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Message-Id: <20210208145822.572875718@linuxfoundation.org>
Date: Mon, 8 Feb 2021 16:01:32 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Waiman Long <longman@...hat.com>,
Alex Shi <alex.shi@...ux.alibaba.com>,
Johannes Weiner <hannes@...xchg.org>,
Matthew Wilcox <willy@...radead.org>,
Miaohe Lin <linmiaohe@...wei.com>,
Muchun Song <smuchun@...il.com>,
Michal Hocko <mhocko@...e.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.10 105/120] mm/filemap: add missing mem_cgroup_uncharge() to __add_to_page_cache_locked()
From: Waiman Long <longman@...hat.com>
commit da74240eb3fcd806edb1643874363e954d9e948b upstream.
Commit 3fea5a499d57 ("mm: memcontrol: convert page cache to a new
mem_cgroup_charge() API") introduced a bug in __add_to_page_cache_locked()
causing the following splat:
page dumped because: VM_BUG_ON_PAGE(page_memcg(page))
pages's memcg:ffff8889a4116000
------------[ cut here ]------------
kernel BUG at mm/memcontrol.c:2924!
invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 35 PID: 12345 Comm: cat Tainted: G S W I 5.11.0-rc4-debug+ #1
Hardware name: HP HP Z8 G4 Workstation/81C7, BIOS P60 v01.25 12/06/2017
RIP: commit_charge+0xf4/0x130
Call Trace:
mem_cgroup_charge+0x175/0x770
__add_to_page_cache_locked+0x712/0xad0
add_to_page_cache_lru+0xc5/0x1f0
cachefiles_read_or_alloc_pages+0x895/0x2e10 [cachefiles]
__fscache_read_or_alloc_pages+0x6c0/0xa00 [fscache]
__nfs_readpages_from_fscache+0x16d/0x630 [nfs]
nfs_readpages+0x24e/0x540 [nfs]
read_pages+0x5b1/0xc40
page_cache_ra_unbounded+0x460/0x750
generic_file_buffered_read_get_pages+0x290/0x1710
generic_file_buffered_read+0x2a9/0xc30
nfs_file_read+0x13f/0x230 [nfs]
new_sync_read+0x3af/0x610
vfs_read+0x339/0x4b0
ksys_read+0xf1/0x1c0
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Before that commit, there was a try_charge() and commit_charge() in
__add_to_page_cache_locked(). These two separated charge functions were
replaced by a single mem_cgroup_charge(). However, it forgot to add a
matching mem_cgroup_uncharge() when the xarray insertion failed with the
page released back to the pool.
Fix this by adding a mem_cgroup_uncharge() call when insertion error
happens.
Link: https://lkml.kernel.org/r/20210125042441.20030-1-longman@redhat.com
Fixes: 3fea5a499d57 ("mm: memcontrol: convert page cache to a new mem_cgroup_charge() API")
Signed-off-by: Waiman Long <longman@...hat.com>
Reviewed-by: Alex Shi <alex.shi@...ux.alibaba.com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Miaohe Lin <linmiaohe@...wei.com>
Cc: Muchun Song <smuchun@...il.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
mm/filemap.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -835,6 +835,7 @@ noinline int __add_to_page_cache_locked(
XA_STATE(xas, &mapping->i_pages, offset);
int huge = PageHuge(page);
int error;
+ bool charged = false;
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapBacked(page), page);
@@ -848,6 +849,7 @@ noinline int __add_to_page_cache_locked(
error = mem_cgroup_charge(page, current->mm, gfp);
if (error)
goto error;
+ charged = true;
}
gfp &= GFP_RECLAIM_MASK;
@@ -896,6 +898,8 @@ unlock:
if (xas_error(&xas)) {
error = xas_error(&xas);
+ if (charged)
+ mem_cgroup_uncharge(page);
goto error;
}
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