The patch titled
Subject: memfd: fix F_SEAL_WRITE after shmem huge page allocated
has been removed from the -mm tree. Its filename was
memfd-fix-f_seal_write-after-shmem-huge-page-allocated.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: memfd: fix F_SEAL_WRITE after shmem huge page allocated
Wangyong reports: after enabling tmpfs filesystem to support transparent
hugepage with the following command:
echo always > /sys/kernel/mm/transparent_hugepage/shmem_enabled
the docker program tries to add F_SEAL_WRITE through the following
command, but it fails unexpectedly with errno EBUSY:
fcntl(5, F_ADD_SEALS, F_SEAL_WRITE) = -1.
That is because memfd_tag_pins() and memfd_wait_for_pins() were never
updated for shmem huge pages: checking page_mapcount() against
page_count() is hopeless on THP subpages - they need to check
total_mapcount() against page_count() on THP heads only.
Make memfd_tag_pins() (compared > 1) as strict as memfd_wait_for_pins()
(compared != 1): either can be justified, but given the non-atomic
total_mapcount() calculation, it is better now to be strict. Bear in mind
that total_mapcount() itself scans all of the THP subpages, when choosing
to take an XA_CHECK_SCHED latency break.
Also fix the unlikely xa_is_value() case in memfd_wait_for_pins(): if a
page has been swapped out since memfd_tag_pins(), then its refcount must
have fallen, and so it can safely be untagged.
Link: https://lkml.kernel.org/r/a4f79248-df75-2c8c-3df-ba3317ccb5da@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reported-by: Zeal Robot <zealci@xxxxxxxxxx>
Reported-by: wangyong <wang.yong12@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: CGEL ZTE <cgel.zte@xxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Cc: Yang Yang <yang.yang29@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memfd.c | 40 ++++++++++++++++++++++++++++------------
1 file changed, 28 insertions(+), 12 deletions(-)
--- a/mm/memfd.c~memfd-fix-f_seal_write-after-shmem-huge-page-allocated
+++ a/mm/memfd.c
@@ -31,20 +31,28 @@
static void memfd_tag_pins(struct xa_state *xas)
{
struct page *page;
- unsigned int tagged = 0;
+ int latency = 0;
+ int cache_count;
lru_add_drain();
xas_lock_irq(xas);
xas_for_each(xas, page, ULONG_MAX) {
- if (xa_is_value(page))
- continue;
- page = find_subpage(page, xas->xa_index);
- if (page_count(page) - page_mapcount(page) > 1)
+ cache_count = 1;
+ if (!xa_is_value(page) &&
+ PageTransHuge(page) && !PageHuge(page))
+ cache_count = HPAGE_PMD_NR;
+
+ if (!xa_is_value(page) &&
+ page_count(page) - total_mapcount(page) != cache_count)
xas_set_mark(xas, MEMFD_TAG_PINNED);
+ if (cache_count != 1)
+ xas_set(xas, page->index + cache_count);
- if (++tagged % XA_CHECK_SCHED)
+ latency += cache_count;
+ if (latency < XA_CHECK_SCHED)
continue;
+ latency = 0;
xas_pause(xas);
xas_unlock_irq(xas);
@@ -73,7 +81,8 @@ static int memfd_wait_for_pins(struct ad
error = 0;
for (scan = 0; scan <= LAST_SCAN; scan++) {
- unsigned int tagged = 0;
+ int latency = 0;
+ int cache_count;
if (!xas_marked(&xas, MEMFD_TAG_PINNED))
break;
@@ -87,10 +96,14 @@ static int memfd_wait_for_pins(struct ad
xas_lock_irq(&xas);
xas_for_each_marked(&xas, page, ULONG_MAX, MEMFD_TAG_PINNED) {
bool clear = true;
- if (xa_is_value(page))
- continue;
- page = find_subpage(page, xas.xa_index);
- if (page_count(page) - page_mapcount(page) != 1) {
+
+ cache_count = 1;
+ if (!xa_is_value(page) &&
+ PageTransHuge(page) && !PageHuge(page))
+ cache_count = HPAGE_PMD_NR;
+
+ if (!xa_is_value(page) && cache_count !=
+ page_count(page) - total_mapcount(page)) {
/*
* On the last scan, we clean up all those tags
* we inserted; but make a note that we still
@@ -103,8 +116,11 @@ static int memfd_wait_for_pins(struct ad
}
if (clear)
xas_clear_mark(&xas, MEMFD_TAG_PINNED);
- if (++tagged % XA_CHECK_SCHED)
+
+ latency += cache_count;
+ if (latency < XA_CHECK_SCHED)
continue;
+ latency = 0;
xas_pause(&xas);
xas_unlock_irq(&xas);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
tmpfs-support-for-file-creation-time-fix.patch
mm-_install_special_mapping-apply-vm_locked_clear_mask.patch
mm-thp-refix-__split_huge_pmd_locked-for-migration-pmd.patch
mm-thp-clearpagedoublemap-in-first-page_add_file_rmap.patch
mm-thp-fix-nr_file_mapped-accounting-in-page__file_rmap.patch
