[RFC PATCH v2 16/18] mm: memcontrol: rename {un}lock_page_memcg() to {un}lock_page_objcg()

From: Muchun Song
Date: Fri Apr 09 2021 - 08:33:31 EST

Now the lock_page_memcg() does not lock a page and memcg binding, it
actually lock a page and objcg binding. So rename lock_page_memcg()
to lock_page_objcg().

This is just code cleanup without any functionality changes.

Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
Documentation/admin-guide/cgroup-v1/memory.rst | 2 +-
fs/buffer.c | 10 +++----
fs/iomap/buffered-io.c | 4 +--
include/linux/memcontrol.h | 18 +++++++----
mm/filemap.c | 2 +-
mm/huge_memory.c | 4 +--
mm/memcontrol.c | 41 ++++++++++++++++----------
mm/page-writeback.c | 24 +++++++--------
mm/rmap.c | 14 ++++-----
9 files changed, 67 insertions(+), 52 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
index 41191b5fb69d..dd582312b91a 100644
--- a/Documentation/admin-guide/cgroup-v1/memory.rst
+++ b/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -291,7 +291,7 @@ Lock order is as follows:

Page lock (PG_locked bit of page->flags)
mm->page_table_lock or split pte_lock
- lock_page_memcg (memcg->move_lock)
+ lock_page_objcg (memcg->move_lock)
mapping->i_pages lock
lruvec->lru_lock.

diff --git a/fs/buffer.c b/fs/buffer.c
index a542a47f6e27..6935f12d23f8 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -595,7 +595,7 @@ EXPORT_SYMBOL(mark_buffer_dirty_inode);
* If warn is true, then emit a warning if the page is not uptodate and has
* not been truncated.
*
- * The caller must hold lock_page_memcg().
+ * The caller must hold lock_page_objcg().
*/
void __set_page_dirty(struct page *page, struct address_space *mapping,
int warn)
@@ -660,14 +660,14 @@ int __set_page_dirty_buffers(struct page *page)
* Lock out page's memcg migration to keep PageDirty
* synchronized with per-memcg dirty page counters.
*/
- lock_page_memcg(page);
+ lock_page_objcg(page);
newly_dirty = !TestSetPageDirty(page);
spin_unlock(&mapping->private_lock);

if (newly_dirty)
__set_page_dirty(page, mapping, 1);

- unlock_page_memcg(page);
+ unlock_page_objcg(page);

if (newly_dirty)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
@@ -1164,13 +1164,13 @@ void mark_buffer_dirty(struct buffer_head *bh)
struct page *page = bh->b_page;
struct address_space *mapping = NULL;

- lock_page_memcg(page);
+ lock_page_objcg(page);
if (!TestSetPageDirty(page)) {
mapping = page_mapping(page);
if (mapping)
__set_page_dirty(page, mapping, 0);
}
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
if (mapping)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
}
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 414769a6ad11..106082a5109f 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -653,11 +653,11 @@ iomap_set_page_dirty(struct page *page)
* Lock out page's memcg migration to keep PageDirty
* synchronized with per-memcg dirty page counters.
*/
- lock_page_memcg(page);
+ lock_page_objcg(page);
newly_dirty = !TestSetPageDirty(page);
if (newly_dirty)
__set_page_dirty(page, mapping, 0);
- unlock_page_memcg(page);
+ unlock_page_objcg(page);

if (newly_dirty)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 8c56baacc255..35c83e49ac42 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -424,11 +424,12 @@ static inline struct obj_cgroup *page_objcg(struct page *page)
* proper memory cgroup pointer. It's not safe to call this function
* against some type of pages, e.g. slab pages or ex-slab pages.
*
- * For a page any of the following ensures page and objcg binding stability:
+ * For a page any of the following ensures page and objcg binding stability
+ * (But the page can be reparented to its parent memcg):
*
* - the page lock
* - LRU isolation
- * - lock_page_memcg()
+ * - lock_page_objcg()
* - exclusive reference
*
* Based on the stable binding of page and objcg, for a page any of the
@@ -948,8 +949,8 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);
extern bool cgroup_memory_noswap;
#endif

