When MADV_PAGEOUT is called on a private file mapping VMA region, we bail
out early if the process is neither owner nor write capable of the file. 
However, this VMA may have both private/shared clean pages and private
dirty pages.  The opportunity of paging out the private dirty pages (Anon
pages) is missed.  Fix this behavior by allowing private file mappings
pageout further and perform the file access check along with PageAnon()
during page walk.

We observe ~10% improvement in zram usage, thus leaving more available
memory on a 4GB RAM system running Android.

[quic_pkondeti@quicinc.com: v2]
  Link: https://lkml.kernel.org/r/1669962597-27724-1-git-send-email-quic_pkondeti@quicinc.com
Link: https://lkml.kernel.org/r/1667971116-12900-1-git-send-email-quic_pkondeti@quicinc.comSigned-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com>
Cc: Charan Teja Kalla <quic_charante@quicinc.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

"mm_khugepaged_collapse_file" for capturing is_shmem.
Currently, is_shmem is not being captured. Capturing is_shmem is useful
as it can indicate if tmpfs is being used as a backing store instead of
persistent storage. Add the tracepoint in collapse_file() named
"mm_khugepaged_collapse_file" for capturing is_shmem.

[gautammenghani201@gmail.com: swap is_shmem and addr to save space, per Steven Rostedt]
  Link: https://lkml.kernel.org/r/20221202201807.182829-1-gautammenghani201@gmail.com
Link: https://lkml.kernel.org/r/20221026052218.148234-1-gautammenghani201@gmail.comSigned-off-by: Gautam Menghani <gautammenghani201@gmail.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>	[tracing]
Cc: David Hildenbrand <david@redhat.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Fortunately, the last user (KSM) is gone, so let's just remove this rather
special code from generic GUP handling -- especially because KSM never
required the PMD handling as KSM only deals with individual base pages.

[akpm@linux-foundation.org: fix merge snafu]Link: https://lkml.kernel.org/r/20221021101141.84170-10-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

FOLL_MIGRATION exists only for the purpose of break_ksm(), and actually,
there is not even the need to wait for the migration to finish, we only
want to know if we're dealing with a KSM page.

Using follow_page() just to identify a KSM page overcomplicates GUP code. 
Let's use walk_page_range_vma() instead, because we don't actually care
about the page itself, we only need to know a single property -- no need
to even grab a reference.

So, get rid of follow_page() usage such that we can get rid of
FOLL_MIGRATION now and eventually be able to get rid of follow_page() in
the future.

In my setup (AMD Ryzen 9 3900X), running the KSM selftest to test unmerge
performance on 2 GiB (taskset 0x8 ./ksm_tests -D -s 2048), this results in
a performance degradation of ~2% (old: ~5010 MiB/s, new: ~4900 MiB/s).  I
don't think we particularly care for now.

Interestingly, the benchmark reduction is due to the single callback. 
Adding a second callback (e.g., pud_entry()) reduces the benchmark by
another 100-200 MiB/s.

Link: https://lkml.kernel.org/r/20221021101141.84170-9-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Let's add walk_page_range_vma(), which is similar to walk_page_vma(),
however, is only interested in a subset of the VMA range.

To be used in KSM code to stop using follow_page() next.

Link: https://lkml.kernel.org/r/20221021101141.84170-8-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Let's stop breaking COW via a fake write fault and let's use
FAULT_FLAG_UNSHARE instead.  This avoids any wrong side effects of the
fake write fault, such as mapping the PTE writable and marking the pte
dirty/softdirty.

Consequently, we will no longer trigger a fake write fault and break COW
without any such side-effects.

Also, this fixes KSM interaction with userfaultfd-wp: when we have a KSM
page that's write-protected by userfaultfd, break_ksm()->handle_mm_fault()
will fail with VM_FAULT_SIGBUS and will simply return in break_ksm() with
0 instead of actually breaking COW.

For now, the KSM unmerge tests can trigger that:
    $ sudo ./ksm_functional_tests
    TAP version 13
    1..3
    # [RUN] test_unmerge
    ok 1 Pages were unmerged
    # [RUN] test_unmerge_discarded
    ok 2 Pages were unmerged
    # [RUN] test_unmerge_uffd_wp
    not ok 3 Pages were unmerged
    Bail out! 1 out of 3 tests failed
    # Planned tests != run tests (2 != 3)
    # Totals: pass:2 fail:1 xfail:0 xpass:0 skip:0 error:0

