mm: working set fixes

PATCH In review Michal Hocko 2 participants 9 messages Oct 24, 2016

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Michal Hocko

author

2016-10-24 15:26 UTC #0 lore raw

cover mm: working set fixes

Hi Johannes,
this is my attempt to backport your 22f2ac51b6d6 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()") which has been marked for 3.15+ stable trees. There are 2 follow up fixes for this patch d3798ae8c6f3 ("mm: filemap: don't plant shadow entries without radix tree node") and 3ddf40e8c319 ("mm: filemap: fix mapping->nrpages double accounting in fuse") which are backported here as well.

This is not an area I would feel really strongly so I would highly appreciate if you could review these backports. The first two needed quite some tweaking.

Thanks!

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Michal Hocko

author

2016-10-24 15:26 UTC #1 lore raw

PATCH 1/3 mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()

From: Johannes Weiner <[email protected]>

Commit 22f2ac51b6d643666f4db093f13144f773ff3f3a upstream.

Antonio reports the following crash when using fuse under memory pressure:

kernel BUG at /build/linux-a2WvEb/linux-4.4.0/mm/workingset.c:346! invalid opcode: 0000 [#1] SMP

  Modules linked in: all of them
  CPU: 2 PID: 63 Comm: kswapd0 Not tainted 4.4.0-36-generic #55-Ubuntu
  Hardware name: System manufacturer System Product Name/P8H67-M PRO, BIOS 3904 04/27/2013
  task: ffff88040cae6040 ti: ffff880407488000 task.ti: ffff880407488000
  RIP: shadow_lru_isolate+0x181/0x190
  Call Trace:
    __list_lru_walk_one.isra.3+0x8f/0x130
    list_lru_walk_one+0x23/0x30
    scan_shadow_nodes+0x34/0x50
    shrink_slab.part.40+0x1ed/0x3d0
    shrink_zone+0x2ca/0x2e0
    kswapd+0x51e/0x990
    kthread+0xd8/0xf0
    ret_from_fork+0x3f/0x70

which corresponds to the following sanity check in the shadow node tracking:

  BUG_ON(node->count & RADIX_TREE_COUNT_MASK);

The workingset code tracks radix tree nodes that exclusively contain shadow entries of evicted pages in them, and this (somewhat obscure) line checks whether there are real pages left that would interfere with reclaim of the radix tree node under memory pressure.

While discussing ways how fuse might sneak pages into the radix tree past the workingset code, Miklos pointed to replace_page_cache_page(), and indeed there is a problem there: it properly accounts for the old page being removed - __delete_from_page_cache() does that - but then does a raw raw radix_tree_insert(), not accounting for the replacement page. Eventually the page count bits in node->count underflow while leaving the node incorrectly linked to the shadow node LRU.

To address this, make sure replace_page_cache_page() uses the tracked page insertion code, page_cache_tree_insert(). This fixes the page accounting and makes sure page-containing nodes are properly unlinked from the shadow node LRU again.

Also, make the sanity checks a bit less obscure by using the helpers for checking the number of pages and shadows in a radix tree node.

Fixes 449dd6984d0e ("mm: keep page cache radix tree nodes in check")

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Johannes Weiner <[email protected]>

Reported-by Antonio SJ Musumeci <[email protected]>

Debugged-by Miklos Szeredi <[email protected]>

Cc <[email protected]> [3.15+]

Signed-off-by Andrew Morton <[email protected]>

Signed-off-by Linus Torvalds <[email protected]>

Signed-off-by Michal Hocko <[email protected]>

---
 include/linux/swap.h |  2 ++
 mm/filemap.c         | 86 ++++++++++++++++++++++++++--------------------------
 mm/workingset.c      | 10 +++---
 3 files changed, 49 insertions(+), 49 deletions(-)

include/linux/swap.h +2 -0

index 7ba7dccaf0e7..b28de19aadbf 100644
@@ -266,6 +266,7 @@ static inline void workingset_node_pages_inc(struct radix_tree_node *node)
 
 static inline void workingset_node_pages_dec(struct radix_tree_node *node)
 {
+	VM_BUG_ON(!workingset_node_pages(node));
 	node->count--;
 }

