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Patch series "migrate_pages: fix deadlock in batched synchronous
migration", v2.
Two deadlock bugs were reported for the migrate_pages() batching series.
Thanks Hugh and Pengfei. Analysis shows that if we have locked some other
folios except the one we are migrating, it's not safe in general to wait
synchronously, for example, to wait the writeback to complete or wait to
lock the buffer head.
So 1/3 fixes the deadlock in a simple way, where the batching support for
the synchronous migration is disabled. The change is straightforward and
easy to be understood. While 3/3 re-introduce the batching for
synchronous migration via trying to migrate asynchronously in batch
optimistically, then fall back to migrate synchronously one by one for
fail-to-migrate folios. Test shows that this can restore the TLB flushing
batching performance for synchronous migration effectively.
This patch (of 3):
Two deadlock bugs were reported for the migrate_pages() batching series.
Thanks Hugh and Pengfei! For example, in the following deadlock trace
snippet,
INFO: task kworker/u4:0:9 blocked for more than 147 seconds.
Not tainted 6.2.0-rc4-kvm+ #1314
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:0 state:D stack:0 pid:9 ppid:2 flags:0x00004000
Workqueue: loop4 loop_rootcg_workfn
Call Trace:
<TASK>
__schedule+0x43b/0xd00
schedule+0x6a/0xf0
io_schedule+0x4a/0x80
folio_wait_bit_common+0x1b5/0x4e0
? __pfx_wake_page_function+0x10/0x10
__filemap_get_folio+0x73d/0x770
shmem_get_folio_gfp+0x1fd/0xc80
shmem_write_begin+0x91/0x220
generic_perform_write+0x10e/0x2e0
__generic_file_write_iter+0x17e/0x290
? generic_write_checks+0x12b/0x1a0
generic_file_write_iter+0x97/0x180
? __sanitizer_cov_trace_const_cmp4+0x1a/0x20
do_iter_readv_writev+0x13c/0x210
? __sanitizer_cov_trace_const_cmp4+0x1a/0x20
do_iter_write+0xf6/0x330
vfs_iter_write+0x46/0x70
loop_process_work+0x723/0xfe0
loop_rootcg_workfn+0x28/0x40
process_one_work+0x3cc/0x8d0
worker_thread+0x66/0x630
? __pfx_worker_thread+0x10/0x10
kthread+0x153/0x190
? __pfx_kthread+0x10/0x10
ret_from_fork+0x29/0x50
</TASK>
INFO: task repro:1023 blocked for more than 147 seconds.
Not tainted 6.2.0-rc4-kvm+ #1314
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:repro state:D stack:0 pid:1023 ppid:360 flags:0x00004004
Call Trace:
<TASK>
__schedule+0x43b/0xd00
schedule+0x6a/0xf0
io_schedule+0x4a/0x80
folio_wait_bit_common+0x1b5/0x4e0
? compaction_alloc+0x77/0x1150
? __pfx_wake_page_function+0x10/0x10
folio_wait_bit+0x30/0x40
folio_wait_writeback+0x2e/0x1e0
migrate_pages_batch+0x555/0x1ac0
? __pfx_compaction_alloc+0x10/0x10
? __pfx_compaction_free+0x10/0x10
? __this_cpu_preempt_check+0x17/0x20
? lock_is_held_type+0xe6/0x140
migrate_pages+0x100e/0x1180
? __pfx_compaction_free+0x10/0x10
? __pfx_compaction_alloc+0x10/0x10
compact_zone+0xe10/0x1b50
? lock_is_held_type+0xe6/0x140
? check_preemption_disabled+0x80/0xf0
compact_node+0xa3/0x100
? __sanitizer_cov_trace_const_cmp8+0x1c/0x30
? _find_first_bit+0x7b/0x90
sysctl_compaction_handler+0x5d/0xb0
proc_sys_call_handler+0x29d/0x420
proc_sys_write+0x2b/0x40
vfs_write+0x3a3/0x780
ksys_write+0xb7/0x180
__x64_sys_write+0x26/0x30
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7f3a2471f59d
RSP: 002b:00007ffe567f7288 EFLAGS: 00000217 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3a2471f59d
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007ffe567f72a0 R08: 0000000000000010 R09: 0000000000000010
R10: 0000000000000010 R11: 0000000000000217 R12: 00000000004012e0
R13: 00007ffe567f73e0 R14: 0000000000000000 R15: 0000000000000000
</TASK>
The page migration task has held the lock of the shmem folio A, and is
waiting the writeback of the folio B of the file system on the loop block
device to complete. While the loop worker task which writes back the
folio B is waiting to lock the shmem folio A, because the folio A backs
the folio B in the loop device. Thus deadlock is triggered.