The warning in dmesg also indicates this wrong handling:
    [  230.096368] FAULT_FLAG_ALLOW_RETRY missing 881
    [  230.100822] CPU: 1 PID: 1643 Comm: ksm-uffd-wp [...]
    [  230.110124] Hardware name: [...]
    [  230.117775] Call Trace:
    [  230.120227]  <TASK>
    [  230.122334]  dump_stack_lvl+0x44/0x5c
    [  230.126010]  handle_userfault.cold+0x14/0x19
    [  230.130281]  ? tlb_finish_mmu+0x65/0x170
    [  230.134207]  ? uffd_wp_range+0x65/0xa0
    [  230.137959]  ? _raw_spin_unlock+0x15/0x30
    [  230.141972]  ? do_wp_page+0x50/0x590
    [  230.145551]  __handle_mm_fault+0x9f5/0xf50
    [  230.149652]  ? mmput+0x1f/0x40
    [  230.152712]  handle_mm_fault+0xb9/0x2a0
    [  230.156550]  break_ksm+0x141/0x180
    [  230.159964]  unmerge_ksm_pages+0x60/0x90
    [  230.163890]  ksm_madvise+0x3c/0xb0
    [  230.167295]  do_madvise.part.0+0x10c/0xeb0
    [  230.171396]  ? do_syscall_64+0x67/0x80
    [  230.175157]  __x64_sys_madvise+0x5a/0x70
    [  230.179082]  do_syscall_64+0x58/0x80
    [  230.182661]  ? do_syscall_64+0x67/0x80
    [  230.186413]  entry_SYSCALL_64_after_hwframe+0x63/0xcd

This is primarily a fix for KSM+userfaultfd-wp, however, the fake write
fault was always questionable.  As this fix is not easy to backport and
it's not very critical, let's not cc stable.

Link: https://lkml.kernel.org/r/20221021101141.84170-6-david@redhat.com
Fixes: 529b930b ("userfaultfd: wp: hook userfault handler to write protection fault")
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

All users -- GUP and KSM -- are gone, let's just remove it.

Link: https://lkml.kernel.org/r/20221021101141.84170-4-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Now that GUP no longer requires VM_FAULT_WRITE, break_ksm() is the sole
remaining user of VM_FAULT_WRITE.  As we also want to stop triggering a
fake write fault and instead use FAULT_FLAG_UNSHARE -- similar to
GUP-triggered unsharing when taking a R/O pin on a shared anonymous page
(including KSM pages), let's stop relying on VM_FAULT_WRITE.

Let's rework break_ksm() to not rely on the return value of
handle_mm_fault() anymore to figure out whether COW-breaking was
successful.  Simply perform another follow_page() lookup to verify the
result.

While this makes break_ksm() slightly less efficient, we can simplify
handle_mm_fault() a little and easily switch to FAULT_FLAG_UNSHARE without
introducing similar KSM-specific behavior for FAULT_FLAG_UNSHARE.

In my setup (AMD Ryzen 9 3900X), running the KSM selftest to test unmerge
performance on 2 GiB (taskset 0x8 ./ksm_tests -D -s 2048), this results in
a performance degradation of ~4% -- 5% (old: ~5250 MiB/s, new: ~5010
MiB/s).

I don't think that we particularly care about that performance drop when
unmerging.  If it ever turns out to be an actual performance issue, we can
think about a better alternative for FAULT_FLAG_UNSHARE -- let's just keep
it simple for now.

Link: https://lkml.kernel.org/r/20221021101141.84170-3-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Let's add a test to measure performance of KSM breaking not triggered via
COW, but triggered by disabling KSM on an area filled with KSM pages via
MADV_UNMERGEABLE.

Link: https://lkml.kernel.org/r/20221021101141.84170-2-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

As Peter points out, the caller passes a single VMA and can just do that
check itself.

And in fact, no existing users rely on test_walk() getting called.  So
let's just remove it and make the implementation slightly more efficient.

Link: https://lkml.kernel.org/r/20221021101141.84170-7-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "mm/ksm: break_ksm() cleanups and fixes", v2.

This series cleans up and fixes break_ksm().  In summary, we no longer use
fake write faults to break COW but instead FAULT_FLAG_UNSHARE.  Further,
we move away from using follow_page() --- that we can hopefully remove
completely at one point --- and use new walk_page_range_vma() instead.

Fortunately, we can get rid of VM_FAULT_WRITE and FOLL_MIGRATION in common
code now.

Extend the existing ksm tests by an unmerge benchmark, and a some new
unmerge tests.

Also, add a selftest to measure MADV_UNMERGEABLE performance.  In my setup
(AMD Ryzen 9 3900X), running the KSM selftest to test unmerge performance
on 2 GiB (taskset 0x8 ./ksm_tests -D -s 2048), this results in a
performance degradation of ~6% -- 7% (old: ~5250 MiB/s, new: ~4900 MiB/s).
I don't think we particularly care for now, but it's good to be aware of
the implication.