@@ -281,6 +282,7 @@ static inline void workingset_node_shadows_inc(struct radix_tree_node *node)
 
 static inline void workingset_node_shadows_dec(struct radix_tree_node *node)
 {
+	VM_BUG_ON(!workingset_node_shadows(node));
 	node->count -= 1U << RADIX_TREE_COUNT_SHIFT;
 }

mm/filemap.c +43 ~~-43~~

104 lines not on this page · raw message

mm/workingset.c +4 -6

index aa017133744b..df66f426fdcf 100644
@@ -341,21 +341,19 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
 	 * no pages, so we expect to be able to remove them all and
 	 * delete and free the empty node afterwards.
 	 */
-
-	BUG_ON(!node->count);
-	BUG_ON(node->count & RADIX_TREE_COUNT_MASK);
+	BUG_ON(!workingset_node_shadows(node));
+	BUG_ON(workingset_node_pages(node));
 
 	for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
 		if (node->slots[i]) {
 			BUG_ON(!radix_tree_exceptional_entry(node->slots[i]));
 			node->slots[i] = NULL;
-			BUG_ON(node->count < (1U << RADIX_TREE_COUNT_SHIFT));
-			node->count -= 1U << RADIX_TREE_COUNT_SHIFT;
+			workingset_node_shadows_dec(node);
 			BUG_ON(!mapping->nrshadows);
 			mapping->nrshadows--;
 		}
 	}
-	BUG_ON(node->count);
+	BUG_ON(workingset_node_shadows(node));
 	inc_zone_state(page_zone(virt_to_page(node)), WORKINGSET_NODERECLAIM);
 	if (!__radix_tree_delete_node(&mapping->page_tree, node))
 		BUG();

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Johannes Weiner

2016-10-24 18:52 UTC #2 lore raw

Re: [Stable 4.4 - NEEDS REVIEW - 1/3] mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()

Quoted 69 lines · Michal Hocko

From: Johannes Weiner <[email protected]>
Commit 22f2ac51b6d643666f4db093f13144f773ff3f3a upstream.
Antonio reports the following crash when using fuse under memory pressure:
kernel BUG at /build/linux-a2WvEb/linux-4.4.0/mm/workingset.c:346! invalid opcode: 0000 [#1] SMP
  Modules linked in: all of them
  CPU: 2 PID: 63 Comm: kswapd0 Not tainted 4.4.0-36-generic #55-Ubuntu
  Hardware name: System manufacturer System Product Name/P8H67-M PRO, BIOS 3904 04/27/2013
  task: ffff88040cae6040 ti: ffff880407488000 task.ti: ffff880407488000
  RIP: shadow_lru_isolate+0x181/0x190
  Call Trace:
    __list_lru_walk_one.isra.3+0x8f/0x130
    list_lru_walk_one+0x23/0x30
    scan_shadow_nodes+0x34/0x50
    shrink_slab.part.40+0x1ed/0x3d0
    shrink_zone+0x2ca/0x2e0
    kswapd+0x51e/0x990
    kthread+0xd8/0xf0
    ret_from_fork+0x3f/0x70
which corresponds to the following sanity check in the shadow node tracking:
  BUG_ON(node->count & RADIX_TREE_COUNT_MASK);
The workingset code tracks radix tree nodes that exclusively contain shadow entries of evicted pages in them, and this (somewhat obscure) line checks whether there are real pages left that would interfere with reclaim of the radix tree node under memory pressure.
While discussing ways how fuse might sneak pages into the radix tree past the workingset code, Miklos pointed to replace_page_cache_page(), and indeed there is a problem there: it properly accounts for the old page being removed - __delete_from_page_cache() does that - but then does a raw raw radix_tree_insert(), not accounting for the replacement page. Eventually the page count bits in node->count underflow while leaving the node incorrectly linked to the shadow node LRU.
To address this, make sure replace_page_cache_page() uses the tracked page insertion code, page_cache_tree_insert(). This fixes the page accounting and makes sure page-containing nodes are properly unlinked from the shadow node LRU again.
Also, make the sanity checks a bit less obscure by using the helpers for checking the number of pages and shadows in a radix tree node.
Fixes 449dd6984d0e ("mm: keep page cache radix tree nodes in check")
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Johannes Weiner <[email protected]>
Reported-by Antonio SJ Musumeci <[email protected]>
Debugged-by Miklos Szeredi <[email protected]>
Cc <[email protected]> [3.15+]
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
Signed-off-by Michal Hocko <[email protected]>
---
 include/linux/swap.h |  2 ++
 mm/filemap.c         | 86 ++++++++++++++++++++++++++--------------------------
 mm/workingset.c      | 10 +++---
 3 files changed, 49 insertions(+), 49 deletions(-)
include/linux/swap.h +0 -0
index 7ba7dccaf0e7..b28de19aadbf 100644

