Pipe enum scan_result codes back through return values of functions
downstream of khugepaged_scan_file() and khugepaged_scan_pmd() to
inform callers if the operation was successful, and if not, why.
Since khugepaged_scan_pmd()'s return value already has a specific
meaning (whether mmap_lock was unlocked or not), add a bool* argument
to khugepaged_scan_pmd() to retrieve this information.
Change khugepaged to take action based on the return values of
khugepaged_scan_file() and khugepaged_scan_pmd() instead of acting
deep within the collapsing functions themselves.
hugepage_vma_revalidate() now returns SCAN_SUCCEED on success to be
more consistent with enum scan_result propagation.
Remove dependency on error pointers to communicate to khugepaged that
allocation failed and it should sleep; instead just use the result of
the scan (SCAN_ALLOC_HUGE_PAGE_FAIL if allocation fails).
Signed-off-by: Zach O'Keefe <zokeefe@xxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
---
mm/khugepaged.c | 233 ++++++++++++++++++++++++------------------------
1 file changed, 117 insertions(+), 116 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 8068adf24620..147f5828f052 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -558,7 +558,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
{
struct page *page = NULL;
pte_t *_pte;
- int none_or_zero = 0, shared = 0, result = 0, referenced = 0;
+ int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
bool writable = false;
for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
@@ -672,13 +672,13 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
result = SCAN_SUCCEED;
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
referenced, writable, result);
- return 1;
+ return result;
}
out:
release_pte_pages(pte, _pte, compound_pagelist);
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
referenced, writable, result);
- return 0;
+ return result;
}
static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
@@ -818,7 +818,6 @@ static bool khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
*hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
if (unlikely(!*hpage)) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
- *hpage = ERR_PTR(-ENOMEM);
return false;
}
@@ -830,8 +829,7 @@ static bool khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
/*
* If mmap_lock temporarily dropped, revalidate vma
* before taking mmap_lock.
- * Return 0 if succeeds, otherwise return none-zero
- * value (scan code).
+ * Returns enum scan_result value.
*/
static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
@@ -857,7 +855,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
*/
if (!vma->anon_vma || !vma_is_anonymous(vma))
return SCAN_VMA_CHECK;
- return 0;
+ return SCAN_SUCCEED;
}
/*
@@ -868,10 +866,10 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
* Note that if false is returned, mmap_lock will be released.
*/
-static bool __collapse_huge_page_swapin(struct mm_struct *mm,
- struct vm_area_struct *vma,
- unsigned long haddr, pmd_t *pmd,
- int referenced)
+static int __collapse_huge_page_swapin(struct mm_struct *mm,
+ struct vm_area_struct *vma,
+ unsigned long haddr, pmd_t *pmd,
+ int referenced)
{
int swapped_in = 0;
vm_fault_t ret = 0;
@@ -902,12 +900,13 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
*/
if (ret & VM_FAULT_RETRY) {
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
- return false;
+ /* Likely, but not guaranteed, that page lock failed */
+ return SCAN_PAGE_LOCK;
}
if (ret & VM_FAULT_ERROR) {
mmap_read_unlock(mm);
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
- return false;
+ return SCAN_FAIL;
}
swapped_in++;
}
@@ -917,7 +916,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
lru_add_drain();
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
- return true;
+ return SCAN_SUCCEED;
}
static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
@@ -935,17 +934,17 @@ static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
return SCAN_SUCCEED;
}
-static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
- struct page **hpage, int referenced,
- int unmapped, struct collapse_control *cc)
+static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
+ int referenced, int unmapped,
+ struct collapse_control *cc)
{
LIST_HEAD(compound_pagelist);
pmd_t *pmd, _pmd;
pte_t *pte;
pgtable_t pgtable;
- struct page *new_page;
+ struct page *hpage;
spinlock_t *pmd_ptl, *pte_ptl;
- int isolated = 0, result = 0;
+ int result = SCAN_FAIL;
struct vm_area_struct *vma;
struct mmu_notifier_range range;
@@ -959,15 +958,13 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
*/
mmap_read_unlock(mm);
- result = alloc_charge_hpage(hpage, mm, cc);
+ result = alloc_charge_hpage(&hpage, mm, cc);
if (result != SCAN_SUCCEED)
goto out_nolock;
- new_page = *hpage;
-
mmap_read_lock(mm);
result = hugepage_vma_revalidate(mm, address, &vma);
- if (result) {
+ if (result != SCAN_SUCCEED) {
mmap_read_unlock(mm);
goto out_nolock;
}
@@ -979,14 +976,16 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
goto out_nolock;
}
- /*
- * __collapse_huge_page_swapin will return with mmap_lock released
- * when it fails. So we jump out_nolock directly in that case.
- * Continuing to collapse causes inconsistency.
