linux-stable.git/mm/filemap.c, branch v5.10.78

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

2021-02-10T08:29:21+00:00

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

revert "mm/filemap: add static for function __add_to_page_cache_locked"

2020-12-11T22:02:14+00:00

Revert commit 3351b16af494 ("mm/filemap: add static for function
__add_to_page_cache_locked") due to incompatibility with
ALLOW_ERROR_INJECTION which result in build errors.

Link: https://lkml.kernel.org/r/CAADnVQJ6tmzBXvtroBuEH6QA0H+q7yaSKxrVvVxhqr3KBZdEXg@mail.gmail.com
Tested-by: Justin Forbes 
Tested-by: Greg Thelen 
Acked-by: Alexei Starovoitov 
Cc: Michal Kubecek 
Cc: Alex Shi 
Cc: Souptick Joarder 
Cc: Daniel Borkmann 
Cc: Josef Bacik 
Cc: Tony Luck 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/filemap: add static for function __add_to_page_cache_locked

2020-12-06T18:19:07+00:00

  mm/filemap.c:830:14: warning: no previous prototype for `__add_to_page_cache_locked' [-Wmissing-prototypes]

Signed-off-by: Alex Shi 
Signed-off-by: Andrew Morton 
Cc: Souptick Joarder 
Link: https://lkml.kernel.org/r/1604661895-5495-1-git-send-email-alex.shi@linux.alibaba.com
Signed-off-by: Linus Torvalds

mm: fix VM_BUG_ON(PageTail) and BUG_ON(PageWriteback)

2020-11-24T23:23:19+00:00

Twice now, when exercising ext4 looped on shmem huge pages, I have crashed
on the PF_ONLY_HEAD check inside PageWaiters(): ext4_finish_bio() calling
end_page_writeback() calling wake_up_page() on tail of a shmem huge page,
no longer an ext4 page at all.

The problem is that PageWriteback is not accompanied by a page reference
(as the NOTE at the end of test_clear_page_writeback() acknowledges): as
soon as TestClearPageWriteback has been done, that page could be removed
from page cache, freed, and reused for something else by the time that
wake_up_page() is reached.

https://lore.kernel.org/linux-mm/20200827122019.GC14765@casper.infradead.org/
Matthew Wilcox suggested avoiding or weakening the PageWaiters() tail
check; but I'm paranoid about even looking at an unreferenced struct page,
lest its memory might itself have already been reused or hotremoved (and
wake_up_page_bit() may modify that memory with its ClearPageWaiters()).

Then on crashing a second time, realized there's a stronger reason against
that approach.  If my testing just occasionally crashes on that check,
when the page is reused for part of a compound page, wouldn't it be much
more common for the page to get reused as an order-0 page before reaching
wake_up_page()?  And on rare occasions, might that reused page already be
marked PageWriteback by its new user, and already be waited upon?  What
would that look like?

It would look like BUG_ON(PageWriteback) after wait_on_page_writeback()
in write_cache_pages() (though I have never seen that crash myself).

Matthew Wilcox explaining this to himself:
 "page is allocated, added to page cache, dirtied, writeback starts,

  --- thread A ---
  filesystem calls end_page_writeback()
        test_clear_page_writeback()
  --- context switch to thread B ---
  truncate_inode_pages_range() finds the page, it doesn't have writeback set,
  we delete it from the page cache.  Page gets reallocated, dirtied, writeback
  starts again.  Then we call write_cache_pages(), see
  PageWriteback() set, call wait_on_page_writeback()
  --- context switch back to thread A ---
  wake_up_page(page, PG_writeback);
  ... thread B is woken, but because the wakeup was for the old use of
  the page, PageWriteback is still set.

  Devious"

And prior to 2a9127fcf229 ("mm: rewrite wait_on_page_bit_common() logic")
this would have been much less likely: before that, wake_page_function()'s
non-exclusive case would stop walking and not wake if it found Writeback
already set again; whereas now the non-exclusive case proceeds to wake.

I have not thought of a fix that does not add a little overhead: the
simplest fix is for end_page_writeback() to get_page() before calling
test_clear_page_writeback(), then put_page() after wake_up_page().

Was there a chance of missed wakeups before, since a page freed before
reaching wake_up_page() would have PageWaiters cleared?  I think not,
because each waiter does hold a reference on the page.  This bug comes
when the old use of the page, the one we do TestClearPageWriteback on,
had *no* waiters, so no additional page reference beyond the page cache
(and whoever racily freed it).  The reuse of the page has a waiter
holding a reference, and its own PageWriteback set; but the belated
wake_up_page() has woken the reuse to hit that BUG_ON(PageWriteback).

