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From:   Peter Xu <peterx@redhat.com>
To:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc:     Kirill Shutemov <kirill@shutemov.name>,
        Wei Zhang <wzam@amazon.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Matthew Wilcox <willy@infradead.org>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Andrea Arcangeli <aarcange@redhat.com>, peterx@redhat.com,
        Gal Pressman <galpress@amazon.com>, Jan Kara <jack@suse.cz>,
        Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        David Gibson <david@gibson.dropbear.id.au>,
        Christoph Hellwig <hch@lst.de>
Subject: [PATCH v2 2/4] hugetlg: Break earlier in add_reservation_in_range() when we can
Date:   Thu,  4 Feb 2021 09:50:31 -0500
Message-Id: <20210204145033.136755-3-peterx@redhat.com>
In-Reply-To: <20210204145033.136755-1-peterx@redhat.com>
References: <20210204145033.136755-1-peterx@redhat.com>
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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@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 mm/hugetlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d2859c2aecc9..9e6ea96bf33b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -377,7 +377,7 @@ 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