- */
- if (unmapped && !__collapse_huge_page_swapin(mm, vma, address,
- pmd, referenced)) {
- goto out_nolock;
+ if (unmapped) {
+ /*
+ * __collapse_huge_page_swapin will return with mmap_lock
+ * released when it fails. So we jump out_nolock directly in
+ * that case. Continuing to collapse causes inconsistency.
+ */
+ result = __collapse_huge_page_swapin(mm, vma, address, pmd,
+ referenced);
+ if (result != SCAN_SUCCEED)
+ goto out_nolock;
}
mmap_read_unlock(mm);
@@ -997,7 +996,7 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
*/
mmap_write_lock(mm);
result = hugepage_vma_revalidate(mm, address, &vma);
- if (result)
+ if (result != SCAN_SUCCEED)
goto out_up_write;
/* check if the pmd is still valid */
if (mm_find_pmd(mm, address) != pmd)
@@ -1024,11 +1023,11 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
mmu_notifier_invalidate_range_end(&range);
spin_lock(pte_ptl);
- isolated = __collapse_huge_page_isolate(vma, address, pte,
- &compound_pagelist);
+ result = __collapse_huge_page_isolate(vma, address, pte,
+ &compound_pagelist);
spin_unlock(pte_ptl);
- if (unlikely(!isolated)) {
+ if (unlikely(result != SCAN_SUCCEED)) {
pte_unmap(pte);
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
@@ -1040,7 +1039,6 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
pmd_populate(mm, pmd, pmd_pgtable(_pmd));
spin_unlock(pmd_ptl);
anon_vma_unlock_write(vma->anon_vma);
- result = SCAN_FAIL;
goto out_up_write;
}
@@ -1050,8 +1048,8 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
*/
anon_vma_unlock_write(vma->anon_vma);
- __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl,
- &compound_pagelist);
+ __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
+ &compound_pagelist);
pte_unmap(pte);
/*
* spin_lock() below is not the equivalent of smp_wmb(), but
@@ -1059,43 +1057,42 @@ static void collapse_huge_page(struct mm_struct *mm, unsigned long address,
* avoid the copy_huge_page writes to become visible after
* the set_pmd_at() write.
*/
- __SetPageUptodate(new_page);
+ __SetPageUptodate(hpage);
pgtable = pmd_pgtable(_pmd);
- _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
+ _pmd = mk_huge_pmd(hpage, vma->vm_page_prot);
_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
- page_add_new_anon_rmap(new_page, vma, address);
- lru_cache_add_inactive_or_unevictable(new_page, vma);
+ page_add_new_anon_rmap(hpage, vma, address);
+ lru_cache_add_inactive_or_unevictable(hpage, vma);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, address, pmd, _pmd);
update_mmu_cache_pmd(vma, address, pmd);
spin_unlock(pmd_ptl);
- *hpage = NULL;
+ hpage = NULL;
- khugepaged_pages_collapsed++;
result = SCAN_SUCCEED;
out_up_write:
mmap_write_unlock(mm);
out_nolock:
- if (!IS_ERR_OR_NULL(*hpage)) {
- mem_cgroup_uncharge(page_folio(*hpage));
- put_page(*hpage);
+ if (hpage) {
+ mem_cgroup_uncharge(page_folio(hpage));
+ put_page(hpage);
}
- trace_mm_collapse_huge_page(mm, isolated, result);
- return;
+ trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
+ return result;
}
static int khugepaged_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long address, struct page **hpage,
+ unsigned long address, bool *mmap_locked,
struct collapse_control *cc)
{
pmd_t *pmd;
pte_t *pte, *_pte;
- int ret = 0, result = 0, referenced = 0;
+ int result = SCAN_FAIL, referenced = 0;
int none_or_zero = 0, shared = 0;
struct page *page = NULL;
unsigned long _address;
@@ -1232,19 +1229,19 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
result = SCAN_LACK_REFERENCED_PAGE;
} else {
result = SCAN_SUCCEED;
- ret = 1;
}
out_unmap:
pte_unmap_unlock(pte, ptl);
- if (ret) {
+ if (result == SCAN_SUCCEED) {
+ result = collapse_huge_page(mm, address, referenced,
+ unmapped, cc);
/* collapse_huge_page will return with the mmap_lock released */
- collapse_huge_page(mm, address, hpage, referenced, unmapped,
- cc);
+ *mmap_locked = false;
}
out:
trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
none_or_zero, result, unmapped);
- return ret;
+ return result;
}
static void collect_mm_slot(struct mm_slot *mm_slot)
@@ -1506,7 +1503,6 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
* @mm: process address space where collapse happens
* @file: file that collapse on
* @start: collapse start address
- * @hpage: new allocated huge page for collapse
* @cc: collapse context and scratchpad
*
* Basic scheme is simple, details are more complex:
@@ -1524,12 +1520,11 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
* + restore gaps in the page cache;
* + unlock and free huge page;
*/
-static void collapse_file(struct mm_struct *mm, struct file *file,
- pgoff_t start, struct page **hpage,
- struct collapse_control *cc)
+static int collapse_file(struct mm_struct *mm, struct file *file,
+ pgoff_t start, struct collapse_control *cc)
{
struct address_space *mapping = file->f_mapping;
- struct page *new_page;
+ struct page *hpage;
pgoff_t index, end = start + HPAGE_PMD_NR;
LIST_HEAD(pagelist);
XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
@@ -1540,12 +1535,10 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
- result = alloc_charge_hpage(hpage, mm, cc);
+ result = alloc_charge_hpage(&hpage, mm, cc);
if (result != SCAN_SUCCEED)
goto out;
- new_page = *hpage;
-
/*
* Ensure we have slots for all the pages in the range. This is
* almost certainly a no-op because most of the pages must be present
@@ -1562,14 +1555,14 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
}
} while (1);
- __SetPageLocked(new_page);
+ __SetPageLocked(hpage);
if (is_shmem)
- __SetPageSwapBacked(new_page);
- new_page->index = start;
- new_page->mapping = mapping;
+ __SetPageSwapBacked(hpage);
+ hpage->index = start;
+ hpage->mapping = mapping;
/*
- * At this point the new_page is locked and not up-to-date.
