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From: Johannes Weiner <hannes@cmpxchg.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alex Shi <alex.shi@linux.alibaba.com>,
	Joonsoo Kim <js1304@gmail.com>,
	Shakeel Butt <shakeelb@google.com>,
	Hugh Dickins <hughd@google.com>, Michal Hocko <mhocko@suse.com>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Roman Gushchin <guro@fb.com>,
	linux-mm@kvack.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH 05/19] mm: memcontrol: convert page cache to a new mem_cgroup_charge() API
Date: Fri,  8 May 2020 14:30:52 -0400	[thread overview]
Message-ID: <20200508183105.225460-6-hannes@cmpxchg.org> (raw)
In-Reply-To: <20200508183105.225460-1-hannes@cmpxchg.org>

The try/commit/cancel protocol that memcg uses dates back to when
pages used to be uncharged upon removal from the page cache, and thus
couldn't be committed before the insertion had succeeded. Nowadays,
pages are uncharged when they are physically freed; it doesn't matter
whether the insertion was successful or not. For the page cache, the
transaction dance has become unnecessary.

Introduce a mem_cgroup_charge() function that simply charges a newly
allocated page to a cgroup and sets up page->mem_cgroup in one single
step. If the insertion fails, the caller doesn't have to do anything
but free/put the page.

Then switch the page cache over to this new API.

Subsequent patches will also convert anon pages, but it needs a bit
more prep work. Right now, memcg depends on page->mapping being
already set up at the time of charging, so that it can maintain its
own MEMCG_CACHE and MEMCG_RSS counters. For anon, page->mapping is set
under the same pte lock under which the page is publishd, so a single
charge point that can block doesn't work there just yet.

The following prep patches will replace the private memcg counters
with the generic vmstat counters, thus removing the page->mapping
dependency, then complete the transition to the new single-point
charge API and delete the old transactional scheme.

v2: leave shmem swapcache when charging fails to avoid double IO (Joonsoo)

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
---
 include/linux/memcontrol.h | 10 +++++
 mm/filemap.c               | 24 +++++------
 mm/memcontrol.c            | 29 ++++++++++++-
 mm/shmem.c                 | 88 ++++++++++++++++----------------------
 4 files changed, 85 insertions(+), 66 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 30292d57c8af..57339514d960 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -379,6 +379,10 @@ int mem_cgroup_try_charge_delay(struct page *page, struct mm_struct *mm,
 void mem_cgroup_commit_charge(struct page *page, struct mem_cgroup *memcg,
 			      bool lrucare);
 void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg);
+
+int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask,
+		      bool lrucare);
+
 void mem_cgroup_uncharge(struct page *page);
 void mem_cgroup_uncharge_list(struct list_head *page_list);
 
@@ -893,6 +897,12 @@ static inline void mem_cgroup_cancel_charge(struct page *page,
 {
 }
 
+static inline int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
+				    gfp_t gfp_mask, bool lrucare)
+{
+	return 0;
+}
+
 static inline void mem_cgroup_uncharge(struct page *page)
 {
 }
diff --git a/mm/filemap.c b/mm/filemap.c
index ce200386736c..ee9882509566 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -832,7 +832,6 @@ static int __add_to_page_cache_locked(struct page *page,
 {
 	XA_STATE(xas, &mapping->i_pages, offset);
 	int huge = PageHuge(page);
-	struct mem_cgroup *memcg;
 	int error;
 	void *old;
 
@@ -840,17 +839,16 @@ static int __add_to_page_cache_locked(struct page *page,
 	VM_BUG_ON_PAGE(PageSwapBacked(page), page);
 	mapping_set_update(&xas, mapping);
 
-	if (!huge) {
-		error = mem_cgroup_try_charge(page, current->mm,
-					      gfp_mask, &memcg);
-		if (error)
-			return error;
-	}
-
 	get_page(page);
 	page->mapping = mapping;
 	page->index = offset;
 
+	if (!huge) {
+		error = mem_cgroup_charge(page, current->mm, gfp_mask, false);
+		if (error)
+			goto error;
+	}
+
 	do {
 		xas_lock_irq(&xas);
 		old = xas_load(&xas);
@@ -874,20 +872,18 @@ static int __add_to_page_cache_locked(struct page *page,
 		xas_unlock_irq(&xas);
 	} while (xas_nomem(&xas, gfp_mask & GFP_RECLAIM_MASK));
 
