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mm/filemap: add missing mem_cgroup_uncharge() to __add_to_page_cache_locked()

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Commit 3fea5a499d ("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: 3fea5a499d ("mm: memcontrol: convert page cache to a new mem_cgroup_charge() API")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <smuchun@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Waiman Long 2021-02-04 18:32:45 -08:00 committed by Linus Torvalds
parent 9c41e526a5
commit da74240eb3
1 changed files with 4 additions and 0 deletions
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4
mm/filemap.c
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@ -835,6 +835,7 @@ noinline int __add_to_page_cache_locked(struct page *page,
XA_STATE(xas, &mapping->i_pages, offset); XA_STATE(xas, &mapping->i_pages, offset);
int huge = PageHuge(page); int huge = PageHuge(page);
int error; int error;
bool charged = false;
VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapBacked(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); error = mem_cgroup_charge(page, current->mm, gfp);
if (error) if (error)
goto error; goto error;
charged = true;
} }
gfp &= GFP_RECLAIM_MASK; gfp &= GFP_RECLAIM_MASK;
@ -896,6 +898,8 @@ unlock:
if (xas_error(&xas)) { if (xas_error(&xas)) {
error = xas_error(&xas); error = xas_error(&xas);
if (charged)
mem_cgroup_uncharge(page);
goto error; goto error;
} }