include/linux/swap.h static inline void workingset_node_pages_inc(struct radix_tree_node *node) · line 271

Quoted 6 lines

include/linux/swap.h +1 -0

@@ -266,6 +266,7 @@ static inline void workingset_node_pages_inc(struct radix_tree_node *node)
 
 static inline void workingset_node_pages_dec(struct radix_tree_node *node)
 {
+	VM_BUG_ON(!workingset_node_pages(node));
 	node->count--;
 }

We should also pull 21f54ddae449 ("Using BUG_ON() as an assert() is _never_ acceptable") into stable on top of this patch to replace the BUG_ONs with warnings.

Otherwise this looks good to me.

Michal Hocko

author

2016-10-24 18:58 UTC #3 lore raw

Re: [Stable 4.4 - NEEDS REVIEW - 1/3] mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()

Quoted 1 line · Johannes Weiner

On Mon, Oct 24, 2016 at 05:26:03PM +0200, Michal Hocko wrote:

[...]

Quoted 16 lines

include/linux/swap.h static inline void workingset_node_pages_inc(struct radix_tree_node *node) · line 271
Quoted 11 lines
include/linux/swap.h +1 -0
index 7ba7dccaf0e7..b28de19aadbf 100644
@@ -266,6 +266,7 @@ static inline void workingset_node_pages_inc(struct radix_tree_node *node)
 
 static inline void workingset_node_pages_dec(struct radix_tree_node *node)
 {
+	VM_BUG_ON(!workingset_node_pages(node));
 	node->count--;
 }
We should also pull 21f54ddae449 ("Using BUG_ON() as an assert() is _never_ acceptable") into stable on top of this patch to replace the BUG_ONs with warnings.

Quoted 1 line

Otherwise this looks good to me.

OK, I have put that one on top and after the review will post it in one series. Thanks for the review Johannes!

Signature · 8 lines

Michal Hocko
SUSE Labs

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Michal Hocko

author

2016-10-24 15:26 UTC #4 lore raw

PATCH 2/3 mm: filemap: don't plant shadow entries without radix tree node

In reply to Michal Hocko

From: Johannes Weiner <[email protected]>

Commit d3798ae8c6f3767c726403c2ca6ecc317752c9dd upstream.

When the underflow checks were added to workingset_node_shadow_dec(), they triggered immediately:

kernel BUG at ./include/linux/swap.h:276!
invalid opcode: 0000 [#1] SMP

  Modules linked in: isofs usb_storage fuse xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_REJECT nf_reject_ipv6
   soundcore wmi acpi_als pinctrl_sunrisepoint kfifo_buf tpm_tis industrialio acpi_pad pinctrl_intel tpm_tis_core tpm nfsd auth_rpcgss nfs_acl lockd grace sunrpc dm_crypt
  CPU: 0 PID: 20929 Comm: blkid Not tainted 4.8.0-rc8-00087-gbe67d60ba944 #1
  Hardware name: System manufacturer System Product Name/Z170-K, BIOS 1803 05/06/2016
  task: ffff8faa93ecd940 task.stack: ffff8faa7f478000
  RIP: page_cache_tree_insert+0xf1/0x100
  Call Trace:
    __add_to_page_cache_locked+0x12e/0x270
    add_to_page_cache_lru+0x4e/0xe0
    mpage_readpages+0x112/0x1d0
    blkdev_readpages+0x1d/0x20
    __do_page_cache_readahead+0x1ad/0x290
    force_page_cache_readahead+0xaa/0x100
    page_cache_sync_readahead+0x3f/0x50
    generic_file_read_iter+0x5af/0x740
    blkdev_read_iter+0x35/0x40
    __vfs_read+0xe1/0x130
    vfs_read+0x96/0x130
    SyS_read+0x55/0xc0
    entry_SYSCALL_64_fastpath+0x13/0x8f
  Code: 03 00 48 8b 5d d8 65 48 33 1c 25 28 00 00 00 44 89 e8 75 19 48 83 c4 18 5b 41 5c 41 5d 41 5e 5d c3 0f 0b 41 bd ef ff ff ff eb d7 <0f> 0b e8 88 68 ef ff 0f 1f 84 00
  RIP  page_cache_tree_insert+0xf1/0x100