-void lock_page_memcg(struct page *page);
-void unlock_page_memcg(struct page *page);
+void lock_page_objcg(struct page *page);
+void unlock_page_objcg(struct page *page);

void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val);

@@ -1120,6 +1121,11 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,

struct mem_cgroup;

+static inline struct obj_cgroup *page_objcg(struct page *page)
+{
+ return NULL;
+}
+
static inline struct mem_cgroup *page_memcg(struct page *page)
{
return NULL;
@@ -1342,11 +1348,11 @@ mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
{
}

-static inline void lock_page_memcg(struct page *page)
+static inline void lock_page_objcg(struct page *page)
{
}

-static inline void unlock_page_memcg(struct page *page)
+static inline void unlock_page_objcg(struct page *page)
{
}

diff --git a/mm/filemap.c b/mm/filemap.c
index c03463cb72d6..aeb38953d68b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -110,7 +110,7 @@
* ->i_pages lock (page_remove_rmap->set_page_dirty)
* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
* ->inode->i_lock (page_remove_rmap->set_page_dirty)
- * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
+ * ->memcg->move_lock (page_remove_rmap->lock_page_objcg)
* bdi.wb->list_lock (zap_pte_range->set_page_dirty)
* ->inode->i_lock (zap_pte_range->set_page_dirty)
* ->private_lock (zap_pte_range->__set_page_dirty_buffers)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4c0a36dc67ea..d94cc7916253 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2306,7 +2306,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
atomic_inc(&page[i]._mapcount);
}

- lock_page_memcg(page);
+ lock_page_objcg(page);
if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
/* Last compound_mapcount is gone. */
__mod_lruvec_page_state(page, NR_ANON_THPS,
@@ -2317,7 +2317,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
atomic_dec(&page[i]._mapcount);
}
}
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
}

smp_wmb(); /* make pte visible before pmd */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 35a4c768dacc..403b0743338b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1311,7 +1311,7 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
* These functions are safe to use under any of the following conditions:
* - page locked
* - PageLRU cleared
- * - lock_page_memcg()
+ * - lock_page_objcg()
* - page->_refcount is zero
*/
struct lruvec *lock_page_lruvec(struct page *page)
@@ -2122,16 +2122,16 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
}

/**
- * lock_page_memcg - lock a page and memcg binding
+ * lock_page_objcg - lock a page and objcg binding
* @page: the page
*
* This function protects unlocked LRU pages from being moved to
* another cgroup.
*
- * It ensures lifetime of the locked memcg. Caller is responsible
+ * It ensures lifetime of the locked objcg. Caller is responsible
* for the lifetime of the page.
*/
-void lock_page_memcg(struct page *page)
+void lock_page_objcg(struct page *page)
{
struct page *head = compound_head(page); /* rmap on tail pages */
struct mem_cgroup *memcg;
@@ -2169,18 +2169,27 @@ void lock_page_memcg(struct page *page)
}

/*
+ * The cgroup migration and memory cgroup offlining are serialized by
+ * cgroup_mutex. If we reach here, it means that we are race with cgroup
+ * migration (or we are cgroup migration) and the @page cannot be
+ * reparented to its parent memory cgroup. So during the whole process
+ * from lock_page_objcg(page) to unlock_page_objcg(page), page_memcg(page)
+ * and obj_cgroup_memcg(objcg) are stable.
+ *
* When charge migration first begins, we can have multiple
* critical sections holding the fast-path RCU lock and one
* holding the slowpath move_lock. Track the task who has the
- * move_lock for unlock_page_memcg().
+ * move_lock for unlock_page_objcg().
*/
memcg->move_lock_task = current;
memcg->move_lock_flags = flags;
}
-EXPORT_SYMBOL(lock_page_memcg);
+EXPORT_SYMBOL(lock_page_objcg);

-static void __unlock_page_memcg(struct mem_cgroup *memcg)
+static void __unlock_page_objcg(struct obj_cgroup *objcg)
{
+ struct mem_cgroup *memcg = objcg ? obj_cgroup_memcg(objcg) : NULL;
+
if (memcg && memcg->move_lock_task == current) {
unsigned long flags = memcg->move_lock_flags;

