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From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Gal Pressman <galpress@amazon.com>,
	Matthew Wilcox <willy@infradead.org>, Wei Zhang <wzam@amazon.com>,
	peterx@redhat.com, Mike Kravetz <mike.kravetz@oracle.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	David Gibson <david@gibson.dropbear.id.au>,
	Jason Gunthorpe <jgg@ziepe.ca>, Jann Horn <jannh@google.com>,
	Kirill Tkhai <ktkhai@virtuozzo.com>,
	Kirill Shutemov <kirill@shutemov.name>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Andrea Arcangeli <aarcange@redhat.com>, Jan Kara <jack@suse.cz>
Subject: [PATCH v5 2/5] hugetlg: Break earlier in add_reservation_in_range() when we can
Date: Wed, 17 Feb 2021 18:35:44 -0500	[thread overview]
Message-ID: <20210217233547.93892-3-peterx@redhat.com> (raw)
In-Reply-To: <20210217233547.93892-1-peterx@redhat.com>

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 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



  parent reply	other threads:[~2021-02-17 23:35 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-17 23:35 [PATCH v5 0/5] mm/hugetlb: Early cow on fork, and a few cleanups Peter Xu
2021-02-17 23:35 ` [PATCH v5 1/5] hugetlb: Dedup the code to add a new file_region Peter Xu
2021-02-17 23:35 ` Peter Xu [this message]
2021-02-17 23:35 ` [PATCH v5 3/5] mm: Introduce page_needs_cow_for_dma() for deciding whether cow Peter Xu
2021-02-17 23:35 ` [PATCH v5 4/5] mm: Use is_cow_mapping() across tree where proper Peter Xu
2021-02-17 23:35 ` [PATCH v5 5/5] hugetlb: Do early cow when page pinned on src mm Peter Xu
2021-03-01 14:11 ` [PATCH v5 0/5] mm/hugetlb: Early cow on fork, and a few cleanups Peter Xu
2021-03-02  0:28   ` Andrew Morton
2021-03-02  0:30     ` Jason Gunthorpe
2021-03-02  0:59       ` Zhang, Wei
2021-03-03  1:46     ` Peter Xu
2021-03-03  2:45       ` Linus Torvalds
2021-03-04 17:10         ` Jason Gunthorpe

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