This is a long-standing bug in the way shadow entries are accounted in the radix tree nodes. The shrinker needs to know when radix tree nodes contain only shadow entries, no pages, so node->count is split in half to count shadows in the upper bits and pages in the lower bits.

Unfortunately, the radix tree implementation doesn't know of this and assumes all entries are in node->count. When there is a shadow entry directly in root->rnode and the tree is later extended, the radix tree implementation will copy that entry into the new node and and bump its node->count, i.e. increases the page count bits. Once the shadow gets removed and we subtract from the upper counter, node->count underflows and triggers the warning. Afterwards, without node->count reaching 0 again, the radix tree node is leaked.

Limit shadow entries to when we have actual radix tree nodes and can count them properly. That means we lose the ability to detect refaults from files that had only the first page faulted in at eviction time.

Fixes 449dd6984d0e ("mm: keep page cache radix tree nodes in check")

Signed-off-by Johannes Weiner <[email protected]>

Reported-and-tested-by Linus Torvalds <[email protected]>

Reviewed-by Jan Kara <[email protected]>

Cc Andrew Morton <[email protected]>

Cc [email protected]

Signed-off-by Linus Torvalds <[email protected]>

Signed-off-by Michal Hocko <[email protected]>

---
 include/linux/radix-tree.h |  3 +++
 lib/radix-tree.c           | 14 ++++++++++++++
 mm/filemap.c               | 48 +++++++++++++++++++++-------------------------
 3 files changed, 39 insertions(+), 26 deletions(-)

include/linux/radix-tree.h +3 -0

index 5d5174b59802..1fe61d2a3875 100644
@@ -271,6 +271,9 @@ bool __radix_tree_delete_node(struct radix_tree_root *root,
 			      struct radix_tree_node *node);
 void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
 void *radix_tree_delete(struct radix_tree_root *, unsigned long);
+void radix_tree_clear_tags(struct radix_tree_root *root,
+			   struct radix_tree_node *node,
+			   void **slot);
 unsigned int
 radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
 			unsigned long first_index, unsigned int max_items);

lib/radix-tree.c +14 -0

index 6b79e9026e24..3ca8be1d1c70 100644
@@ -1430,6 +1430,20 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 }
 EXPORT_SYMBOL(radix_tree_delete);
 
+void radix_tree_clear_tags(struct radix_tree_root *root,
+			   struct radix_tree_node *node,
+			   void **slot)
+{
+	if (node) {
+		unsigned int tag, offset = get_slot_offset(node, slot);
+		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
+			node_tag_clear(root, node, tag, offset);
+	} else {
+		/* Clear root node tags */
+		root->gfp_mask &= __GFP_BITS_MASK;
+	}
+}
+
 /**
  *	radix_tree_tagged - test whether any items in the tree are tagged
  *	@root:		radix tree root

mm/filemap.c +22 ~~-26~~

72 lines not on this page · raw message

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2.9.3

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Johannes Weiner

Reviewed-by Jan Kara on v1 2/3

2016-10-24 18:56 UTC #5 lore raw

Re: [Stable 4.4 - NEEDS REVIEW - 2/3] mm: filemap: don't plant shadow entries without radix tree node

Hi Michal,

Quoted 22 lines · Michal Hocko

(quoted diff) +0 ~~-12~~

@@ -155,44 +155,27 @@ static void page_cache_tree_delete(struct address_space *mapping,
 				   struct page *page, void *shadow)
 {
 	struct radix_tree_node *node;
-	unsigned long index;
-	unsigned int offset;
-	unsigned int tag;
 	void **slot;
 