@@ -2194,16 +2203,16 @@ static void __unlock_page_memcg(struct mem_cgroup *memcg)
}

/**
- * unlock_page_memcg - unlock a page and memcg binding
+ * unlock_page_objcg - unlock a page and objcg binding
* @page: the page
*/
-void unlock_page_memcg(struct page *page)
+void unlock_page_objcg(struct page *page)
{
struct page *head = compound_head(page);

- __unlock_page_memcg(page_memcg(head));
+ __unlock_page_objcg(page_objcg(head));
}
-EXPORT_SYMBOL(unlock_page_memcg);
+EXPORT_SYMBOL(unlock_page_objcg);

struct memcg_stock_pcp {
struct mem_cgroup *cached; /* this never be root cgroup */
@@ -2883,7 +2892,7 @@ static void commit_charge(struct page *page, struct obj_cgroup *objcg)
*
* - the page lock
* - LRU isolation
- * - lock_page_memcg()
+ * - lock_page_objcg()
* - exclusive reference
*/
page->memcg_data = (unsigned long)objcg;
@@ -5616,7 +5625,7 @@ static int mem_cgroup_move_account(struct page *page,
from_vec = mem_cgroup_lruvec(from, pgdat);
to_vec = mem_cgroup_lruvec(to, pgdat);

- lock_page_memcg(page);
+ lock_page_objcg(page);

if (PageAnon(page)) {
if (page_mapped(page)) {
@@ -5668,7 +5677,7 @@ static int mem_cgroup_move_account(struct page *page,
* with (un)charging, migration, LRU putback, or anything else
* that would rely on a stable page's memory cgroup.
*
- * Note that lock_page_memcg is a memcg lock, not a page lock,
+ * Note that lock_page_objcg is a memcg lock, not a page lock,
* to save space. As soon as we switch page's memory cgroup to a
* new memcg that isn't locked, the above state can change
* concurrently again. Make sure we're truly done with it.
@@ -5680,7 +5689,7 @@ static int mem_cgroup_move_account(struct page *page,

page->memcg_data = (unsigned long)to->objcg;

- __unlock_page_memcg(from);
+ __unlock_page_objcg(from->objcg);

ret = 0;

@@ -6122,7 +6131,7 @@ static void mem_cgroup_move_charge(void)
{
lru_add_drain_all();
/*
- * Signal lock_page_memcg() to take the memcg's move_lock
+ * Signal lock_page_objcg() to take the memcg's move_lock
* while we're moving its pages to another memcg. Then wait
* for already started RCU-only updates to finish.
*/
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0062d5c57d41..d5d9feb05a2e 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2413,7 +2413,7 @@ int __set_page_dirty_no_writeback(struct page *page)
/*
* Helper function for set_page_dirty family.
*
- * Caller must hold lock_page_memcg().
+ * Caller must hold lock_page_objcg().
*
* NOTE: This relies on being atomic wrt interrupts.
*/
@@ -2445,7 +2445,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
/*
* Helper function for deaccounting dirty page without writeback.
*
- * Caller must hold lock_page_memcg().
+ * Caller must hold lock_page_objcg().
*/
void account_page_cleaned(struct page *page, struct address_space *mapping,
struct bdi_writeback *wb)
@@ -2472,13 +2472,13 @@ void account_page_cleaned(struct page *page, struct address_space *mapping,
*/
int __set_page_dirty_nobuffers(struct page *page)
{
- lock_page_memcg(page);
+ lock_page_objcg(page);
if (!TestSetPageDirty(page)) {
struct address_space *mapping = page_mapping(page);
unsigned long flags;

if (!mapping) {
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
return 1;
}

@@ -2489,7 +2489,7 @@ int __set_page_dirty_nobuffers(struct page *page)
__xa_set_mark(&mapping->i_pages, page_index(page),
PAGECACHE_TAG_DIRTY);
xa_unlock_irqrestore(&mapping->i_pages, flags);
- unlock_page_memcg(page);
+ unlock_page_objcg(page);

if (mapping->host) {
/* !PageAnon && !swapper_space */
@@ -2497,7 +2497,7 @@ int __set_page_dirty_nobuffers(struct page *page)
}
return 1;
}
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
return 0;
}
EXPORT_SYMBOL(__set_page_dirty_nobuffers);
@@ -2630,14 +2630,14 @@ void __cancel_dirty_page(struct page *page)
struct bdi_writeback *wb;
struct wb_lock_cookie cookie = {};

