From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: pasha.tatashin@soleen.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz,
mhocko@suse.com, david@redhat.com, osalvador@suse.de,
dan.j.williams@intel.com, sashal@kernel.org,
tyhicks@linux.microsoft.com, iamjoonsoo.kim@lge.com,
mike.kravetz@oracle.com, rostedt@goodmis.org, mingo@redhat.com,
jgg@ziepe.ca, peterz@infradead.org, mgorman@suse.de,
willy@infradead.org, rientjes@google.com, jhubbard@nvidia.com,
linux-doc@vger.kernel.org, ira.weiny@intel.com,
linux-kselftest@vger.kernel.org, jmorris@namei.org
Subject: [PATCH v9 02/14] mm/gup: check every subpage of a compound page during isolation
Date: Mon, 1 Feb 2021 10:38:15 -0500 [thread overview]
Message-ID: <20210201153827.444374-3-pasha.tatashin@soleen.com> (raw)
In-Reply-To: <20210201153827.444374-1-pasha.tatashin@soleen.com>
When pages are isolated in check_and_migrate_movable_pages() we skip
compound number of pages at a time. However, as Jason noted, it is
not necessary correct that pages[i] corresponds to the pages that
we skipped. This is because it is possible that the addresses in
this range had split_huge_pmd()/split_huge_pud(), and these functions
do not update the compound page metadata.
The problem can be reproduced if something like this occurs:
1. User faulted huge pages.
2. split_huge_pmd() was called for some reason
3. User has unmapped some sub-pages in the range
4. User tries to longterm pin the addresses.
The resulting pages[i] might end-up having pages which are not compound
size page aligned.
Fixes: aa712399c1e8 ("mm/gup: speed up check_and_migrate_cma_pages() on huge page")
Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
---
mm/gup.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 24f25b1e9103..16f10d5a9eb6 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1556,26 +1556,23 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
unsigned int gup_flags)
{
unsigned long i;
- unsigned long step;
bool drain_allow = true;
bool migrate_allow = true;
LIST_HEAD(cma_page_list);
long ret = nr_pages;
+ struct page *prev_head, *head;
struct migration_target_control mtc = {
.nid = NUMA_NO_NODE,
.gfp_mask = GFP_USER | __GFP_NOWARN,
};
check_again:
- for (i = 0; i < nr_pages;) {
-
- struct page *head = compound_head(pages[i]);
-
- /*
- * gup may start from a tail page. Advance step by the left
- * part.
- */
- step = compound_nr(head) - (pages[i] - head);
+ prev_head = NULL;
+ for (i = 0; i < nr_pages; i++) {
+ head = compound_head(pages[i]);
+ if (head == prev_head)
+ continue;
+ prev_head = head;
/*
* If we get a page from the CMA zone, since we are going to
* be pinning these entries, we might as well move them out
@@ -1599,8 +1596,6 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
}
}
}
-
- i += step;
}
if (!list_empty(&cma_page_list)) {
--
2.25.1
next prev parent reply other threads:[~2021-02-01 15:40 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-01 15:38 [PATCH v9 00/14] prohibit pinning pages in ZONE_MOVABLE Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 01/14] mm/gup: don't pin migrated cma pages in movable zone Pavel Tatashin
2021-02-01 15:38 ` Pavel Tatashin [this message]
2021-02-01 15:38 ` [PATCH v9 03/14] mm/gup: return an error on migration failure Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 04/14] mm/gup: check for isolation errors Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 05/14] mm cma: rename PF_MEMALLOC_NOCMA to PF_MEMALLOC_PIN Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 06/14] mm: apply per-task gfp constraints in fast path Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 07/14] mm: honor PF_MEMALLOC_PIN for all movable pages Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 08/14] mm/gup: do not migrate zero page Pavel Tatashin
2021-02-02 2:41 ` kernel test robot
2021-02-02 4:05 ` Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 09/14] mm/gup: migrate pinned pages out of movable zone Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 10/14] memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 11/14] mm/gup: change index type to long as it counts pages Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 12/14] mm/gup: longterm pin migration cleanup Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 13/14] selftests/vm: gup_test: fix test flag Pavel Tatashin
2021-02-01 15:38 ` [PATCH v9 14/14] selftests/vm: gup_test: test faulting in kernel, and verify pinnable pages Pavel Tatashin
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