Reported-by: syzbot+3622cea378100f45d59f@syzkaller.appspotmail.com
Reported-by: Qian Cai 
Fixes: 2a9127fcf229 ("mm: rewrite wait_on_page_bit_common() logic")
Signed-off-by: Hugh Dickins 
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Linus Torvalds

mm: never attempt async page lock if we've transferred data already

2020-11-16T20:39:34+00:00

We catch the case where we enter generic_file_buffered_read() with data
already transferred, but we also need to be careful not to allow an async
page lock if we're looping transferring data. If not, we could be
returning -EIOCBQUEUED instead of the transferred amount, and it could
result in double waitqueue additions as well.

Cc: stable@vger.kernel.org # v5.9
Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()")
Signed-off-by: Jens Axboe

Merge tag 'vfs-5.10-merge-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

2020-10-23T18:33:41+00:00

Pull clone/dedupe/remap code refactoring from Darrick Wong:
 "Move the generic file range remap (aka reflink and dedupe) functions
  out of mm/filemap.c and fs/read_write.c and into fs/remap_range.c to
  reduce clutter in the first two files"

* tag 'vfs-5.10-merge-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  vfs: move the generic write and copy checks out of mm
  vfs: move the remap range helpers to remap_range.c
  vfs: move generic_remap_checks out of mm

mm: mark async iocb read as NOWAIT once some data has been copied

2020-10-17T19:49:05+00:00

Once we've copied some data for an iocb that is marked with IOCB_WAITQ,
we should no longer attempt to async lock a new page. Instead make sure
we return the copied amount, and let the caller retry, instead of
returning -EIOCBQUEUED for a new page.

This should only be possible with read-ahead disabled on the below
device, and multiple threads racing on the same file. Haven't been able
to reproduce on anything else.

Cc: stable@vger.kernel.org # v5.9
Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()")
Reported-by: Kent Overstreet 
Signed-off-by: Jens Axboe

Merge branch 'akpm' (patches from Andrew)

2020-10-16T18:31:55+00:00

Merge more updates from Andrew Morton:
 "155 patches.

  Subsystems affected by this patch series: mm (dax, debug, thp,
  readahead, page-poison, util, memory-hotplug, zram, cleanups), misc,
  core-kernel, get_maintainer, MAINTAINERS, lib, bitops, checkpatch,
  binfmt, ramfs, autofs, nilfs, rapidio, panic, relay, kgdb, ubsan,
  romfs, and fault-injection"

* emailed patches from Andrew Morton : (155 commits)
  lib, uaccess: add failure injection to usercopy functions
  lib, include/linux: add usercopy failure capability
  ROMFS: support inode blocks calculation
  ubsan: introduce CONFIG_UBSAN_LOCAL_BOUNDS for Clang
  sched.h: drop in_ubsan field when UBSAN is in trap mode
  scripts/gdb/tasks: add headers and improve spacing format
  scripts/gdb/proc: add struct mount & struct super_block addr in lx-mounts command
  kernel/relay.c: drop unneeded initialization
  panic: dump registers on panic_on_warn
  rapidio: fix the missed put_device() for rio_mport_add_riodev
  rapidio: fix error handling path
  nilfs2: fix some kernel-doc warnings for nilfs2
  autofs: harden ioctl table
  ramfs: fix nommu mmap with gaps in the page cache
  mm: remove the now-unnecessary mmget_still_valid() hack
  mm/gup: take mmap_lock in get_dump_page()
  binfmt_elf, binfmt_elf_fdpic: use a VMA list snapshot
  coredump: rework elf/elf_fdpic vma_dump_size() into common helper
  coredump: refactor page range dumping into common helper
  coredump: let dump_emit() bail out on short writes
  ...

mm: fix some broken comments

2020-10-16T18:11:19+00:00

Fix some broken comments including typo, grammar error and wrong function
name.

Signed-off-by: Miaohe Lin 
Signed-off-by: Andrew Morton 
Link: https://lkml.kernel.org/r/20200913095456.54873-1-linmiaohe@huawei.com
Signed-off-by: Linus Torvalds

mm/filemap: fold ra_submit into do_sync_mmap_readahead

2020-10-16T18:11:16+00:00

Fold ra_submit() into its last remaining user and pass the
readahead_control struct to both do_page_cache_ra() and
page_cache_sync_ra().

Signed-off-by: David Howells 
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Cc: Eric Biggers 
Link: https://lkml.kernel.org/r/20200903140844.14194-9-willy@infradead.org
Signed-off-by: Linus Torvalds