linux-stable.git/include/linux/shmem_fs.h, branch v6.5.2

userfaultfd: convert mfill_atomic() to use a folio

2023-04-18T23:29:55+00:00

Convert mfill_atomic_pte_copy(), shmem_mfill_atomic_pte() and
mfill_atomic_pte() to take in a folio pointer.

Convert mfill_atomic() to use a folio.  Convert page_kaddr to kaddr in
mfill_atomic().

Link: https://lkml.kernel.org/r/20230410133932.32288-7-zhangpeng362@huawei.com
Signed-off-by: ZhangPeng 
Reviewed-by: Mike Kravetz 
Cc: Kefeng Wang 
Cc: Matthew Wilcox 
Cc: Muchun Song 
Cc: Nanyong Sun 
Cc: Sidhartha Kumar 
Cc: Vishal Moola (Oracle) 
Signed-off-by: Andrew Morton

smaps: fix defined but not used smaps_shmem_walk_ops

2023-04-18T23:29:54+00:00

When !CONFIG_SHMEM smaps_shmem_walk_ops is defined but not used,
triggering a compiler warning.  To avoid the warning remove the #ifdef
around the usage.  This has no effect because shmem_mapping() is a stub
returning false when !CONFIG_SHMEM so the code will be compiled out,
however we now need to also provide a stub for shmem_swap_usage().

Link: https://lkml.kernel.org/r/20230405103819.151246-1-steven.price@arm.com
Fixes: 7b86ac3371b7 ("pagewalk: separate function pointers from iterator data")
Signed-off-by: Steven Price 
Reported-by: kernel test robot 
  Link: https://lore.kernel.org/oe-kbuild-all/202304031749.UiyJpxzF-lkp@intel.com/
Reviewed-by: Jason Gunthorpe 
Cc: Christoph Hellwig 
Cc: Alexey Dobriyan 
Cc: Thomas Hellström 
Signed-off-by: Andrew Morton

mm: userfaultfd: combine 'mode' and 'wp_copy' arguments

2023-04-06T02:42:48+00:00

Many userfaultfd ioctl functions take both a 'mode' and a 'wp_copy'
argument.  In future commits we plan to plumb the flags through to more
places, so we'd be proliferating the very long argument list even further.

Let's take the time to simplify the argument list.  Combine the two
arguments into one - and generalize, so when we add more flags in the
future, it doesn't imply more function arguments.

Since the modes (copy, zeropage, continue) are mutually exclusive, store
them as an integer value (0, 1, 2) in the low bits.  Place combine-able
flag bits in the high bits.

This is quite similar to an earlier patch proposed by Nadav Amit
("userfaultfd: introduce uffd_flags" [1]).  The main difference is that
patch only handled flags, whereas this patch *also* combines the "mode"
argument into the same type to shorten the argument list.

[1]: https://lore.kernel.org/all/20220619233449.181323-2-namit@vmware.com/

Link: https://lkml.kernel.org/r/20230314221250.682452-4-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen 
Acked-by: James Houghton 
Acked-by: Peter Xu 
Acked-by: Mike Rapoport (IBM) 
Cc: Al Viro 
Cc: Hugh Dickins 
Cc: Jan Kara 
Cc: Liam R. Howlett 
Cc: Matthew Wilcox (Oracle) 
Cc: Mike Kravetz 
Cc: Muchun Song 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton

mm: userfaultfd: don't pass around both mm and vma

2023-04-06T02:42:47+00:00

Quite a few userfaultfd functions took both mm and vma pointers as
arguments.  Since the mm is trivially accessible via vma->vm_mm, there's
no reason to pass both; it just needlessly extends the already long
argument list.

Get rid of the mm pointer, where possible, to shorten the argument list.

Link: https://lkml.kernel.org/r/20230314221250.682452-3-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen 
Acked-by: Peter Xu 
Acked-by: Mike Rapoport (IBM) 
Cc: Al Viro 
Cc: Hugh Dickins 
Cc: James Houghton 
Cc: Jan Kara 
Cc: Liam R. Howlett 
Cc: Matthew Wilcox (Oracle) 
Cc: Mike Kravetz 
Cc: Muchun Song 
Cc: Nadav Amit 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton

shmem: add support to ignore swap

2023-03-28T23:20:15+00:00

In doing experimentations with shmem having the option to avoid swap
becomes a useful mechanism.  One of the *raves* about brd over shmem is
you can avoid swap, but that's not really a good reason to use brd if we
can instead use shmem.  Using brd has its own good reasons to exist, but
just because "tmpfs" doesn't let you do that is not a great reason to
avoid it if we can easily add support for it.

