* + mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch added to -mm tree
@ 2021-02-01 22:59 akpm
0 siblings, 0 replies; 2+ messages in thread
From: akpm @ 2021-02-01 22:59 UTC (permalink / raw)
To: dan.j.williams, david, iamjoonsoo.kim, ira.weiny, jgg, jgg,
jhubbard, jmorris, mgorman, mhocko, mhocko, mike.kravetz, mingo,
mm-commits, osalvador, pasha.tatashin, peterz, rientjes, rostedt,
sashal, tyhicks, vbabka, willy
The patch titled
Subject: mm/gup: check every subpage of a compound page during isolation
has been added to the -mm tree. Its filename is
mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Pavel Tatashin <pasha.tatashin@soleen.com>
Subject: mm/gup: check every subpage of a compound page during isolation
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.
Link: https://lkml.kernel.org/r/20210201153827.444374-3-pasha.tatashin@soleen.com
Fixes: aa712399c1e8 ("mm/gup: speed up check_and_migrate_cma_pages() on huge page")
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/gup.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
--- a/mm/gup.c~mm-gup-check-every-subpage-of-a-compound-page-during-isolation
+++ a/mm/gup.c
@@ -1549,26 +1549,23 @@ static long check_and_migrate_cma_pages(
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
@@ -1592,8 +1589,6 @@ check_again:
}
}
}
-
- i += step;
}
if (!list_empty(&cma_page_list)) {
_
Patches currently in -mm which might be from pasha.tatashin@soleen.com are
mm-gup-dont-pin-migrated-cma-pages-in-movable-zone.patch
mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
mm-gup-return-an-error-on-migration-failure.patch
mm-gup-check-for-isolation-errors.patch
mm-cma-rename-pf_memalloc_nocma-to-pf_memalloc_pin.patch
mm-apply-per-task-gfp-constraints-in-fast-path.patch
mm-honor-pf_memalloc_pin-for-all-movable-pages.patch
mm-gup-do-not-migrate-zero-page.patch
mm-gup-migrate-pinned-pages-out-of-movable-zone.patch
memory-hotplugrst-add-a-note-about-zone_movable-and-page-pinning.patch
mm-gup-change-index-type-to-long-as-it-counts-pages.patch
mm-gup-longterm-pin-migration-cleanup.patch
selftests-vm-gup_test-fix-test-flag.patch
selftests-vm-gup_test-test-faulting-in-kernel-and-verify-pinnable-pages.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
* + mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch added to -mm tree
@ 2021-03-08 21:30 akpm
0 siblings, 0 replies; 2+ messages in thread
From: akpm @ 2021-03-08 21:30 UTC (permalink / raw)
To: dan.j.williams, david, iamjoonsoo.kim, ira.weiny, jgg, jgg,
jhubbard, jmorris, mgorman, mhocko, mhocko, mike.kravetz, mingo,
mm-commits, osalvador, pasha.tatashin, peterz, rientjes, rostedt,
sashal, tyhicks, vbabka, willy
The patch titled
Subject: mm/gup: check every subpage of a compound page during isolation
has been added to the -mm tree. Its filename is
mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Pavel Tatashin <pasha.tatashin@soleen.com>
Subject: mm/gup: check every subpage of a compound page during isolation
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.
Link: https://lkml.kernel.org/r/20210215161349.246722-3-pasha.tatashin@soleen.com
Fixes: aa712399c1e8 ("mm/gup: speed up check_and_migrate_cma_pages() on huge page")
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/gup.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
--- a/mm/gup.c~mm-gup-check-every-subpage-of-a-compound-page-during-isolation
+++ a/mm/gup.c
@@ -1548,26 +1548,23 @@ static long check_and_migrate_cma_pages(
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
@@ -1591,8 +1588,6 @@ check_again:
}
}
}
-
- i += step;
}
if (!list_empty(&cma_page_list)) {
_
Patches currently in -mm which might be from pasha.tatashin@soleen.com are
mm-gup-dont-pin-migrated-cma-pages-in-movable-zone.patch
mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
mm-gup-return-an-error-on-migration-failure.patch
mm-gup-check-for-isolation-errors.patch
mm-cma-rename-pf_memalloc_nocma-to-pf_memalloc_pin.patch
mm-apply-per-task-gfp-constraints-in-fast-path.patch
mm-honor-pf_memalloc_pin-for-all-movable-pages.patch
mm-gup-do-not-migrate-zero-page.patch
mm-gup-migrate-pinned-pages-out-of-movable-zone.patch
memory-hotplugrst-add-a-note-about-zone_movable-and-page-pinning.patch
mm-gup-change-index-type-to-long-as-it-counts-pages.patch
mm-gup-longterm-pin-migration-cleanup.patch
selftests-vm-gup_test-fix-test-flag.patch
selftests-vm-gup_test-test-faulting-in-kernel-and-verify-pinnable-pages.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-02-01 22:59 + mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch added to -mm tree akpm
2021-03-08 21:30 akpm
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