In general, if we have locked some other folios except the one we are
migrating, it's not safe to wait synchronously, for example, to wait the
writeback to complete or wait to lock the buffer head.
To fix the deadlock, in this patch, we avoid to batch the page migration
except for MIGRATE_ASYNC mode. In MIGRATE_ASYNC mode, synchronous waiting
is avoided.
The fix can be improved further. We will do that as soon as possible.
Link: https://lkml.kernel.org/r/20230303030155.160983-1-ying.huang@intel.com
Link: https://lore.kernel.org/linux-mm/87a6c8c-c5c1-67dc-1e32-eb30831d6e3d@google.com/
Link: https://lore.kernel.org/linux-mm/874jrg7kke.fsf@yhuang6-desk2.ccr.corp.intel.com/
Link: https://lore.kernel.org/linux-mm/20230227110614.dngdub2j3exr6dfp@quack3/
Link: https://lkml.kernel.org/r/20230303030155.160983-2-ying.huang@intel.com
Fixes: 5dfab109d5 ("migrate_pages: batch _unmap and _move")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reported-by: Hugh Dickins <hughd@google.com>
Reported-by: "Xu, Pengfei" <pengfei.xu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Stefan Roesch <shr@devkernel.io>
Cc: Tejun Heo <tj@kernel.org>
Cc: Xin Hao <xhao@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The migration code ends up temporarily stashing information of the wrong
type in unused fields of the newly allocated destination folio. That
all works fine, but gcc does complain about the pointer type mis-use:
mm/migrate.c: In function ‘__migrate_folio_extract’:
mm/migrate.c:1050:20: note: randstruct: casting between randomized structure pointer types (ssa): ‘struct anon_vma’ and ‘struct address_space’
1050 | *anon_vmap = (void *)dst->mapping;
| ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
and gcc is actually right to complain since it really doesn't understand
that this is a very temporary special case where this is ok.
This could be fixed in different ways by just obfuscating the assignment
sufficiently that gcc doesn't see what is going on, but the truly
"proper C" way to do this is by explicitly using a union.
Using unions for type conversions like this is normally hugely ugly and
syntactically nasty, but this really is one of the few cases where we
want to make it clear that we're not doing type conversion, we're really
re-using the value bit-for-bit just using another type.
IOW, this should not become a common pattern, but in this one case using
that odd union is probably the best way to document to the compiler what
is conceptually going on here.
[ Side note: there are valid cases where we convert pointers to other
pointer types, notably the whole "folio vs page" situation, where the
types actually have fundamental commonalities.
The fact that the gcc note is limited to just randomized structures
means that we don't see equivalent warnings for those cases, but it
migth also mean that we miss other cases where we do play these kinds
of dodgy games, and this kind of explicit conversion might be a good
idea. ]
I verified that at least for an allmodconfig build on x86-64, this
generates the exact same code, apart from line numbers and assembler
comment changes.
Fixes: 64c8902ed4 ("migrate_pages: split unmap_and_move() to _unmap() and _move()")
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull MM updates from Andrew Morton:
- Daniel Verkamp has contributed a memfd series ("mm/memfd: add
F_SEAL_EXEC") which permits the setting of the memfd execute bit at
memfd creation time, with the option of sealing the state of the X
bit.