I don't add support for reconfiguring incompatible options, but if we
really wanted to we can add support for that.

To avoid swap we use mapping_set_unevictable() upon inode creation, and
put a WARN_ON_ONCE() stop-gap on writepages() for reclaim.

Link: https://lkml.kernel.org/r/20230309230545.2930737-7-mcgrof@kernel.org
Signed-off-by: Luis Chamberlain 
Acked-by: Christian Brauner 
Tested-by: Xin Hao 
Reviewed-by: Davidlohr Bueso 
Cc: Adam Manzanares 
Cc: David Hildenbrand 
Cc: Davidlohr Bueso 
Cc: Hugh Dickins 
Cc: Kees Cook 
Cc: Matthew Wilcox 
Cc: Pankaj Raghav 
Cc: Yosry Ahmed 
Signed-off-by: Andrew Morton

shmem: add shmem_read_folio() and shmem_read_folio_gfp()

2023-02-10T00:51:42+00:00

These are the folio replacements for shmem_read_mapping_page() and
shmem_read_mapping_page_gfp().

[akpm@linux-foundation.org: fix shmem_read_mapping_page_gfp(), per Matthew]
  Link: https://lkml.kernel.org/r/Y+QdJTuzxeBYejw2@casper.infradead.org
Link: https://lkml.kernel.org/r/20230206162520.4029022-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Cc: Mark Hemment 
Cc: Charan Teja Kalla 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Michal Hocko 
Cc: Pavankumar Kondeti 
Cc: Shakeel Butt 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

mm: fix khugepaged with shmem_enabled=advise

2023-02-03T06:33:13+00:00

Pass vm_flags as a parameter to shmem_is_huge, rather than reading the
flags from the vm_area_struct in question.  This allows the updated flags
from hugepage_madvise to be passed to the check, which is necessary
because madvise does not update the vm_area_struct's flags until after
hugepage_madvise returns.

This fixes an issue when shmem_enabled=madvise, where MADV_HUGEPAGE on
shmem was not able to register the mm_struct with khugepaged.  Prior to
cd89fb065099, the mm_struct was registered by MADV_HUGEPAGE regardless of
the value of shmem_enabled (which was only checked when scanning vmas).

Link: https://lkml.kernel.org/r/20230113023011.1784015-1-stevensd@google.com
Fixes: cd89fb065099 ("mm,thp,shmem: make khugepaged obey tmpfs mount flags")
Signed-off-by: David Stevens 
Cc: David Stevens 
Cc: Hugh Dickins 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton

mm/shmem: add flag to enforce shmem THP in hugepage_vma_check()

2022-10-03T21:03:33+00:00

Patch series "mm: add file/shmem support to MADV_COLLAPSE", v4.

This series builds on top of the previous "mm: userspace hugepage
collapse" series which introduced the MADV_COLLAPSE madvise mode and added
support for private, anonymous mappings[2], by adding support for file and
shmem backed memory to CONFIG_READ_ONLY_THP_FOR_FS=y kernels.

File and shmem support have been added with effort to align with existing
MADV_COLLAPSE semantics and policy decisions[3].  Collapse of shmem-backed
memory ignores kernel-guiding directives and heuristics including all
sysfs settings (transparent_hugepage/shmem_enabled), and tmpfs huge= mount
options (shmem always supports large folios).  Like anonymous mappings, on
successful return of MADV_COLLAPSE on file/shmem memory, the contents of
memory mapped by the addresses provided will be synchronously pmd-mapped
THPs.

This functionality unlocks two important uses:

(1)	Immediately back executable text by THPs.  Current support provided
	by CONFIG_READ_ONLY_THP_FOR_FS may take a long time on a large
	system which might impair services from serving at their full rated
	load after (re)starting.  Tricks like mremap(2)'ing text onto
	anonymous memory to immediately realize iTLB performance prevents
	page sharing and demand paging, both of which increase steady state
	memory footprint.  Now, we can have the best of both worlds: Peak
	upfront performance and lower RAM footprints.