 	VM_BUG_ON(!PageLocked(page));
 
 	__radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot);
 
-	if (shadow) {
-		mapping->nrshadows++;
-		/*
-		 * Make sure the nrshadows update is committed before
-		 * the nrpages update so that final truncate racing
-		 * with reclaim does not see both counters 0 at the
-		 * same time and miss a shadow entry.
-		 */
-		smp_wmb();

Review static void page_cache_tree_delete(struct address_space *mapping, · line 184

Quoted 10 lines

(quoted diff) +1 -7

-	}
-	mapping->nrpages--;
+	radix_tree_clear_tags(&mapping->page_tree, node, slot);
 
 	if (!node) {
-		/* Clear direct pointer tags in root node */
-		mapping->page_tree.gfp_mask &= __GFP_BITS_MASK;
-		radix_tree_replace_slot(slot, shadow);
-		return;
-	}

There is no need to include the refactoring of the tag clearing in the stable backport. I already sent a simpler backport of this patch for 4.4 to Greg, attached here for reference:

Quoted 1 line

From ba2dae8c4ddcc70a1d7bb1478f4c7c6ffe130b6f Mon Sep 17 00:00:00 2001

From: Johannes Weiner <[email protected]>
Date: Fri, 21 Oct 2016 13:40:41 -0400
Subject: [PATCH] mm: filemap: don't plant shadow entries without radix tree
node

commit d3798ae8c6f3767c726403c2ca6ecc317752c9dd upstream.

When the underflow checks were added to workingset_node_shadow_dec(), they triggered immediately:

kernel BUG at ./include/linux/swap.h:276!
invalid opcode: 0000 [#1] SMP

  Modules linked in: isofs usb_storage fuse xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 tun nf_conntrack_netbios_ns nf_conntrack_broadcast ip6t_REJECT nf_reject_ipv6
   soundcore wmi acpi_als pinctrl_sunrisepoint kfifo_buf tpm_tis industrialio acpi_pad pinctrl_intel tpm_tis_core tpm nfsd auth_rpcgss nfs_acl lockd grace sunrpc dm_crypt
  CPU: 0 PID: 20929 Comm: blkid Not tainted 4.8.0-rc8-00087-gbe67d60ba944 #1
  Hardware name: System manufacturer System Product Name/Z170-K, BIOS 1803 05/06/2016
  task: ffff8faa93ecd940 task.stack: ffff8faa7f478000
  RIP: page_cache_tree_insert+0xf1/0x100
  Call Trace:
    __add_to_page_cache_locked+0x12e/0x270
    add_to_page_cache_lru+0x4e/0xe0
    mpage_readpages+0x112/0x1d0
    blkdev_readpages+0x1d/0x20
    __do_page_cache_readahead+0x1ad/0x290
    force_page_cache_readahead+0xaa/0x100
    page_cache_sync_readahead+0x3f/0x50
    generic_file_read_iter+0x5af/0x740
    blkdev_read_iter+0x35/0x40
    __vfs_read+0xe1/0x130
    vfs_read+0x96/0x130
    SyS_read+0x55/0xc0
    entry_SYSCALL_64_fastpath+0x13/0x8f
  Code: 03 00 48 8b 5d d8 65 48 33 1c 25 28 00 00 00 44 89 e8 75 19 48 83 c4 18 5b 41 5c 41 5d 41 5e 5d c3 0f 0b 41 bd ef ff ff ff eb d7 <0f> 0b e8 88 68 ef ff 0f 1f 84 00
  RIP  page_cache_tree_insert+0xf1/0x100

Fixes 449dd6984d0e ("mm: keep page cache radix tree nodes in check")

Signed-off-by Johannes Weiner <[email protected]>

Reported-and-tested-by Linus Torvalds <[email protected]>

Reviewed-by Jan Kara <[email protected]>

Cc Andrew Morton <[email protected]>

Signed-off-by Linus Torvalds <[email protected]>

---
 mm/filemap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

mm/filemap.c +8 -0

index 1bb007624b53..fb52502d12f4 100644
@@ -122,6 +122,14 @@ static void page_cache_tree_delete(struct address_space *mapping,
 