This patch (of 9):

Let's add three unmerge tests (MADV_UNMERGEABLE unmerging all pages in the
range).

test_unmerge(): basic unmerge tests
test_unmerge_discarded(): have some pte_none() entries in the range
test_unmerge_uffd_wp(): protect the merged pages using uffd-wp

ksm_tests.c currently contains a mixture of benchmarks and tests, whereby
each test is carried out by executing the ksm_tests binary with specific
parameters.  Let's add new ksm_functional_tests.c that performs multiple,
smaller functional tests all at once.

Link: https://lkml.kernel.org/r/20221021101141.84170-1-david@redhat.com
Link: https://lkml.kernel.org/r/20221021101141.84170-5-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Our memory management kernel CI testing at Red Hat uses the VM
selftests and we have run into two problems:

First, our LTP tests overlap with the VM selftests.

We want to avoid unhelpful redundancy in our testing practices.

Second, we have observed the current run_vmtests.sh to report overall
failure/ambiguous results in the case that a machine lacks the necessary
hardware to perform one or more of the tests. E.g. ksm tests that
require more than one numa node.

We want to be able to run the vm selftests suitable to particular hardware.

Add the ability to run one or more groups of vm tests via run_vmtests.sh
instead of simply all-or-none in order to solve these problems.

Preserve existing default behavior of running all tests when the script
is invoked with no arguments.

Documentation of test groups is included in the patch as follows:

    # ./run_vmtests.sh [ -h || --help ]

    usage: ./tools/testing/selftests/vm/run_vmtests.sh [ -h | -t "<categories>"]
      -t: specify specific categories to tests to run
      -h: display this message

    The default behavior is to run all tests.

    Alternatively, specific groups tests can be run by passing a string
    to the -t argument containing one or more of the following categories
    separated by spaces:
    - mmap
	    tests for mmap(2)
    - gup_test
	    tests for gup using gup_test interface
    - userfaultfd
	    tests for  userfaultfd(2)
    - compaction
	    a test for the patch "Allow compaction of unevictable pages"
    - mlock
	    tests for mlock(2)
    - mremap
	    tests for mremap(2)
    - hugevm
	    tests for very large virtual address space
    - vmalloc
	    vmalloc smoke tests
    - hmm
	    hmm smoke tests
    - madv_populate
	    test memadvise(2) MADV_POPULATE_{READ,WRITE} options
    - memfd_secret
	    test memfd_secret(2)
    - process_mrelease
	    test process_mrelease(2)
    - ksm
	    ksm tests that do not require >=2 NUMA nodes
    - ksm_numa
	    ksm tests that require >=2 NUMA nodes
    - pkey
	    memory protection key tests
    - soft_dirty
    	    test soft dirty page bit semantics
    - anon_cow
            test anonymous copy-on-write semantics
    example: ./run_vmtests.sh -t "hmm mmap ksm"

Link: https://lkml.kernel.org/r/20221018231222.1884715-1-jsavitz@redhat.comSigned-off-by: Joel Savitz <jsavitz@redhat.com>
Cc: Joel Savitz <jsavitz@redhat.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

memcg_write_event_control() accesses the dentry->d_name of the specified
control fd to route the write call.  As a cgroup interface file can't be
renamed, it's safe to access d_name as long as the specified file is a
regular cgroup file.  Also, as these cgroup interface files can't be
removed before the directory, it's safe to access the parent too.

Prior to 347c4a87 ("memcg: remove cgroup_event->cft"), there was a
call to __file_cft() which verified that the specified file is a regular
cgroupfs file before further accesses.  The cftype pointer returned from
__file_cft() was no longer necessary and the commit inadvertently dropped
the file type check with it allowing any file to slip through.  With the
invarients broken, the d_name and parent accesses can now race against
renames and removals of arbitrary files and cause use-after-free's.

Fix the bug by resurrecting the file type check in __file_cft().  Now that
cgroupfs is implemented through kernfs, checking the file operations needs
to go through a layer of indirection.  Instead, let's check the superblock
and dentry type.

Link: https://lkml.kernel.org/r/Y5FRm/cfcKPGzWwl@slm.duckdns.org
Fixes: 347c4a87 ("memcg: remove cgroup_event->cft")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jann Horn <jannh@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: <stable@vger.kernel.org>	[3.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

I'm moving to the @linux.dev account.  Map my old addresses and update it
to my new address.

