From 032f8e04c0353f015d243008f039bb6e18a173c7 Mon Sep 17 00:00:00 2001 From: Waiman Long Date: Thu, 4 Feb 2021 18:32:45 -0800 Subject: [PATCH] mm/filemap: add missing mem_cgroup_uncharge() to __add_to_page_cache_locked() 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 Reviewed-by: Alex Shi Acked-by: Johannes Weiner Cc: Matthew Wilcox Cc: Miaohe Lin Cc: Muchun Song Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/filemap.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index 0b2067b3c328..125b69f59caa 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -835,6 +835,7 @@ noinline int __add_to_page_cache_locked(struct page *page, 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(struct page *page, error = mem_cgroup_charge(page, current->mm, gfp); if (error) goto error; + charged = true; } gfp &= GFP_RECLAIM_MASK; @@ -896,6 +898,8 @@ noinline int __add_to_page_cache_locked(struct page *page, if (xas_error(&xas)) { error = xas_error(&xas); + if (charged) + mem_cgroup_uncharge(page); goto error; }