-	if (xas_error(&xas))
+	if (xas_error(&xas)) {
+		error = xas_error(&xas);
 		goto error;
+	}
 
-	if (!huge)
-		mem_cgroup_commit_charge(page, memcg, false);
 	trace_mm_filemap_add_to_page_cache(page);
 	return 0;
 error:
 	page->mapping = NULL;
 	/* Leave page->index set: truncation relies upon it */
-	if (!huge)
-		mem_cgroup_cancel_charge(page, memcg);
 	put_page(page);
-	return xas_error(&xas);
+	return error;
 }
 ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO);
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8188d462d7ce..1d45a09b334f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6578,6 +6578,33 @@ void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg)
 	cancel_charge(memcg, nr_pages);
 }
 
+/**
+ * mem_cgroup_charge - charge a newly allocated page to a cgroup
+ * @page: page to charge
+ * @mm: mm context of the victim
+ * @gfp_mask: reclaim mode
+ * @lrucare: page might be on the LRU already
+ *
+ * Try to charge @page to the memcg that @mm belongs to, reclaiming
+ * pages according to @gfp_mask if necessary.
+ *
+ * Returns 0 on success. Otherwise, an error code is returned.
+ */
+int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask,
+		      bool lrucare)
+{
+	struct mem_cgroup *memcg;
+	int ret;
+
+	VM_BUG_ON_PAGE(!page->mapping, page);
+
+	ret = mem_cgroup_try_charge(page, mm, gfp_mask, &memcg);
+	if (ret)
+		return ret;
+	mem_cgroup_commit_charge(page, memcg, lrucare);
+	return 0;
+}
+
 struct uncharge_gather {
 	struct mem_cgroup *memcg;
 	unsigned long pgpgout;
@@ -6625,8 +6652,6 @@ static void uncharge_batch(const struct uncharge_gather *ug)
 static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 {
 	VM_BUG_ON_PAGE(PageLRU(page), page);
-	VM_BUG_ON_PAGE(page_count(page) && !is_zone_device_page(page) &&
-			!PageHWPoison(page) , page);
 
 	if (!page->mem_cgroup)
 		return;
diff --git a/mm/shmem.c b/mm/shmem.c
index d505b6cce4ab..afd5a057ebb7 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -605,11 +605,13 @@ static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
  */
 static int shmem_add_to_page_cache(struct page *page,
 				   struct address_space *mapping,
-				   pgoff_t index, void *expected, gfp_t gfp)
+				   pgoff_t index, void *expected, gfp_t gfp,
+				   struct mm_struct *charge_mm)
 {
 	XA_STATE_ORDER(xas, &mapping->i_pages, index, compound_order(page));
 	unsigned long i = 0;
 	unsigned long nr = compound_nr(page);
+	int error;
 
 	VM_BUG_ON_PAGE(PageTail(page), page);
 	VM_BUG_ON_PAGE(index != round_down(index, nr), page);
@@ -621,12 +623,22 @@ static int shmem_add_to_page_cache(struct page *page,
 	page->mapping = mapping;
 	page->index = index;
 
+	error = mem_cgroup_charge(page, charge_mm, gfp, PageSwapCache(page));
+	if (error) {
+		if (!PageSwapCache(page) && PageTransHuge(page)) {
+			count_vm_event(THP_FILE_FALLBACK);
+			count_vm_event(THP_FILE_FALLBACK_CHARGE);
+		}
+		goto error;
+	}
+	cgroup_throttle_swaprate(page, gfp);
+
 	do {
 		void *entry;
 		xas_lock_irq(&xas);
 		entry = xas_find_conflict(&xas);
 		if (entry != expected)
-			xas_set_err(&xas, -EEXIST);
+			xas_set_err(&xas, expected ? -ENOENT : -EEXIST);
 		xas_create_range(&xas);
 		if (xas_error(&xas))
 			goto unlock;
@@ -648,12 +660,15 @@ static int shmem_add_to_page_cache(struct page *page,
 	} while (xas_nomem(&xas, gfp));
 
 	if (xas_error(&xas)) {
-		page->mapping = NULL;
-		page_ref_sub(page, nr);
-		return xas_error(&xas);
+		error = xas_error(&xas);
+		goto error;
 	}
 
 	return 0;
+error:
+	page->mapping = NULL;
+	page_ref_sub(page, nr);
+	return error;
 }
 