Link: https://lkml.kernel.org/r/20221208115548.85244-1-songmuchun@bytedance.comSigned-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

For dax pud, pud_huge() returns true on x86. So the function works as long
as hugetlb is configured. However, dax doesn't depend on hugetlb.
Commit 414fd080 ("mm/gup: fix gup_pmd_range() for dax") fixed
devmap-backed huge PMDs, but missed devmap-backed huge PUDs. Fix this as
well.

This fixes the below kernel panic:

general protection fault, probably for non-canonical address 0x69e7c000cc478: 0000 [#1] SMP
	< snip >
Call Trace:
<TASK>
get_user_pages_fast+0x1f/0x40
iov_iter_get_pages+0xc6/0x3b0
? mempool_alloc+0x5d/0x170
bio_iov_iter_get_pages+0x82/0x4e0
? bvec_alloc+0x91/0xc0
? bio_alloc_bioset+0x19a/0x2a0
blkdev_direct_IO+0x282/0x480
? __io_complete_rw_common+0xc0/0xc0
? filemap_range_has_page+0x82/0xc0
generic_file_direct_write+0x9d/0x1a0
? inode_update_time+0x24/0x30
__generic_file_write_iter+0xbd/0x1e0
blkdev_write_iter+0xb4/0x150
? io_import_iovec+0x8d/0x340
io_write+0xf9/0x300
io_issue_sqe+0x3c3/0x1d30
? sysvec_reschedule_ipi+0x6c/0x80
__io_queue_sqe+0x33/0x240
? fget+0x76/0xa0
io_submit_sqes+0xe6a/0x18d0
? __fget_light+0xd1/0x100
__x64_sys_io_uring_enter+0x199/0x880
? __context_tracking_enter+0x1f/0x70
? irqentry_exit_to_user_mode+0x24/0x30
? irqentry_exit+0x1d/0x30
? __context_tracking_exit+0xe/0x70
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fc97c11a7be
	< snip >
</TASK>
---[ end trace 48b2e0e67debcaeb ]---
RIP: 0010:internal_get_user_pages_fast+0x340/0x990
	< snip >
Kernel panic - not syncing: Fatal exception
Kernel Offset: disabled

Link: https://lkml.kernel.org/r/1670392853-28252-1-git-send-email-ssengar@linux.microsoft.com
Fixes: 414fd080 ("mm/gup: fix gup_pmd_range() for dax")
Signed-off-by: John Starks <jostarks@microsoft.com>
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Add more sanity checks to the VMA that do_brk_flags() will expand.  Ensure
the VMA matches basic merge requirements within the function before
calling can_vma_merge_after().

Drop the duplicate checks from vm_brk_flags() since they will be enforced
later.

The old code would expand file VMAs on brk(), which is functionally
wrong and also dangerous in terms of locking because the brk() path
isn't designed for file VMAs and therefore doesn't lock the file
mapping.  Checking can_vma_merge_after() ensures that new anonymous
VMAs can't be merged into file VMAs.

See https://lore.kernel.org/linux-mm/CAG48ez1tJZTOjS_FjRZhvtDA-STFmdw8PEizPDwMGFd_ui0Nrw@mail.gmail.com/

Link: https://lkml.kernel.org/r/20221205192304.1957418-1-Liam.Howlett@oracle.com
Fixes: 2e7ce7d3 ("mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()")
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: Jann Horn <jannh@google.com>
Cc: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

We use "unsigned long" to store a PFN in the kernel and phys_addr_t to
store a physical address.

On a 64bit system, both are 64bit wide.  However, on a 32bit system, the
latter might be 64bit wide.  This is, for example, the case on x86 with
PAE: phys_addr_t and PTEs are 64bit wide, while "unsigned long" only spans
32bit.

The current definition of SWP_PFN_BITS without MAX_PHYSMEM_BITS misses
that case, and assumes that the maximum PFN is limited by an 32bit
phys_addr_t.  This implies, that SWP_PFN_BITS will currently only be able
to cover 4 GiB - 1 on any 32bit system with 4k page size, which is wrong.

Let's rely on the number of bits in phys_addr_t instead, but make sure to
not exceed the maximum swap offset, to not make the BUILD_BUG_ON() in
is_pfn_swap_entry() unhappy.  Note that swp_entry_t is effectively an
unsigned long and the maximum swap offset shares that value with the swap
type.

For example, on an 8 GiB x86 PAE system with a kernel config based on
Debian 11.5 (-> CONFIG_FLATMEM=y, CONFIG_X86_PAE=y), we will currently
fail removing migration entries (remove_migration_ptes()), because
mm/page_vma_mapped.c:check_pte() will fail to identify a PFN match as
swp_offset_pfn() wrongly masks off PFN bits.  For example,
split_huge_page_to_list()->...->remap_page() will leave migration entries
in place and continue to unlock the page.