+ * At this point the hpage is locked and not up-to-date.
* It's safe to insert it into the page cache, because nobody would
* be able to map it or use it in another way until we unlock it.
*/
@@ -1597,7 +1590,7 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
result = SCAN_FAIL;
goto xa_locked;
}
- xas_store(&xas, new_page);
+ xas_store(&xas, hpage);
nr_none++;
continue;
}
@@ -1739,19 +1732,19 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
list_add_tail(&page->lru, &pagelist);
/* Finally, replace with the new page. */
- xas_store(&xas, new_page);
+ xas_store(&xas, hpage);
continue;
out_unlock:
unlock_page(page);
put_page(page);
goto xa_unlocked;
}
- nr = thp_nr_pages(new_page);
+ nr = thp_nr_pages(hpage);
if (is_shmem)
- __mod_lruvec_page_state(new_page, NR_SHMEM_THPS, nr);
+ __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
else {
- __mod_lruvec_page_state(new_page, NR_FILE_THPS, nr);
+ __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
filemap_nr_thps_inc(mapping);
/*
* Paired with smp_mb() in do_dentry_open() to ensure
@@ -1762,21 +1755,21 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
smp_mb();
if (inode_is_open_for_write(mapping->host)) {
result = SCAN_FAIL;
- __mod_lruvec_page_state(new_page, NR_FILE_THPS, -nr);
+ __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr);
filemap_nr_thps_dec(mapping);
goto xa_locked;
}
}
if (nr_none) {
- __mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none);
+ __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
/* nr_none is always 0 for non-shmem. */
- __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none);
+ __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
}
/* Join all the small entries into a single multi-index entry */
xas_set_order(&xas, start, HPAGE_PMD_ORDER);
- xas_store(&xas, new_page);
+ xas_store(&xas, hpage);
xa_locked:
xas_unlock_irq(&xas);
xa_unlocked:
@@ -1798,11 +1791,11 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
index = start;
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
while (index < page->index) {
- clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ clear_highpage(hpage + (index % HPAGE_PMD_NR));
index++;
}
- copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
- page);
+ copy_highpage(hpage + (page->index % HPAGE_PMD_NR),
+ page);
list_del(&page->lru);
page->mapping = NULL;
page_ref_unfreeze(page, 1);
@@ -1813,23 +1806,22 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
index++;
}
while (index < end) {
- clear_highpage(new_page + (index % HPAGE_PMD_NR));
+ clear_highpage(hpage + (index % HPAGE_PMD_NR));
index++;
}
- SetPageUptodate(new_page);
- page_ref_add(new_page, HPAGE_PMD_NR - 1);
+ SetPageUptodate(hpage);
+ page_ref_add(hpage, HPAGE_PMD_NR - 1);
if (is_shmem)
- set_page_dirty(new_page);
- lru_cache_add(new_page);
+ set_page_dirty(hpage);
+ lru_cache_add(hpage);
/*
* Remove pte page tables, so we can re-fault the page as huge.