- Peter Xu adds a patch series ("mm/hugetlb: Make huge_pte_offset()
thread-safe for pmd unshare") which addresses a rare race condition
related to PMD unsharing.
- Several folioification patch serieses from Matthew Wilcox, Vishal
Moola, Sidhartha Kumar and Lorenzo Stoakes
- Johannes Weiner has a series ("mm: push down lock_page_memcg()")
which does perform some memcg maintenance and cleanup work.
- SeongJae Park has added DAMOS filtering to DAMON, with the series
"mm/damon/core: implement damos filter".
These filters provide users with finer-grained control over DAMOS's
actions. SeongJae has also done some DAMON cleanup work.
- Kairui Song adds a series ("Clean up and fixes for swap").
- Vernon Yang contributed the series "Clean up and refinement for maple
tree".
- Yu Zhao has contributed the "mm: multi-gen LRU: memcg LRU" series. It
adds to MGLRU an LRU of memcgs, to improve the scalability of global
reclaim.
- David Hildenbrand has added some userfaultfd cleanup work in the
series "mm: uffd-wp + change_protection() cleanups".
- Christoph Hellwig has removed the generic_writepages() library
function in the series "remove generic_writepages".
- Baolin Wang has performed some maintenance on the compaction code in
his series "Some small improvements for compaction".
- Sidhartha Kumar is doing some maintenance work on struct page in his
series "Get rid of tail page fields".
- David Hildenbrand contributed some cleanup, bugfixing and
generalization of pte management and of pte debugging in his series
"mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures with
swap PTEs".
- Mel Gorman and Neil Brown have removed the __GFP_ATOMIC allocation
flag in the series "Discard __GFP_ATOMIC".
- Sergey Senozhatsky has improved zsmalloc's memory utilization with
his series "zsmalloc: make zspage chain size configurable".
- Joey Gouly has added prctl() support for prohibiting the creation of
writeable+executable mappings.
The previous BPF-based approach had shortcomings. See "mm: In-kernel
support for memory-deny-write-execute (MDWE)".
- Waiman Long did some kmemleak cleanup and bugfixing in the series
"mm/kmemleak: Simplify kmemleak_cond_resched() & fix UAF".
- T.J. Alumbaugh has contributed some MGLRU cleanup work in his series
"mm: multi-gen LRU: improve".
- Jiaqi Yan has provided some enhancements to our memory error
statistics reporting, mainly by presenting the statistics on a
per-node basis. See the series "Introduce per NUMA node memory error
statistics".
- Mel Gorman has a second and hopefully final shot at fixing a CPU-hog
regression in compaction via his series "Fix excessive CPU usage
during compaction".
- Christoph Hellwig does some vmalloc maintenance work in the series
"cleanup vfree and vunmap".
- Christoph Hellwig has removed block_device_operations.rw_page() in
ths series "remove ->rw_page".
- We get some maple_tree improvements and cleanups in Liam Howlett's
series "VMA tree type safety and remove __vma_adjust()".
- Suren Baghdasaryan has done some work on the maintainability of our
vm_flags handling in the series "introduce vm_flags modifier
functions".
- Some pagemap cleanup and generalization work in Mike Rapoport's
series "mm, arch: add generic implementation of pfn_valid() for
FLATMEM" and "fixups for generic implementation of pfn_valid()"
- Baoquan He has done some work to make /proc/vmallocinfo and
/proc/kcore better represent the real state of things in his series
"mm/vmalloc.c: allow vread() to read out vm_map_ram areas".
- Jason Gunthorpe rationalized the GUP system's interface to the rest
of the kernel in the series "Simplify the external interface for
GUP".
- SeongJae Park wishes to migrate people from DAMON's debugfs interface
over to its sysfs interface. To support this, we'll temporarily be
printing warnings when people use the debugfs interface. See the
series "mm/damon: deprecate DAMON debugfs interface".
- Andrey Konovalov provided the accurately named "lib/stackdepot: fixes
and clean-ups" series.
- Huang Ying has provided a dramatic reduction in migration's TLB flush
IPI rates with the series "migrate_pages(): batch TLB flushing".
- Arnd Bergmann has some objtool fixups in "objtool warning fixes".
* tag 'mm-stable-2023-02-20-13-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (505 commits)
include/linux/migrate.h: remove unneeded externs
mm/memory_hotplug: cleanup return value handing in do_migrate_range()
mm/uffd: fix comment in handling pte markers
mm: change to return bool for isolate_movable_page()
mm: hugetlb: change to return bool for isolate_hugetlb()
mm: change to return bool for isolate_lru_page()
mm: change to return bool for folio_isolate_lru()
objtool: add UACCESS exceptions for __tsan_volatile_read/write
kmsan: disable ftrace in kmsan core code
kasan: mark addr_has_metadata __always_inline
mm: memcontrol: rename memcg_kmem_enabled()
sh: initialize max_mapnr
m68k/nommu: add missing definition of ARCH_PFN_OFFSET
mm: percpu: fix incorrect size in pcpu_obj_full_size()
maple_tree: reduce stack usage with gcc-9 and earlier
mm: page_alloc: call panic() when memoryless node allocation fails
mm: multi-gen LRU: avoid futile retries
migrate_pages: move THP/hugetlb migration support check to simplify code
migrate_pages: batch flushing TLB
migrate_pages: share more code between _unmap and _move
...
The TLB flushing will cost quite some CPU cycles during the folio
migration in some situations. For example, when migrate a folio of a
process with multiple active threads that run on multiple CPUs. After
batching the _unmap and _move in migrate_pages(), the TLB flushing can be
batched easily with the existing TLB flush batching mechanism. This patch
implements that.
We use the following test case to test the patch.
On a 2-socket Intel server,
- Run pmbench memory accessing benchmark
- Run `migratepages` to migrate pages of pmbench between node 0 and
node 1 back and forth.
With the patch, the TLB flushing IPI reduces 99.1% during the test and the
number of pages migrated successfully per second increases 291.7%.
Haoxin helped to test the patchset on an ARM64 server with 128 cores, 2
NUMA nodes. Test results show that the page migration performance
increases up to 78%.
NOTE: TLB flushing is batched only for normal folios, not for THP folios.
Because the overhead of TLB flushing for THP folios is much lower than
that for normal folios (about 1/512 on x86 platform).
Link: https://lkml.kernel.org/r/20230213123444.155149-9-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Bharata B Rao <bharata@amd.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "migrate_pages(): batch TLB flushing", v5.
Now, migrate_pages() migrates folios one by one, like the fake code as
follows,
for each folio
unmap
flush TLB
copy
restore map
If multiple folios are passed to migrate_pages(), there are opportunities
to batch the TLB flushing and copying. That is, we can change the code to
something as follows,
for each folio
unmap
for each folio
flush TLB
for each folio
copy
for each folio
restore map
The total number of TLB flushing IPI can be reduced considerably. And we
may use some hardware accelerator such as DSA to accelerate the folio
copying.
So in this patch, we refactor the migrate_pages() implementation and
implement the TLB flushing batching. Base on this, hardware accelerated
folio copying can be implemented.
If too many folios are passed to migrate_pages(), in the naive batched
implementation, we may unmap too many folios at the same time. The
possibility for a task to wait for the migrated folios to be mapped again
increases. So the latency may be hurt. To deal with this issue, the max
number of folios be unmapped in batch is restricted to no more than
HPAGE_PMD_NR in the unit of page. That is, the influence is at the same
level of THP migration.
We use the following test to measure the performance impact of the
patchset,
On a 2-socket Intel server,
- Run pmbench memory accessing benchmark
- Run `migratepages` to migrate pages of pmbench between node 0 and
node 1 back and forth.