- lock_page_memcg(page);
+ lock_page_objcg(page);
wb = unlocked_inode_to_wb_begin(inode, &cookie);

if (TestClearPageDirty(page))
account_page_cleaned(page, mapping, wb);

unlocked_inode_to_wb_end(inode, &cookie);
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
} else {
ClearPageDirty(page);
}
@@ -2724,7 +2724,7 @@ int test_clear_page_writeback(struct page *page)
struct address_space *mapping = page_mapping(page);
int ret;

- lock_page_memcg(page);
+ lock_page_objcg(page);
if (mapping && mapping_use_writeback_tags(mapping)) {
struct inode *inode = mapping->host;
struct backing_dev_info *bdi = inode_to_bdi(inode);
@@ -2756,7 +2756,7 @@ int test_clear_page_writeback(struct page *page)
dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
inc_node_page_state(page, NR_WRITTEN);
}
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
return ret;
}

@@ -2765,7 +2765,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
struct address_space *mapping = page_mapping(page);
int ret, access_ret;

- lock_page_memcg(page);
+ lock_page_objcg(page);
if (mapping && mapping_use_writeback_tags(mapping)) {
XA_STATE(xas, &mapping->i_pages, page_index(page));
struct inode *inode = mapping->host;
@@ -2805,7 +2805,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
inc_lruvec_page_state(page, NR_WRITEBACK);
inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
}
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
access_ret = arch_make_page_accessible(page);
/*
* If writeback has been triggered on a page that cannot be made
diff --git a/mm/rmap.c b/mm/rmap.c
index b0fc27e77d6d..3c2488e1081c 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -31,7 +31,7 @@
* swap_lock (in swap_duplicate, swap_info_get)
* mmlist_lock (in mmput, drain_mmlist and others)
* mapping->private_lock (in __set_page_dirty_buffers)
- * lock_page_memcg move_lock (in __set_page_dirty_buffers)
+ * lock_page_objcg move_lock (in __set_page_dirty_buffers)
* i_pages lock (widely used)
* lruvec->lru_lock (in lock_page_lruvec_irq)
* inode->i_lock (in set_page_dirty's __mark_inode_dirty)
@@ -1127,7 +1127,7 @@ void do_page_add_anon_rmap(struct page *page,
bool first;

if (unlikely(PageKsm(page)))
- lock_page_memcg(page);
+ lock_page_objcg(page);
else
VM_BUG_ON_PAGE(!PageLocked(page), page);

@@ -1155,7 +1155,7 @@ void do_page_add_anon_rmap(struct page *page,
}

if (unlikely(PageKsm(page))) {
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
return;
}

@@ -1215,7 +1215,7 @@ void page_add_file_rmap(struct page *page, bool compound)
int i, nr = 1;

VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page);
- lock_page_memcg(page);
+ lock_page_objcg(page);
if (compound && PageTransHuge(page)) {
int nr_pages = thp_nr_pages(page);

@@ -1244,7 +1244,7 @@ void page_add_file_rmap(struct page *page, bool compound)
}
__mod_lruvec_page_state(page, NR_FILE_MAPPED, nr);
out:
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
}

static void page_remove_file_rmap(struct page *page, bool compound)
@@ -1345,7 +1345,7 @@ static void page_remove_anon_compound_rmap(struct page *page)
*/
void page_remove_rmap(struct page *page, bool compound)
{
- lock_page_memcg(page);
+ lock_page_objcg(page);

if (!PageAnon(page)) {
page_remove_file_rmap(page, compound);
@@ -1384,7 +1384,7 @@ void page_remove_rmap(struct page *page, bool compound)
* faster for those pages still in swapcache.
*/
out:
- unlock_page_memcg(page);
+ unlock_page_objcg(page);
}

/*
--
2.11.0