*/
retract_page_tables(mapping, start);
- *hpage = NULL;
-
- khugepaged_pages_collapsed++;
+ unlock_page(hpage);
+ hpage = NULL;
} else {
struct page *page;
@@ -1868,22 +1860,23 @@ static void collapse_file(struct mm_struct *mm, struct file *file,
VM_BUG_ON(nr_none);
xas_unlock_irq(&xas);
- new_page->mapping = NULL;
+ hpage->mapping = NULL;
}
- unlock_page(new_page);
+ if (hpage)
+ unlock_page(hpage);
out:
VM_BUG_ON(!list_empty(&pagelist));
- if (!IS_ERR_OR_NULL(*hpage)) {
- mem_cgroup_uncharge(page_folio(*hpage));
- put_page(*hpage);
+ if (hpage) {
+ mem_cgroup_uncharge(page_folio(hpage));
+ put_page(hpage);
}
/* TODO: tracepoints */
+ return result;
}
-static void khugepaged_scan_file(struct mm_struct *mm, struct file *file,
- pgoff_t start, struct page **hpage,
- struct collapse_control *cc)
+static int khugepaged_scan_file(struct mm_struct *mm, struct file *file,
+ pgoff_t start, struct collapse_control *cc)
{
struct page *page = NULL;
struct address_space *mapping = file->f_mapping;
@@ -1956,16 +1949,16 @@ static void khugepaged_scan_file(struct mm_struct *mm, struct file *file,
result = SCAN_EXCEED_NONE_PTE;
count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
} else {
- collapse_file(mm, file, start, hpage, cc);
+ result = collapse_file(mm, file, start, cc);
}
}
/* TODO: tracepoints */
+ return result;
}
#else
-static void khugepaged_scan_file(struct mm_struct *mm, struct file *file,
- pgoff_t start, struct page **hpage,
- struct collapse_control *cc)
+static int khugepaged_scan_file(struct mm_struct *mm, struct file *file,
+ pgoff_t start, struct collapse_control *cc)
{
BUILD_BUG();
}
@@ -1975,8 +1968,7 @@ static void khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot)
}
#endif
-static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
- struct page **hpage,
+static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
struct collapse_control *cc)
__releases(&khugepaged_mm_lock)
__acquires(&khugepaged_mm_lock)
@@ -1990,6 +1982,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
VM_BUG_ON(!pages);
lockdep_assert_held(&khugepaged_mm_lock);
+ *result = SCAN_FAIL;
if (khugepaged_scan.mm_slot)
mm_slot = khugepaged_scan.mm_slot;
@@ -2039,7 +2032,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
while (khugepaged_scan.address < hend) {
- int ret;
+ bool mmap_locked = true;
+
cond_resched();
if (unlikely(khugepaged_test_exit(mm)))
goto breakouterloop;
@@ -2053,20 +2047,28 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
khugepaged_scan.address);
mmap_read_unlock(mm);
- ret = 1;
- khugepaged_scan_file(mm, file, pgoff, hpage,
- cc);
+ *result = khugepaged_scan_file(mm, file, pgoff,
+ cc);
+ mmap_locked = false;
fput(file);
} else {
- ret = khugepaged_scan_pmd(mm, vma,
- khugepaged_scan.address,
- hpage, cc);
+ *result = khugepaged_scan_pmd(mm, vma,
+ khugepaged_scan.address,
+ &mmap_locked, cc);
}
+ if (*result == SCAN_SUCCEED)
+ ++khugepaged_pages_collapsed;
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
progress += HPAGE_PMD_NR;
- if (ret)
- /* we released mmap_lock so break loop */
+ if (!mmap_locked)
+ /*
+ * We released mmap_lock so break loop. Note
+ * that we drop mmap_lock before all hugepage
+ * allocations, so if allocation fails, we are
+ * guaranteed to break here and report the
+ * correct result back to caller.
+ */
goto breakouterloop_mmap_lock;
if (progress >= pages)
goto breakouterloop;
@@ -2118,10 +2120,10 @@ static int khugepaged_wait_event(void)
static void khugepaged_do_scan(struct collapse_control *cc)
{
- struct page *hpage = NULL;
unsigned int progress = 0, pass_through_head = 0;
unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
bool wait = true;
+ int result = SCAN_SUCCEED;
lru_add_drain_all();
@@ -2137,7 +2139,7 @@ static void khugepaged_do_scan(struct collapse_control *cc)
if (khugepaged_has_work() &&
pass_through_head < 2)
progress += khugepaged_scan_mm_slot(pages - progress,
- &hpage, cc);
+ &result, cc);
else
progress = pages;
spin_unlock(&khugepaged_mm_lock);
@@ -2145,7 +2147,7 @@ static void khugepaged_do_scan(struct collapse_control *cc)
if (progress >= pages)
break;
- if (IS_ERR(hpage)) {
+ if (result == SCAN_ALLOC_HUGE_PAGE_FAIL) {
/*
* If fail to allocate the first time, try to sleep for
* a while. When hit again, cancel the scan.
@@ -2153,7 +2155,6 @@ static void khugepaged_do_scan(struct collapse_control *cc)
if (!wait)
break;
wait = false;
- hpage = NULL;
khugepaged_alloc_sleep();
}
}
--
2.37.0.rc0.161.g10f37bed90-goog