Later, when we stumble over these migration entries (e.g., via
/proc/self/pagemap), pfn_swap_entry_to_page() will BUG_ON() because these
migration entries shouldn't exist anymore and the page was unlocked.

[   33.067591] kernel BUG at include/linux/swapops.h:497!
[   33.067597] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
[   33.067602] CPU: 3 PID: 742 Comm: cow Tainted: G            E      6.1.0-rc8+ #16
[   33.067605] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.fc36 04/01/2014
[   33.067606] EIP: pagemap_pmd_range+0x644/0x650
[   33.067612] Code: 00 00 00 00 66 90 89 ce b9 00 f0 ff ff e9 ff fb ff ff 89 d8 31 db e8 48 c6 52 00 e9 23 fb ff ff e8 61 83 56 00 e9 b6 fe ff ff <0f> 0b bf 00 f0 ff ff e9 38 fa ff ff 3e 8d 74 26 00 55 89 e5 57 31
[   33.067615] EAX: ee394000 EBX: 00000002 ECX: ee394000 EDX: 00000000
[   33.067617] ESI: c1b0ded4 EDI: 00024a00 EBP: c1b0ddb4 ESP: c1b0dd68
[   33.067619] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 EFLAGS: 00010246
[   33.067624] CR0: 80050033 CR2: b7a00000 CR3: 01bbbd20 CR4: 00350ef0
[   33.067625] Call Trace:
[   33.067628]  ? madvise_free_pte_range+0x720/0x720
[   33.067632]  ? smaps_pte_range+0x4b0/0x4b0
[   33.067634]  walk_pgd_range+0x325/0x720
[   33.067637]  ? mt_find+0x1d6/0x3a0
[   33.067641]  ? mt_find+0x1d6/0x3a0
[   33.067643]  __walk_page_range+0x164/0x170
[   33.067646]  walk_page_range+0xf9/0x170
[   33.067648]  ? __kmem_cache_alloc_node+0x2a8/0x340
[   33.067653]  pagemap_read+0x124/0x280
[   33.067658]  ? default_llseek+0x101/0x160
[   33.067662]  ? smaps_account+0x1d0/0x1d0
[   33.067664]  vfs_read+0x90/0x290
[   33.067667]  ? do_madvise.part.0+0x24b/0x390
[   33.067669]  ? debug_smp_processor_id+0x12/0x20
[   33.067673]  ksys_pread64+0x58/0x90
[   33.067675]  __ia32_sys_ia32_pread64+0x1b/0x20
[   33.067680]  __do_fast_syscall_32+0x4c/0xc0
[   33.067683]  do_fast_syscall_32+0x29/0x60
[   33.067686]  do_SYSENTER_32+0x15/0x20
[   33.067689]  entry_SYSENTER_32+0x98/0xf1

Decrease the indentation level of SWP_PFN_BITS and SWP_PFN_MASK to keep it
readable and consistent.

[david@redhat.com: rely on sizeof(phys_addr_t) and min_t() instead]
  Link: https://lkml.kernel.org/r/20221206105737.69478-1-david@redhat.com
[david@redhat.com: use "int" for comparison, as we're only comparing numbers < 64]
  Link: https://lkml.kernel.org/r/1f157500-2676-7cef-a84e-9224ed64e540@redhat.com
Link: https://lkml.kernel.org/r/20221205150857.167583-1-david@redhat.com
Fixes: 0d206b5d ("mm/swap: add swp_offset_pfn() to fetch PFN from swap entry")
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Fix tmpfs data loss when the fallocate system call is interrupted by a
signal, or fails for some other reason.  The partial folio handling in
shmem_undo_range() forgot to consider this unfalloc case, and was liable
to erase or truncate out data which had already been committed earlier.

It turns out that none of the partial folio handling there is appropriate
for the unfalloc case, which just wants to proceed to removal of whole
folios: which find_get_entries() provides, even when partially covered.

Original patch by Rui Wang.