 /*
@@ -1619,7 +1634,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 	struct address_space *mapping = inode->i_mapping;
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm;
-	struct mem_cgroup *memcg;
 	struct page *page;
 	swp_entry_t swap;
 	int error;
@@ -1664,29 +1678,23 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
 			goto failed;
 	}
 
-	error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg);
-	if (!error) {
-		error = shmem_add_to_page_cache(page, mapping, index,
-						swp_to_radix_entry(swap), gfp);
+	error = shmem_add_to_page_cache(page, mapping, index,
+					swp_to_radix_entry(swap), gfp,
+					charge_mm);
+	if (error) {
 		/*
-		 * We already confirmed swap under page lock, and make
-		 * no memory allocation here, so usually no possibility
-		 * of error; but free_swap_and_cache() only trylocks a
-		 * page, so it is just possible that the entry has been
-		 * truncated or holepunched since swap was confirmed.
+		 * We already confirmed swap under page lock, but
+		 * free_swap_and_cache() only trylocks a page, so it
+		 * is just possible that the entry has been truncated
+		 * or holepunched since swap was confirmed.
 		 * shmem_undo_range() will have done some of the
 		 * unaccounting, now delete_from_swap_cache() will do
 		 * the rest.
 		 */
-		if (error) {
-			mem_cgroup_cancel_charge(page, memcg);
+		if (error == -ENOENT)
 			delete_from_swap_cache(page);
-		}
-	}
-	if (error)
 		goto failed;
-
-	mem_cgroup_commit_charge(page, memcg, true);
+	}
 
 	spin_lock_irq(&info->lock);
 	info->swapped--;
@@ -1733,7 +1741,6 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	struct shmem_inode_info *info = SHMEM_I(inode);
 	struct shmem_sb_info *sbinfo;
 	struct mm_struct *charge_mm;
-	struct mem_cgroup *memcg;
 	struct page *page;
 	enum sgp_type sgp_huge = sgp;
 	pgoff_t hindex = index;
@@ -1858,21 +1865,11 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 	if (sgp == SGP_WRITE)
 		__SetPageReferenced(page);
 
-	error = mem_cgroup_try_charge_delay(page, charge_mm, gfp, &memcg);
-	if (error) {
-		if (PageTransHuge(page)) {
-			count_vm_event(THP_FILE_FALLBACK);
-			count_vm_event(THP_FILE_FALLBACK_CHARGE);
-		}
-		goto unacct;
-	}
 	error = shmem_add_to_page_cache(page, mapping, hindex,
-					NULL, gfp & GFP_RECLAIM_MASK);
-	if (error) {
-		mem_cgroup_cancel_charge(page, memcg);
+					NULL, gfp & GFP_RECLAIM_MASK,
+					charge_mm);
+	if (error)
 		goto unacct;
-	}
-	mem_cgroup_commit_charge(page, memcg, false);
 	lru_cache_add_anon(page);
 
 	spin_lock_irq(&info->lock);
@@ -2310,7 +2307,6 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 	struct address_space *mapping = inode->i_mapping;
 	gfp_t gfp = mapping_gfp_mask(mapping);
 	pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
-	struct mem_cgroup *memcg;
 	spinlock_t *ptl;
 	void *page_kaddr;
 	struct page *page;
@@ -2360,16 +2356,10 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 	if (unlikely(offset >= max_off))
 		goto out_release;
 
-	ret = mem_cgroup_try_charge_delay(page, dst_mm, gfp, &memcg);
-	if (ret)
-		goto out_release;
-
 	ret = shmem_add_to_page_cache(page, mapping, pgoff, NULL,
-						gfp & GFP_RECLAIM_MASK);
+				      gfp & GFP_RECLAIM_MASK, dst_mm);
 	if (ret)
-		goto out_release_uncharge;
-
-	mem_cgroup_commit_charge(page, memcg, false);
+		goto out_release;
 
 	_dst_pte = mk_pte(page, dst_vma->vm_page_prot);
 	if (dst_vma->vm_flags & VM_WRITE)
@@ -2390,11 +2380,11 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 	ret = -EFAULT;
 	max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
 	if (unlikely(offset >= max_off))
-		goto out_release_uncharge_unlock;
+		goto out_release_unlock;
 
 	ret = -EEXIST;
 	if (!pte_none(*dst_pte))
-		goto out_release_uncharge_unlock;
+		goto out_release_unlock;
 
 	lru_cache_add_anon(page);
 
