zon.com>,
        Matthew Wilcox <willy@...radead.org>,
        Wei Zhang <wzam@...zon.com>, peterx@...hat.com,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Christoph Hellwig <hch@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Jason Gunthorpe <jgg@...pe.ca>, Jann Horn <jannh@...gle.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        Kirill Shutemov <kirill@...temov.name>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Andrea Arcangeli <aarcange@...hat.com>, Jan Kara <jack@...e.cz>
Subject: [PATCH v5 2/5] hugetlg: Break earlier in add_reservation_in_range() when we can

All the regions maintained in hugetlb reserved map is inclusive on "from" but
exclusive on "to".  We can break earlier even if rg->from==t because it already
means no possible intersection.

This does not need a Fixes in all cases because when it happens (rg->from==t)
we'll not break out of the loop while we should, however the next thing we'd do
is still add the last file_region we'd need and quit the loop in the next
round.  So this change is not a bugfix (since the old code should still run
okay iiuc), but we'd better still touch it up to make it logically sane.

Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/hugetlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e302ed715839..2ba4ea4ab46e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -387,7 +387,7 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t,
 		/* When we find a region that starts beyond our range, we've
 		 * finished.
 		 */
-		if (rg->from > t)
+		if (rg->from >= t)
 			break;
 
 		/* Add an entry for last_accounted_offset -> rg->from, and
-- 
2.26.2