Link: https://lore.kernel.org/linux-mm/33b85d82.7764.1842e9ab207.Coremail.chenguoqic@163.com/
Link: https://lkml.kernel.org/r/a5dac112-cf4b-7af-a33-f386e347fd38@google.com
Fixes: b9a8a419 ("truncate,shmem: Handle truncates that split large folios")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: Guoqi Chen <chenguoqic@163.com>
  Link: https://lore.kernel.org/all/20221101032248.819360-1-kernel@hev.cc/
Cc: Rui Wang <kernel@hev.cc>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: <stable@vger.kernel.org>	[5.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1813e51e ("memcg: increase MEMCG_CHARGE_BATCH to 64") has changed
the batch size while this test case has been left behind. This has led
to a test failure reported by test bot:
not ok 2 selftests: cgroup: test_kmem # exit=1

Update the tolerance for the pcp charges to reflect the
MEMCG_CHARGE_BATCH change to fix this.

[akpm@linux-foundation.org: update comments, per Roman]
Link: https://lkml.kernel.org/r/Y4m8Unt6FhWKC6IH@dhcp22.suse.cz
Fixes: 1813e51e ("memcg: increase MEMCG_CHARGE_BATCH to 64")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: kernel test robot <yujie.liu@intel.com>
  Link: https://lore.kernel.org/oe-lkp/202212010958.c1053bd3-yujie.liu@intel.comAcked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Michal Koutný" <mkoutny@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The following program will trigger the BUG_ON that this patch removes,
because the user can munmap() mm->brk:

  #include <sys/syscall.h>
  #include <sys/mman.h>
  #include <assert.h>
  #include <unistd.h>

  static void *brk_now(void)
  {
    return (void *)syscall(SYS_brk, 0);
  }

  static void brk_set(void *b)
  {
    assert(syscall(SYS_brk, b) != -1);
  }

  int main(int argc, char *argv[])
  {
    void *b = brk_now();
    brk_set(b + 4096);
    assert(munmap(b - 4096, 4096 * 2) == 0);
    brk_set(b);
    return 0;
  }

Compile that with musl, since glibc actually uses brk(), and then
execute it, and it'll hit this splat:

  kernel BUG at mm/mmap.c:229!
  invalid opcode: 0000 [#1] PREEMPT SMP
  CPU: 12 PID: 1379 Comm: a.out Tainted: G S   U             6.1.0-rc7+ #419
  RIP: 0010:__do_sys_brk+0x2fc/0x340
  Code: 00 00 4c 89 ef e8 04 d3 fe ff eb 9a be 01 00 00 00 4c 89 ff e8 35 e0 fe ff e9 6e ff ff ff 4d 89 a7 20>
  RSP: 0018:ffff888140bc7eb0 EFLAGS: 00010246
  RAX: 0000000000000000 RBX: 00000000007e7000 RCX: ffff8881020fe000
  RDX: ffff8881020fe001 RSI: ffff8881955c9b00 RDI: ffff8881955c9b08
  RBP: 0000000000000000 R08: ffff8881955c9b00 R09: 00007ffc77844000
  R10: 0000000000000000 R11: 0000000000000001 R12: 00000000007e8000
  R13: 00000000007e8000 R14: 00000000007e7000 R15: ffff8881020fe000
  FS:  0000000000604298(0000) GS:ffff88901f700000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000603fe0 CR3: 000000015ba9a005 CR4: 0000000000770ee0
  PKRU: 55555554
  Call Trace:
   <TASK>
   do_syscall_64+0x2b/0x50
   entry_SYSCALL_64_after_hwframe+0x46/0xb0
  RIP: 0033:0x400678
  Code: 10 4c 8d 41 08 4c 89 44 24 10 4c 8b 01 8b 4c 24 08 83 f9 2f 77 0a 4c 8d 4c 24 20 4c 01 c9 eb 05 48 8b>
  RSP: 002b:00007ffc77863890 EFLAGS: 00000212 ORIG_RAX: 000000000000000c
  RAX: ffffffffffffffda RBX: 000000000040031b RCX: 0000000000400678
  RDX: 00000000004006a1 RSI: 00000000007e6000 RDI: 00000000007e7000
  RBP: 00007ffc77863900 R08: 0000000000000000 R09: 00000000007e6000
  R10: 00007ffc77863930 R11: 0000000000000212 R12: 00007ffc77863978
  R13: 00007ffc77863988 R14: 0000000000000000 R15: 0000000000000000
   </TASK>

Instead, just return the old brk value if the original mapping has been
removed.

[akpm@linux-foundation.org: fix changelog, per Liam]
Link: https://lkml.kernel.org/r/20221202162724.2009-1-Jason@zx2c4.com
Fixes: 2e7ce7d3 ("mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The email backend used by ROHM keeps labeling patches as spam.  This can
result in missing the patches.

Switch my mail address from a company mail to a personal one.