 	__radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot);
 
+	if (!node) {
+		/*
+		 * We need a node to properly account shadow
+		 * entries. Don't plant any without. XXX
+		 */
+		shadow = NULL;
+	}
+
 	if (shadow) {
 		mapping->nrshadows++;
 		/*

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Michal Hocko

author

2016-10-24 19:08 UTC #6 lore raw

Re: [Stable 4.4 - NEEDS REVIEW - 2/3] mm: filemap: don't plant shadow entries without radix tree node

Quoted 29 lines · Johannes Weiner

Hi Michal,

Quoted 26 lines · Michal Hocko

(quoted diff) +1 ~~-14~~

@@ -155,44 +155,27 @@ static void page_cache_tree_delete(struct address_space *mapping,
 				   struct page *page, void *shadow)
 {
 	struct radix_tree_node *node;
-	unsigned long index;
-	unsigned int offset;
-	unsigned int tag;
 	void **slot;
 
 	VM_BUG_ON(!PageLocked(page));
 
 	__radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot);
 
-	if (shadow) {
-		mapping->nrshadows++;
-		/*
-		 * Make sure the nrshadows update is committed before
-		 * the nrpages update so that final truncate racing
-		 * with reclaim does not see both counters 0 at the
-		 * same time and miss a shadow entry.
-		 */
-		smp_wmb();
-	}
-	mapping->nrpages--;
+	radix_tree_clear_tags(&mapping->page_tree, node, slot);

Quoted 10 lines

Review static void page_cache_tree_delete(struct address_space *mapping, · line 184
Quoted 6 lines
(quoted diff) +0 -5
 	if (!node) {
-		/* Clear direct pointer tags in root node */
-		mapping->page_tree.gfp_mask &= __GFP_BITS_MASK;
-		radix_tree_replace_slot(slot, shadow);
-		return;
-	}
There is no need to include the refactoring of the tag clearing in the stable backport. I already sent a simpler backport of this patch for 4.4 to Greg, attached here for reference:

I do not see this in 4.4 so maybe it's fallen through cracks. Yours definitely looks easier and I will use it. I will post all 4 patches for inclusion for stable tomorrow unless something else pops out.

Thanks for the review again!

Signature · 8 lines

Michal Hocko
SUSE Labs

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Michal Hocko

author

2016-10-24 15:26 UTC #7 lore raw

PATCH 3/3 mm: filemap: fix mapping->nrpages double accounting in fuse

In reply to Michal Hocko

From: Johannes Weiner <[email protected]>

Commit 3ddf40e8c31964b744ff10abb48c8e36a83ec6e7 upstream.

Commit 22f2ac51b6d6 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()") switched replace_page_cache() from raw radix tree operations to page_cache_tree_insert() but didn't take into account that the latter function, unlike the raw radix tree op, handles mapping->nrpages. As a result, that counter is bumped for each page replacement rather than balanced out even.

The mapping->nrpages counter is used to skip needless radix tree walks when invalidating, truncating, syncing inodes without pages, as well as statistics for userspace. Since the error is positive, we'll do more page cache tree walks than necessary; we won't miss a necessary one. And we'll report more buffer pages to userspace than there are. The error is limited to fuse inodes.

Fixes 22f2ac51b6d6 ("mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()")

Signed-off-by Johannes Weiner <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Miklos Szeredi <[email protected]>

Cc [email protected]

Signed-off-by Linus Torvalds <[email protected]>

Signed-off-by Michal Hocko <[email protected]>

---
 mm/filemap.c | 1 -
 1 file changed, 1 deletion(-)

mm/filemap.c +0 -1

index c9c19c12f61d..8675ce8a8f87 100644
@@ -578,7 +578,6 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 		__delete_from_page_cache(old, NULL, memcg);
 		error = page_cache_tree_insert(mapping, new, NULL);
 		BUG_ON(error);
-		mapping->nrpages++;
 
 		/*
 		 * hugetlb pages do not participate in page cache accounting.

Signature · 7 lines

2.9.3

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Johannes Weiner

2016-10-24 18:56 UTC #8 lore raw

Re: [Stable 4.4 - NEEDS REVIEW - 3/3] mm: filemap: fix mapping->nrpages double accounting in fuse

This one looks good to me.

Thanks