With the patch, the TLB flushing IPI reduces 99.1% during the test and
the number of pages migrated successfully per second increases 291.7%.
Xin Hao helped to test the patchset on an ARM64 server with 128 cores,
2 NUMA nodes. Test results show that the page migration performance
increases up to 78%.
This patch (of 9):
Define struct migrate_pages_stats to organize the various statistics in
migrate_pages(). This makes it easier to collect and consume the
statistics in multiple functions. This will be needed in the following
patches in the series.
Link: https://lkml.kernel.org/r/20230213123444.155149-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20230213123444.155149-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Bharata B Rao <bharata@amd.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In hugetlb_fault(), there used to have a special path to handle swap entry
at the entrance using huge_pte_offset(). That's unsafe because
huge_pte_offset() for a pmd sharable range can access freed pgtables if
without any lock to protect the pgtable from being freed after pmd
unshare.
Here the simplest solution to make it safe is to move the swap handling to
be after the vma lock being held. We may need to take the fault mutex on
either migration or hwpoison entries now (also the vma lock, but that's
really needed), however neither of them is hot path.
Note that the vma lock cannot be released in hugetlb_fault() when the
migration entry is detected, because in migration_entry_wait_huge() the
pgtable page will be used again (by taking the pgtable lock), so that also
need to be protected by the vma lock. Modify migration_entry_wait_huge()
so that it must be called with vma read lock held, and properly release
the lock in __migration_entry_wait_huge().
Link: https://lkml.kernel.org/r/20221216155100.2043537-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull MM updates from Andrew Morton:
- More userfaultfs work from Peter Xu
- Several convert-to-folios series from Sidhartha Kumar and Huang Ying
- Some filemap cleanups from Vishal Moola
- David Hildenbrand added the ability to selftest anon memory COW
handling
- Some cpuset simplifications from Liu Shixin
- Addition of vmalloc tracing support by Uladzislau Rezki
- Some pagecache folioifications and simplifications from Matthew
Wilcox
- A pagemap cleanup from Kefeng Wang: we have VM_ACCESS_FLAGS, so use
it
- Miguel Ojeda contributed some cleanups for our use of the
__no_sanitize_thread__ gcc keyword.
This series should have been in the non-MM tree, my bad
- Naoya Horiguchi improved the interaction between memory poisoning and
memory section removal for huge pages
- DAMON cleanups and tuneups from SeongJae Park
- Tony Luck fixed the handling of COW faults against poisoned pages
- Peter Xu utilized the PTE marker code for handling swapin errors
- Hugh Dickins reworked compound page mapcount handling, simplifying it
and making it more efficient
- Removal of the autonuma savedwrite infrastructure from Nadav Amit and
David Hildenbrand
- zram support for multiple compression streams from Sergey Senozhatsky
- David Hildenbrand reworked the GUP code's R/O long-term pinning so
that drivers no longer need to use the FOLL_FORCE workaround which
didn't work very well anyway
- Mel Gorman altered the page allocator so that local IRQs can remnain
enabled during per-cpu page allocations
- Vishal Moola removed the try_to_release_page() wrapper
- Stefan Roesch added some per-BDI sysfs tunables which are used to
prevent network block devices from dirtying excessive amounts of
pagecache
- David Hildenbrand did some cleanup and repair work on KSM COW
breaking
- Nhat Pham and Johannes Weiner have implemented writeback in zswap's
zsmalloc backend
- Brian Foster has fixed a longstanding corner-case oddity in
file[map]_write_and_wait_range()
- sparse-vmemmap changes for MIPS, LoongArch and NIOS2 from Feiyang
Chen
- Shiyang Ruan has done some work on fsdax, to make its reflink mode
work better under xfstests. Better, but still not perfect
- Christoph Hellwig has removed the .writepage() method from several
filesystems. They only need .writepages()
- Yosry Ahmed wrote a series which fixes the memcg reclaim target
beancounting
- David Hildenbrand has fixed some of our MM selftests for 32-bit
machines
- Many singleton patches, as usual
* tag 'mm-stable-2022-12-13' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (313 commits)
mm/hugetlb: set head flag before setting compound_order in __prep_compound_gigantic_folio
mm: mmu_gather: allow more than one batch of delayed rmaps
mm: fix typo in struct pglist_data code comment
kmsan: fix memcpy tests
mm: add cond_resched() in swapin_walk_pmd_entry()
mm: do not show fs mm pc for VM_LOCKONFAULT pages
selftests/vm: ksm_functional_tests: fixes for 32bit
selftests/vm: cow: fix compile warning on 32bit
selftests/vm: madv_populate: fix missing MADV_POPULATE_(READ|WRITE) definitions
mm/gup_test: fix PIN_LONGTERM_TEST_READ with highmem
mm,thp,rmap: fix races between updates of subpages_mapcount
mm: memcg: fix swapcached stat accounting
mm: add nodes= arg to memory.reclaim
mm: disable top-tier fallback to reclaim on proactive reclaim
selftests: cgroup: make sure reclaim target memcg is unprotected
selftests: cgroup: refactor proactive reclaim code to reclaim_until()
mm: memcg: fix stale protection of reclaim target memcg
mm/mmap: properly unaccount memory on mas_preallocate() failure
omfs: remove ->writepage
jfs: remove ->writepage
...
Pull ext4 updates from Ted Ts'o:
"A large number of cleanups and bug fixes, with many of the bug fixes
found by Syzbot and fuzzing. (Many of the bug fixes involve less-used
ext4 features such as fast_commit, inline_data and bigalloc)
In addition, remove the writepage function for ext4, since the
medium-term plan is to remove ->writepage() entirely. (The VM doesn't
need or want writepage() for writeback, since it is fine with
->writepages() so long as ->migrate_folio() is implemented)"
* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (58 commits)
ext4: fix reserved cluster accounting in __es_remove_extent()
ext4: fix inode leak in ext4_xattr_inode_create() on an error path
ext4: allocate extended attribute value in vmalloc area
ext4: avoid unaccounted block allocation when expanding inode
ext4: initialize quota before expanding inode in setproject ioctl
ext4: stop providing .writepage hook
mm: export buffer_migrate_folio_norefs()
ext4: switch to using write_cache_pages() for data=journal writeout
jbd2: switch jbd2_submit_inode_data() to use fs-provided hook for data writeout
ext4: switch to using ext4_do_writepages() for ordered data writeout
ext4: move percpu_rwsem protection into ext4_writepages()
ext4: provide ext4_do_writepages()
ext4: add support for writepages calls that cannot map blocks
ext4: drop pointless IO submission from ext4_bio_write_page()
ext4: remove nr_submitted from ext4_bio_write_page()
ext4: move keep_towrite handling to ext4_bio_write_page()
ext4: handle redirtying in ext4_bio_write_page()
ext4: fix kernel BUG in 'ext4_write_inline_data_end()'
ext4: make ext4_mb_initialize_context return void
ext4: fix deadlock due to mbcache entry corruption
...
Pull slab updates from Vlastimil Babka:
- SLOB deprecation and SLUB_TINY
The SLOB allocator adds maintenance burden and stands in the way of
API improvements [1]. Deprecate it by renaming the config option (to
make users notice) to CONFIG_SLOB_DEPRECATED with updated help text.
SLUB should be used instead as SLAB will be the next on the removal
list.
Based on reports from a riscv k210 board with 8MB RAM, add a
CONFIG_SLUB_TINY option to minimize SLUB's memory usage at the
expense of scalability. This has resolved the k210 regression [2] so
in case there are no others (that wouldn't be resolvable by further
tweaks to SLUB_TINY) plan is to remove SLOB in a few cycles.
Existing defconfigs with CONFIG_SLOB are converted to
CONFIG_SLUB_TINY.
- kmalloc() slub_debug redzone improvements
A series from Feng Tang that builds on the tracking or requested size
for kmalloc() allocations (for caches with debugging enabled) added
in 6.1, to make redzone checks consider the requested size and not
the rounded up one, in order to catch more subtle buffer overruns.
Includes new slub_kunit test.
- struct slab fields reordering to accomodate larger rcu_head
RCU folks would like to grow rcu_head with debugging options, which
breaks current struct slab layout's assumptions, so reorganize it to
make this possible.
- Miscellaneous improvements/fixes:
- __alloc_size checking compiler workaround (Kees Cook)
- Optimize and cleanup SLUB's sysfs init (Rasmus Villemoes)
- Make SLAB compatible with PROVE_RAW_LOCK_NESTING (Jiri Kosina)
- Correct SLUB's percpu allocation estimates (Baoquan He)
- Re-enableS LUB's run-time failslab sysfs control (Alexander Atanasov)
- Make tools/vm/slabinfo more user friendly when not run as root (Rong Tao)
- Dead code removal in SLUB (Hyeonggon Yoo)
* tag 'slab-for-6.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: (31 commits)
mm, slob: rename CONFIG_SLOB to CONFIG_SLOB_DEPRECATED
mm, slub: don't aggressively inline with CONFIG_SLUB_TINY
mm, slub: remove percpu slabs with CONFIG_SLUB_TINY
mm, slub: split out allocations from pre/post hooks
mm/slub, kunit: Add a test case for kmalloc redzone check
mm/slub, kunit: add SLAB_SKIP_KFENCE flag for cache creation
mm, slub: refactor free debug processing
mm, slab: ignore SLAB_RECLAIM_ACCOUNT with CONFIG_SLUB_TINY
mm, slub: don't create kmalloc-rcl caches with CONFIG_SLUB_TINY
mm, slub: lower the default slub_max_order with CONFIG_SLUB_TINY
mm, slub: retain no free slabs on partial list with CONFIG_SLUB_TINY
mm, slub: disable SYSFS support with CONFIG_SLUB_TINY
mm, slub: add CONFIG_SLUB_TINY
mm, slab: ignore hardened usercopy parameters when disabled
slab: Remove special-casing of const 0 size allocations
slab: Clean up SLOB vs kmalloc() definition
mm/sl[au]b: rearrange struct slab fields to allow larger rcu_head
mm/migrate: make isolate_movable_page() skip slab pages
mm/slab: move and adjust kernel-doc for kmem_cache_alloc
mm/slub, percpu: correct the calculation of early percpu allocation size
...
In the next commit we want to rearrange struct slab fields to allow a larger
rcu_head. Afterwards, the page->mapping field will overlap with SLUB's "struct
list_head slab_list", where the value of prev pointer can become LIST_POISON2,
which is 0x122 + POISON_POINTER_DELTA. Unfortunately the bit 1 being set can
confuse PageMovable() to be a false positive and cause a GPF as reported by lkp
[1].
To fix this, make isolate_movable_page() skip pages with the PageSlab flag set.
This is a bit tricky as we need to add memory barriers to SLAB and SLUB's page
allocation and freeing, and their counterparts to isolate_movable_page().
Based on my RFC from [2]. Added a comment update from Matthew's variant in [3]
and, as done there, moved the PageSlab checks to happen before trying to take
the page lock.
[1] https://lore.kernel.org/all/208c1757-5edd-fd42-67d4-1940cc43b50f@intel.com/
[2] https://lore.kernel.org/all/aec59f53-0e53-1736-5932-25407125d4d4@suse.cz/
[3] https://lore.kernel.org/all/YzsVM8eToHUeTP75@casper.infradead.org/
Reported-by: kernel test robot <yujie.liu@intel.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
When creating a virtual machine, we will use memfd_create() to get a file
descriptor which can be used to create share memory mappings using the
mmap function, meanwhile the mmap() will set the MAP_POPULATE flag to
allocate physical pages for the virtual machine.
When allocating physical pages for the guest, the host can fallback to
allocate some CMA pages for the guest when over half of the zone's free
memory is in the CMA area.
In guest os, when the application wants to do some data transaction with
DMA, our QEMU will call VFIO_IOMMU_MAP_DMA ioctl to do longterm-pin and
create IOMMU mappings for the DMA pages. However, when calling
VFIO_IOMMU_MAP_DMA ioctl to pin the physical pages, we found it will be
failed to longterm-pin sometimes.
After some invetigation, we found the pages used to do DMA mapping can
contain some CMA pages, and these CMA pages will cause a possible failure
of the longterm-pin, due to failed to migrate the CMA pages. The reason
of migration failure may be temporary reference count or memory allocation
failure. So that will cause the VFIO_IOMMU_MAP_DMA ioctl returns error,
which makes the application failed to start.
I observed one migration failure case (which is not easy to reproduce) is
that, the 'thp_migration_fail' count is 1 and the 'thp_split_page_failed'
count is also 1.
That means when migrating a THP which is in CMA area, but can not allocate
a new THP due to memory fragmentation, so it will split the THP. However
THP split is also failed, probably the reason is temporary reference count
of this THP. And the temporary reference count can be caused by dropping
page caches (I observed the drop caches operation in the system), but we
can not drop the shmem page caches due to they are already dirty at that
time.
Especially for THP split failure, which is caused by temporary reference
count, we can try again to mitigate the failure of migration in this case
according to previous discussion [1].
[1] https://lore.kernel.org/all/470dc638-a300-f261-94b4-e27250e42f96@redhat.com/
Link: https://lkml.kernel.org/r/6784730480a1df82e8f4cba1ed088e4ac767994b.1666599848.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Fix several device private page reference counting issues",
v2
This series aims to fix a number of page reference counting issues in
drivers dealing with device private ZONE_DEVICE pages. These result in
use-after-free type bugs, either from accessing a struct page which no
longer exists because it has been removed or accessing fields within the
struct page which are no longer valid because the page has been freed.
During normal usage it is unlikely these will cause any problems. However
without these fixes it is possible to crash the kernel from userspace.
These crashes can be triggered either by unloading the kernel module or
unbinding the device from the driver prior to a userspace task exiting.
In modules such as Nouveau it is also possible to trigger some of these
issues by explicitly closing the device file-descriptor prior to the task
exiting and then accessing device private memory.
This involves some minor changes to both PowerPC and AMD GPU code.
Unfortunately I lack hardware to test either of those so any help there
would be appreciated. The changes mimic what is done in for both Nouveau
and hmm-tests though so I doubt they will cause problems.
This patch (of 8):
When the CPU tries to access a device private page the migrate_to_ram()
callback associated with the pgmap for the page is called. However no
reference is taken on the faulting page. Therefore a concurrent migration
of the device private page can free the page and possibly the underlying
pgmap. This results in a race which can crash the kernel due to the
migrate_to_ram() function pointer becoming invalid. It also means drivers
can't reliably read the zone_device_data field because the page may have
been freed with memunmap_pages().
Close the race by getting a reference on the page while holding the ptl to
ensure it has not been freed. Unfortunately the elevated reference count
will cause the migration required to handle the fault to fail. To avoid
this failure pass the faulting page into the migrate_vma functions so that
if an elevated reference count is found it can be checked to see if it's
expected or not.
[mpe@ellerman.id.au: fix build]
Link: https://lkml.kernel.org/r/87fsgbf3gh.fsf@mpe.ellerman.id.au
Link: https://lkml.kernel.org/r/cover.60659b549d8509ddecafad4f498ee7f03bb23c69.1664366292.git-series.apopple@nvidia.com
Link: https://lkml.kernel.org/r/d3e813178a59e565e8d78d9b9a4e2562f6494f90.1664366292.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