Link: https://lkml.kernel.org/r/8f4498b66fedcbded37b3b87e0c516e659f8f583.1669912977.git.mazziesaccount@gmail.comSigned-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Suggested-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Anup Patel <anup@brainfault.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Atish Patra <atishp@atishpatra.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Ben Widawsky <bwidawsk@kernel.org>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Kirill Tkhai <tkhai@ya.ru>
Cc: Qais Yousef <qyousef@layalina.io>
Cc: Vasily Averin <vasily.averin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If freeit is true, the value of ret must be zero, there is no need to
check the value of freeit after label unlock_mutex.

We can drop variable freeit to do this cleanup.

Link: https://lkml.kernel.org/r/20221125065444.3462681-1-mawupeng1@huawei.comSigned-off-by: Ma Wupeng <mawupeng1@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: zhenwei pi <pizhenwei@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

We used to have 624a2c94 (Partly revert "mm/thp: carry over dirty bit
when thp splits on pmd") fixing the regression reported here by Anatoly
Pugachev on sparc64:

https://lore.kernel.org/r/20221021160603.GA23307@u164.east.ru

Where we temporarily ignored the dirty bit for small pages.

Then, Hev also reported similar issue on loongarch:

(the original mail was private, but Anatoly copied the list here)

https://lore.kernel.org/r/CADxRZqxqb7f_WhMh=jweZP+ynf_JwGd-0VwbYgp4P+T0-AXosw@mail.gmail.com

Hev pointed out that the issue is having HW write bit set within the
pte_mkdirty() so the split pte can be written after split even if e.g. 
they were shared by more than one processes, causing data corrupt.

Hev also tried to explain why loongarch set HW write bit in mkdirty:

https://lore.kernel.org/r/CAHirt9itKO_K_HPboXh5AyJtt16Zf0cD73PtHvM=na39u_ztxA@mail.gmail.com

One way to fix it is as what Huacai proposed here for loongarch (then we
can re-apply the dirty bit in thp split):

https://lore.kernel.org/r/20221117042532.4064448-1-chenhuacai@loongson.cnn

We may need similar thing for sparc64, though.

For now since we've found the root cause of the dirty bit issue the
simpler solution (which won't lose the dirty bit for small) that will work
for both is we wr-protect after pte_mkdirty(), so the HW write bit can be
persistent after thp split.

Add a comment for wrprotect, so we will not mess up the ordering later.

With 624a2c94 (Partly revert "mm/thp: carry over dirty bit when thp
splits on pmd") this is not a fix anymore, but just brings back the dirty
bit for thp split safely, so we re-apply the optimization but in safe way.

Provide a Tested-by credit to Hev too (not the exact same patch but the
same outcome) for loongarch.

Link: https://lkml.kernel.org/r/20221125185857.3110155-1-peterx@redhat.comSigned-off-by: Peter Xu <peterx@redhat.com>
Tested-by: Hev <r@hev.cc> # loongarch
Cc: Anatoly Pugachev <matorola@gmail.com>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Replace open-coded snprintf() with sysfs_emit() to simplify the code.

Link: https://lkml.kernel.org/r/202211241929015476424@zte.com.cnSigned-off-by: Xu Panda <xu.panda@zte.com.cn>
Signed-off-by: Yang Yang <yang.yang29@zte.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

In __gmap_segment_gaddr() pmd level page table page is being extracted
from the pmd pointer, similar to pmd_pgtable_page() implementation.  This
reduces some redundancy by directly using pmd_pgtable_page() instead,
though first making it available.

Link: https://lkml.kernel.org/r/20221125034502.1559986-1-anshuman.khandual@arm.comSigned-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Current pmd_to_page(), which derives the page table page containing the
pmd address has a very misleading name.  The problem being, it sounds
similar to pmd_page() which derives page embedded in a given pmd entry
either for next level page or a mapped huge page.  Rename it as
pmd_pgtable_page() instead.

Link: https://lkml.kernel.org/r/20221124131641.1523772-1-anshuman.khandual@arm.comSigned-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

zswap_frontswap_load() should be called from preemptible context (we even
call mutex_lock() there) and it does not look like we need to do
GFP_ATOMIC allocaion for temp buffer.  The same applies to
zswap_writeback_entry().

Use GFP_KERNEL for temporary buffer allocation in both cases.

Link: https://lkml.kernel.org/r/Y3xCTr6ikbtcUr/y@google.comSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Although pmd_present() might seem to indicate a valid and mapped pmd
entry, in reality it returns true when pmd_page() points to a valid page
in memory , regardless whether the pmd entry is mapped or not.  Andrea
Arcangeli had earlier explained [1] the required semantics for
pmd_present().  This just updates the documentation for pmd_present() as
required.

[1] https://lore.kernel.org/lkml/20181017020930.GN30832@redhat.com/

Link: https://lkml.kernel.org/r/20221123051319.1312582-1-anshuman.khandual@arm.comSigned-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Depending on the memory configuration, isolate_freepages_block() may scan
pages out of the target range and causes panic.

Panic can occur on systems with multiple zones in a single pageblock.

The reason it is rare is that it only happens in special
configurations.  Depending on how many similar systems there are, it
may be a good idea to fix this problem for older kernels as well.

The problem is that pfn as argument of fast_isolate_around() could be out
of the target range.  Therefore we should consider the case where pfn <
start_pfn, and also the case where end_pfn < pfn.

This problem should have been addressd by the commit 6e2b7044 ("mm,
compaction: make fast_isolate_freepages() stay within zone") but there was
an oversight.

 Case1: pfn < start_pfn

  <at memory compaction for node Y>
  |  node X's zone  | node Y's zone
  +-----------------+------------------------------...
   pageblock    ^   ^     ^
  +-----------+-----------+-----------+-----------+...
                ^   ^     ^
                ^   ^      end_pfn
                ^    start_pfn = cc->zone->zone_start_pfn
                 pfn
                <---------> scanned range by "Scan After"

 Case2: end_pfn < pfn

  <at memory compaction for node X>
  |  node X's zone  | node Y's zone
  +-----------------+------------------------------...
   pageblock  ^     ^   ^
  +-----------+-----------+-----------+-----------+...
              ^     ^   ^
              ^     ^    pfn
              ^      end_pfn
               start_pfn
              <---------> scanned range by "Scan Before"

It seems that there is no good reason to skip nr_isolated pages just after
given pfn.  So let perform simple scan from start to end instead of
dividing the scan into "Before" and "After".

Link: https://lkml.kernel.org/r/20221026112438.236336-1-a.naribayashi@fujitsu.com
Fixes: 6e2b7044 ("mm, compaction: make fast_isolate_freepages() stay within zone").
Signed-off-by: NARIBAYASHI Akira <a.naribayashi@fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This documents the new /sys/class/bdi/<bdi>/max_ratio_fine knob.

[akpm@linux-foundation.org: fix htmldocs warnings]
Link: https://lkml.kernel.org/r/20221119005215.3052436-21-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This adds the min_ratio_fine knob. The knob specifies the values not
based on 1 of 100, but instead 1 per million.

Link: https://lkml.kernel.org/r/20221119005215.3052436-20-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This introduces bdi_set_min_ratio_no_scale(). It uses the max
granularity for the ratio. This function by the new sysfs knob
min_ratio_fine.

Link: https://lkml.kernel.org/r/20221119005215.3052436-19-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This documents the new /sys/class/bdi/<bdi>/max_ratio_fine knob.

[akpm@linux-foundation.org: fix htmldocs warnings]
Link: https://lkml.kernel.org/r/20221119005215.3052436-18-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This adds the max_ratio_fine knob. The knob specifies the values not
based on 1 of 100, but instead 1 per million.

Link: https://lkml.kernel.org/r/20221119005215.3052436-17-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This introduces bdi_set_max_ratio_no_scale(). It uses the max
granularity for the ratio. This function by the new sysfs knob
max_ratio_fine.

Link: https://lkml.kernel.org/r/20221119005215.3052436-16-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This documents the new /sys/class/bdi/<bdi>/min_bytes knob.

[akpm@linux-foundation.org: fix htmldocs warnings]
Link: https://lkml.kernel.org/r/20221119005215.3052436-15-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

bdi has two existing knobs to limit the amount of dirty memory:
min_ratio and max_ratio. However the granularity of the knobs is limited
and often it is more convenient to specify limits in terms of bytes.
This change adds the min_bytes knob.

It does not store the min_bytes value, instead it converts the max_bytes
value to a ratio. The value is therefore more an approximation than an
absolute value.

It also maintains the sum over all the bdi min_ratio values stored in
the variable bdi_min_ratio.

Link: https://lkml.kernel.org/r/20221119005215.3052436-14-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This introduces the bdi_set_min_bytes() function. The min_bytes function
does not store the min_bytes value. Instead it converts the min_bytes
value into the corresponding ratio value.

Link: https://lkml.kernel.org/r/20221119005215.3052436-13-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This splits off the __bdi_set_min_ratio() function from the
bdi_set_min_ratio() function. The __bdi_set_min_ratio() function will
also be called from the bdi_set_min_bytes() function, which will be
introduced in the next patch.

Link: https://lkml.kernel.org/r/20221119005215.3052436-12-shr@devkernel.ioSigned-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>