@@ -2415,12 +2405,10 @@ static int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
 	ret = 0;
 out:
 	return ret;
-out_release_uncharge_unlock:
+out_release_unlock:
 	pte_unmap_unlock(dst_pte, ptl);
 	ClearPageDirty(page);
 	delete_from_page_cache(page);
-out_release_uncharge:
-	mem_cgroup_cancel_charge(page, memcg);
 out_release:
 	unlock_page(page);
 	put_page(page);
-- 
2.26.2



  parent reply	other threads:[~2020-05-08 18:32 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-08 18:30 [PATCH 00/19 V2] mm: memcontrol: charge swapin pages on instantiation Johannes Weiner
2020-05-08 18:30 ` [PATCH 01/19] mm: fix NUMA node file count error in replace_page_cache() Johannes Weiner
2020-05-18 11:18   ` Balbir Singh
2020-05-08 18:30 ` [PATCH 02/19] mm: memcontrol: fix stat-corrupting race in charge moving Johannes Weiner
2020-05-08 18:30 ` [PATCH 03/19] mm: memcontrol: drop @compound parameter from memcg charging API Johannes Weiner
2020-05-08 18:30 ` [PATCH 04/19] mm: memcontrol: move out cgroup swaprate throttling Johannes Weiner
2020-05-08 18:30 ` Johannes Weiner [this message]
2020-06-10 16:09   ` [PATCH 05/19] mm: memcontrol: convert page cache to a new mem_cgroup_charge() API Michal Hocko
2020-05-08 18:30 ` [PATCH 06/19] mm: memcontrol: prepare uncharging for removal of private page type counters Johannes Weiner
2020-05-08 18:30 ` [PATCH 07/19] mm: memcontrol: prepare move_account " Johannes Weiner
2020-05-08 18:30 ` [PATCH 08/19] mm: memcontrol: prepare cgroup vmstat infrastructure for native anon counters Johannes Weiner
2020-05-08 18:30 ` [PATCH 09/19] mm: memcontrol: switch to native NR_FILE_PAGES and NR_SHMEM counters Johannes Weiner
2020-06-10 16:42   ` Michal Hocko
2020-05-08 18:30 ` [PATCH 10/19] mm: memcontrol: switch to native NR_ANON_MAPPED counter Johannes Weiner
2020-05-08 18:30 ` [PATCH 11/19] mm: memcontrol: switch to native NR_ANON_THPS counter Johannes Weiner
2020-05-08 18:30 ` [PATCH 12/19] mm: memcontrol: convert anon and file-thp to new mem_cgroup_charge() API Johannes Weiner
2020-05-12 14:38   ` Qian Cai
2020-05-12 17:11     ` Qian Cai
2020-05-12 21:58     ` Johannes Weiner
2020-05-12 23:58       ` Qian Cai
2020-05-08 18:31 ` [PATCH 13/19] mm: memcontrol: drop unused try/commit/cancel charge API Johannes Weiner
2020-06-22 17:06   ` Ben Widawsky
2020-05-08 18:31 ` [PATCH 14/19] mm: memcontrol: prepare swap controller setup for integration Johannes Weiner
2020-05-08 18:31 ` [PATCH 15/19] mm: memcontrol: make swap tracking an integral part of memory control Johannes Weiner
2020-05-08 18:31 ` [PATCH 16/19] mm: memcontrol: charge swapin pages on instantiation Johannes Weiner
2020-06-11  9:35   ` Michal Hocko
2020-06-17  8:49     ` [PATCH for 5.8] mm: do_swap_page fix up the error code instantiation Michal Hocko
2020-06-17  9:02       ` Michal Hocko
2020-06-17 13:34         ` Johannes Weiner
2020-05-08 18:31 ` [PATCH 17/19] mm: memcontrol: document the new swap control behavior Johannes Weiner
2020-05-08 18:31 ` [PATCH 18/19] mm: memcontrol: delete unused lrucare handling Johannes Weiner
2020-05-08 18:31 ` [PATCH 19/19] mm: memcontrol: update page->mem_cgroup stability rules Johannes Weiner
2020-06-11  9:40   ` Michal Hocko
2020-05-13 11:30 ` [PATCH 00/19 V2] mm: memcontrol: charge swapin pages on instantiation Balbir Singh
2020-05-13 12:35   ` Johannes Weiner
2020-05-14 11:04     ` Balbir Singh

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