(2)	userfaultfd-based live migration of virtual machines satisfy UFFD
	faults by fetching native-sized pages over the network (to avoid
	latency of transferring an entire hugepage).  However, after guest
	memory has been fully copied to the new host, MADV_COLLAPSE can
	be used to immediately increase guest performance.

khugepaged has received a small improvement by association and can now
detect and collapse pte-mapped THPs.  However, there is still work to be
done along the file collapse path.  Compound pages of arbitrary order
still needs to be supported and THP collapse needs to be converted to
using folios in general.  Eventually, we'd like to move away from the
read-only and executable-mapped constraints currently imposed on eligible
files and support any inode claiming huge folio support.  That said, I
think the series as-is covers enough to claim that MADV_COLLAPSE supports
file/shmem memory.

Patches 1-3	Implement the guts of the series.
Patch 4 	Is a tracepoint for debugging.
Patches 5-9 	Refactor existing khugepaged selftests to work with new
		memory types + new collapse tests.
Patch 10 	Adds a userfaultfd selftest mode to mimic a functional test
		of UFFDIO_REGISTER_MODE_MINOR+MADV_COLLAPSE live migration.
		(v4 note: "userfaultfd shmem" selftest is failing as of
		Sep 22 mm-unstable)

[1] https://lore.kernel.org/linux-mm/YyiK8YvVcrtZo0z3@google.com/
[2] https://lore.kernel.org/linux-mm/20220706235936.2197195-1-zokeefe@google.com/
[3] https://lore.kernel.org/linux-mm/YtBmhaiPHUTkJml8@google.com/
[4] https://lore.kernel.org/linux-mm/20220922222731.1124481-1-zokeefe@google.com/
[5] https://lore.kernel.org/linux-mm/20220922184651.1016461-1-zokeefe@google.com/


This patch (of 10):

Extend 'mm/thp: add flag to enforce sysfs THP in hugepage_vma_check()' to
shmem, allowing callers to ignore
/sys/kernel/transparent_hugepage/shmem_enabled and tmpfs huge= mount.

This is intended to be used by MADV_COLLAPSE, and the rationale is
analogous to the anon/file case: MADV_COLLAPSE is not coupled to
directives that advise the kernel's decisions on when THPs should be
considered eligible.  shmem/tmpfs always claims large folio support,
regardless of sysfs or mount options.

[shy828301@gmail.com: test shmem_huge_force explicitly]
  Link: https://lore.kernel.org/linux-mm/CAHbLzko3A5-TpS0BgBeKkx5cuOkWgLvWXQH=TdgW-baO4rPtdg@mail.gmail.com/
Link: https://lkml.kernel.org/r/20220922224046.1143204-1-zokeefe@google.com
Link: https://lkml.kernel.org/r/20220907144521.3115321-2-zokeefe@google.com
Link: https://lkml.kernel.org/r/20220922224046.1143204-2-zokeefe@google.com
Signed-off-by: Zach O'Keefe 
Reviewed-by: Yang Shi 
Cc: Axel Rasmussen 
Cc: Chris Kennelly 
Cc: David Hildenbrand 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: James Houghton 
Cc: "Kirill A. Shutemov" 
Cc: Matthew Wilcox 
Cc: Miaohe Lin 
Cc: Minchan Kim 
Cc: Pasha Tatashin 
Cc: Peter Xu 
Cc: Rongwei Wang 
Cc: SeongJae Park 
Cc: Song Liu 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

shmem: remove shmem_getpage()

2022-10-03T21:02:50+00:00

With all callers removed, remove this wrapper function.  The flags are now
mysteriously called SGP, but I think we can live with that.

Link: https://lkml.kernel.org/r/20220902194653.1739778-34-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton

shmem: add shmem_get_folio()

2022-10-03T21:02:49+00:00

With no remaining callers of shmem_getpage_gfp(), add shmem_get_folio()
and reimplement shmem_getpage() as a call to shmem_get_folio().

Link: https://lkml.kernel.org/r/20220902194653.1739778-25-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton