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Linus Torvalds c5c009e250 slab updates for 5.18
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Merge tag 'slab-for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

Pull slab updates from Vlastimil Babka:

 - A few non-trivial SLUB code cleanups, most notably a refactoring of
   deactivate_slab().

 - A bunch of trivial changes, such as removal of unused parameters,
   making stuff static, and employing helper functions.

* tag 'slab-for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab:
  mm: slub: Delete useless parameter of alloc_slab_page()
  mm: slab: Delete unused SLAB_DEACTIVATED flag
  mm/slub: remove forced_order parameter in calculate_sizes
  mm/slub: refactor deactivate_slab()
  mm/slub: limit number of node partial slabs only in cache creation
  mm/slub: use helper macro __ATTR_XX_MODE for SLAB_ATTR(_RO)
  mm/slab_common: use helper function is_power_of_2()
  mm/slob: make kmem_cache_boot static
2022-03-23 12:33:21 -07:00
Muchun Song 88f2ef73fd mm: introduce kmem_cache_alloc_lru
We currently allocate scope for every memcg to be able to tracked on
every superblock instantiated in the system, regardless of whether that
superblock is even accessible to that memcg.

These huge memcg counts come from container hosts where memcgs are
confined to just a small subset of the total number of superblocks that
instantiated at any given point in time.

For these systems with huge container counts, list_lru does not need the
capability of tracking every memcg on every superblock.  What it comes
down to is that adding the memcg to the list_lru at the first insert.
So introduce kmem_cache_alloc_lru to allocate objects and its list_lru.
In the later patch, we will convert all inode and dentry allocation from
kmem_cache_alloc to kmem_cache_alloc_lru.

Link: https://lkml.kernel.org/r/20220228122126.37293-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: Anna Schumaker <Anna.Schumaker@Netapp.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Fam Zheng <fam.zheng@bytedance.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kari Argillander <kari.argillander@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-22 15:57:03 -07:00
Vlastimil Babka 94fa31e99b Merge branch 'slab/for-5.18/cleanups' into slab/for-linus
Non-trivial SLUB code cleanups, notably refactoring of deactivate_slab().
2022-03-21 19:48:49 +01:00
Xiongwei Song a485e1dacd mm: slub: Delete useless parameter of alloc_slab_page()
The parameter @s is useless for alloc_slab_page(). It was added in 2014
by commit 5dfb417509 ("sl[au]b: charge slabs to kmemcg explicitly"). The
need for it was removed in 2020 by commit 1f3147b49d ("mm: slub: call
account_slab_page() after slab page initialization"). Let's delete it.

[willy@infradead.org: Added detailed history of @s]

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20220310140701.87908-3-sxwjean@me.com
2022-03-10 18:14:25 +01:00
Miaohe Lin ae44d81d50 mm/slub: remove forced_order parameter in calculate_sizes
Since commit 32a6f409b6 ("mm, slub: remove runtime allocation order
changes"), forced_order is always -1. Remove this unneeded parameter
to simplify the code.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20220309092036.50844-1-linmiaohe@huawei.com
2022-03-09 12:28:08 +01:00
Hyeonggon Yoo 6d3a16d09b mm/slub: refactor deactivate_slab()
Simplify deactivate_slab() by unlocking n->list_lock and retrying
cmpxchg_double() when cmpxchg_double() fails, and perform
add_{partial,full} only when it succeed.

Releasing and taking n->list_lock again here is not harmful as SLUB
avoids deactivating slabs as much as possible.

[ vbabka@suse.cz: perform add_{partial,full} when cmpxchg_double()
  succeed.

  count deactivating full slabs even if debugging flag is not set. ]

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20220307074057.902222-3-42.hyeyoo@gmail.com
2022-03-09 12:25:29 +01:00
Hyeonggon Yoo 5182f3c918 mm/slub: limit number of node partial slabs only in cache creation
SLUB sets number of minimum partial slabs for node (min_partial)
using set_min_partial(). SLUB holds at least min_partial slabs even if
they're empty to avoid excessive use of page allocator.

set_min_partial() limits value of min_partial limits value of
min_partial MIN_PARTIAL and MAX_PARTIAL. As set_min_partial() can be
called by min_partial_store() too, Only limit value of min_partial
in kmem_cache_open() so that it can be changed to value that a user wants.

[ rientjes@google.com: Fold set_min_partial() into its callers ]

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20220307074057.902222-2-42.hyeyoo@gmail.com
2022-03-09 12:25:18 +01:00
Lianjie Zhang d1d28bd9a0 mm/slub: use helper macro __ATTR_XX_MODE for SLAB_ATTR(_RO)
This allows more concise code, and VERIFY_OCTAL_PERMISSIONS() can help
validate any future change.

Signed-off-by: Lianjie Zhang <zhanglianjie@uniontech.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/20220306073818.15089-1-zhanglianjie@uniontech.com
2022-03-07 18:08:35 +01:00
Vlastimil Babka 9c01e9af17 mm/slub: Define struct slab fields for CONFIG_SLUB_CPU_PARTIAL only when enabled
The fields 'next' and 'slabs' are only used when CONFIG_SLUB_CPU_PARTIAL
is enabled. We can put their definition to #ifdef to prevent accidental
use when disabled.

Currenlty show_slab_objects() and slabs_cpu_partial_show() contain code
accessing the slabs field that's effectively dead with
CONFIG_SLUB_CPU_PARTIAL=n through the wrappers slub_percpu_partial() and
slub_percpu_partial_read_once(), but to prevent a compile error, we need
to hide all this code behind #ifdef.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
2022-01-06 12:26:53 +01:00
Matthew Wilcox (Oracle) 6e48a966df mm/kasan: Convert to struct folio and struct slab
KASAN accesses some slab related struct page fields so we need to
convert it to struct slab. Some places are a bit simplified thanks to
kasan_addr_to_slab() encapsulating the PageSlab flag check through
virt_to_slab().  When resolving object address to either a real slab or
a large kmalloc, use struct folio as the intermediate type for testing
the slab flag to avoid unnecessary implicit compound_head().

[ vbabka@suse.cz: use struct folio, adjust to differences in previous
  patches ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Tested-by: Hyeongogn Yoo <42.hyeyoo@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: <kasan-dev@googlegroups.com>
2022-01-06 12:26:14 +01:00
Vlastimil Babka 40f3bf0cb0 mm: Convert struct page to struct slab in functions used by other subsystems
KASAN, KFENCE and memcg interact with SLAB or SLUB internals through
functions nearest_obj(), obj_to_index() and objs_per_slab() that use
struct page as parameter. This patch converts it to struct slab
including all callers, through a coccinelle semantic patch.

// Options: --include-headers --no-includes --smpl-spacing include/linux/slab_def.h include/linux/slub_def.h mm/slab.h mm/kasan/*.c mm/kfence/kfence_test.c mm/memcontrol.c mm/slab.c mm/slub.c
// Note: needs coccinelle 1.1.1 to avoid breaking whitespace

@@
@@

-objs_per_slab_page(
+objs_per_slab(
 ...
 )
 { ... }

@@
@@

-objs_per_slab_page(
+objs_per_slab(
 ...
 )

@@
identifier fn =~ "obj_to_index|objs_per_slab";
@@

 fn(...,
-   const struct page *page
+   const struct slab *slab
    ,...)
 {
<...
(
- page_address(page)
+ slab_address(slab)
|
- page
+ slab
)
...>
 }

@@
identifier fn =~ "nearest_obj";
@@

 fn(...,
-   struct page *page
+   const struct slab *slab
    ,...)
 {
<...
(
- page_address(page)
+ slab_address(slab)
|
- page
+ slab
)
...>
 }

@@
identifier fn =~ "nearest_obj|obj_to_index|objs_per_slab";
expression E;
@@

 fn(...,
(
- slab_page(E)
+ E
|
- virt_to_page(E)
+ virt_to_slab(E)
|
- virt_to_head_page(E)
+ virt_to_slab(E)
|
- page
+ page_slab(page)
)
  ,...)

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Julia Lawall <julia.lawall@inria.fr>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: <kasan-dev@googlegroups.com>
Cc: <cgroups@vger.kernel.org>
2022-01-06 12:26:13 +01:00
Vlastimil Babka c2092c1206 mm/slub: Finish struct page to struct slab conversion
Update comments mentioning pages to mention slabs where appropriate.
Also some goto labels.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:26:02 +01:00
Vlastimil Babka bb192ed9aa mm/slub: Convert most struct page to struct slab by spatch
The majority of conversion from struct page to struct slab in SLUB
internals can be delegated to a coccinelle semantic patch. This includes
renaming of variables with 'page' in name to 'slab', and similar.

Big thanks to Julia Lawall and Luis Chamberlain for help with
coccinelle.

// Options: --include-headers --no-includes --smpl-spacing include/linux/slub_def.h mm/slub.c
// Note: needs coccinelle 1.1.1 to avoid breaking whitespace, and ocaml for the
// embedded script

// build list of functions to exclude from applying the next rule
@initialize:ocaml@
@@

let ok_function p =
  not (List.mem (List.hd p).current_element ["nearest_obj";"obj_to_index";"objs_per_slab_page";"__slab_lock";"__slab_unlock";"free_nonslab_page";"kmalloc_large_node"])

// convert the type from struct page to struct page in all functions except the
// list from previous rule
// this also affects struct kmem_cache_cpu, but that's ok
@@
position p : script:ocaml() { ok_function p };
@@

- struct page@p
+ struct slab

// in struct kmem_cache_cpu, change the name from page to slab
// the type was already converted by the previous rule
@@
@@

struct kmem_cache_cpu {
...
-struct slab *page;
+struct slab *slab;
...
}

// there are many places that use c->page which is now c->slab after the
// previous rule
@@
struct kmem_cache_cpu *c;
@@

-c->page
+c->slab

@@
@@

struct kmem_cache {
...
- unsigned int cpu_partial_pages;
+ unsigned int cpu_partial_slabs;
...
}

@@
struct kmem_cache *s;
@@

- s->cpu_partial_pages
+ s->cpu_partial_slabs

@@
@@

static void
- setup_page_debug(
+ setup_slab_debug(
 ...)
 {...}

@@
@@

- setup_page_debug(
+ setup_slab_debug(
 ...);

// for all functions (with exceptions), change any "struct slab *page"
// parameter to "struct slab *slab" in the signature, and generally all
// occurences of "page" to "slab" in the body - with some special cases.

@@
identifier fn !~ "free_nonslab_page|obj_to_index|objs_per_slab_page|nearest_obj";
@@
 fn(...,
-   struct slab *page
+   struct slab *slab
    ,...)
 {
<...
- page
+ slab
...>
 }

// similar to previous but the param is called partial_page
@@
identifier fn;
@@

 fn(...,
-   struct slab *partial_page
+   struct slab *partial_slab
    ,...)
 {
<...
- partial_page
+ partial_slab
...>
 }

// similar to previous but for functions that take pointer to struct page ptr
@@
identifier fn;
@@

 fn(...,
-   struct slab **ret_page
+   struct slab **ret_slab
    ,...)
 {
<...
- ret_page
+ ret_slab
...>
 }

// functions converted by previous rules that were temporarily called using
// slab_page(E) so we want to remove the wrapper now that they accept struct
// slab ptr directly
@@
identifier fn =~ "slab_free|do_slab_free";
expression E;
@@

 fn(...,
- slab_page(E)
+ E
  ,...)

// similar to previous but for another pattern
@@
identifier fn =~ "slab_pad_check|check_object";
@@

 fn(...,
- folio_page(folio, 0)
+ slab
  ,...)

// functions that were returning struct page ptr and now will return struct
// slab ptr, including slab_page() wrapper removal
@@
identifier fn =~ "allocate_slab|new_slab";
expression E;
@@

 static
-struct slab *
+struct slab *
 fn(...)
 {
<...
- slab_page(E)
+ E
...>
 }

// rename any former struct page * declarations
@@
@@

struct slab *
(
- page
+ slab
|
- partial_page
+ partial_slab
|
- oldpage
+ oldslab
)
;

// this has to be separate from previous rule as page and page2 appear at the
// same line
@@
@@

struct slab *
-page2
+slab2
;

// similar but with initial assignment
@@
expression E;
@@

struct slab *
(
- page
+ slab
|
- flush_page
+ flush_slab
|
- discard_page
+ slab_to_discard
|
- page_to_unfreeze
+ slab_to_unfreeze
)
= E;

// convert most of struct page to struct slab usage inside functions (with
// exceptions), including specific variable renames
@@
identifier fn !~ "nearest_obj|obj_to_index|objs_per_slab_page|__slab_(un)*lock|__free_slab|free_nonslab_page|kmalloc_large_node";
expression E;
@@

 fn(...)
 {
<...
(
- int pages;
+ int slabs;
|
- int pages = E;
+ int slabs = E;
|
- page
+ slab
|
- flush_page
+ flush_slab
|
- partial_page
+ partial_slab
|
- oldpage->pages
+ oldslab->slabs
|
- oldpage
+ oldslab
|
- unsigned int nr_pages;
+ unsigned int nr_slabs;
|
- nr_pages
+ nr_slabs
|
- unsigned int partial_pages = E;
+ unsigned int partial_slabs = E;
|
- partial_pages
+ partial_slabs
)
...>
 }

// this has to be split out from the previous rule so that lines containing
// multiple matching changes will be fully converted
@@
identifier fn !~ "nearest_obj|obj_to_index|objs_per_slab_page|__slab_(un)*lock|__free_slab|free_nonslab_page|kmalloc_large_node";
@@

 fn(...)
 {
<...
(
- slab->pages
+ slab->slabs
|
- pages
+ slabs
|
- page2
+ slab2
|
- discard_page
+ slab_to_discard
|
- page_to_unfreeze
+ slab_to_unfreeze
)
...>
 }

// after we simply changed all occurences of page to slab, some usages need
// adjustment for slab-specific functions, or use slab_page() wrapper
@@
identifier fn !~ "nearest_obj|obj_to_index|objs_per_slab_page|__slab_(un)*lock|__free_slab|free_nonslab_page|kmalloc_large_node";
@@

 fn(...)
 {
<...
(
- page_slab(slab)
+ slab
|
- kasan_poison_slab(slab)
+ kasan_poison_slab(slab_page(slab))
|
- page_address(slab)
+ slab_address(slab)
|
- page_size(slab)
+ slab_size(slab)
|
- PageSlab(slab)
+ folio_test_slab(slab_folio(slab))
|
- page_to_nid(slab)
+ slab_nid(slab)
|
- compound_order(slab)
+ slab_order(slab)
)
...>
 }

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Julia Lawall <julia.lawall@inria.fr>
Cc: Luis Chamberlain <mcgrof@kernel.org>
2022-01-06 12:26:02 +01:00
Matthew Wilcox (Oracle) 01b34d1631 mm/slub: Convert pfmemalloc_match() to take a struct slab
Preparatory for mass conversion. Use the new slab_test_pfmemalloc()
helper.  As it doesn't do VM_BUG_ON(!PageSlab()) we no longer need the
pfmemalloc_match_unsafe() variant.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
2022-01-06 12:26:02 +01:00
Vlastimil Babka 4020b4a226 mm/slub: Convert __free_slab() to use struct slab
__free_slab() is on the boundary of distinguishing struct slab and
struct page so start with struct slab but convert to folio for working
with flags and folio_page() to call functions that require struct page.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
2022-01-06 12:26:01 +01:00
Vlastimil Babka 45387b8c14 mm/slub: Convert alloc_slab_page() to return a struct slab
Preparatory, callers convert back to struct page for now.

Also move setting page flags to alloc_slab_page() where we still operate
on a struct page. This means the page->slab_cache pointer is now set
later than the PageSlab flag, which could theoretically confuse some pfn
walker assuming PageSlab means there would be a valid cache pointer. But
as the code had no barriers and used __set_bit() anyway, it could have
happened already, so there shouldn't be such a walker.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
2022-01-06 12:26:01 +01:00
Matthew Wilcox (Oracle) fb012e278d mm/slub: Convert print_page_info() to print_slab_info()
Improve the type safety and prepare for further conversion. For flags
access, convert to folio internally.

[ vbabka@suse.cz: access flags via folio_flags() ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
2022-01-06 12:26:01 +01:00
Vlastimil Babka 0393895b09 mm/slub: Convert __slab_lock() and __slab_unlock() to struct slab
These functions operate on the PG_locked page flag, but make them accept
struct slab to encapsulate this implementation detail.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:26:01 +01:00
Matthew Wilcox (Oracle) d835eef4fc mm/slub: Convert kfree() to use a struct slab
Convert kfree(), kmem_cache_free() and ___cache_free() to resolve object
addresses to struct slab, using folio as intermediate step where needed.
Keep passing the result as struct page for now in preparation for mass
conversion of internal functions.

[ vbabka@suse.cz: Use folio as intermediate step when checking for
  large kmalloc pages, and when freeing them - rename
  free_nonslab_page() to free_large_kmalloc() that takes struct folio ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:57 +01:00
Matthew Wilcox (Oracle) cc465c3b23 mm/slub: Convert detached_freelist to use a struct slab
This gives us a little bit of extra typesafety as we know that nobody
called virt_to_page() instead of virt_to_head_page().

[ vbabka@suse.cz: Use folio as intermediate step when filtering out
  large kmalloc pages ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:51 +01:00
Matthew Wilcox (Oracle) 0b3eb091d5 mm: Convert check_heap_object() to use struct slab
Ensure that we're not seeing a tail page inside __check_heap_object() by
converting to a slab instead of a page.  Take the opportunity to mark
the slab as const since we're not modifying it.  Also move the
declaration of __check_heap_object() to mm/slab.h so it's not available
to the wider kernel.

[ vbabka@suse.cz: in check_heap_object() only convert to struct slab for
  actual PageSlab pages; use folio as intermediate step instead of page ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:51 +01:00
Matthew Wilcox (Oracle) 7213230af5 mm: Use struct slab in kmem_obj_info()
All three implementations of slab support kmem_obj_info() which reports
details of an object allocated from the slab allocator.  By using the
slab type instead of the page type, we make it obvious that this can
only be called for slabs.

[ vbabka@suse.cz: also convert the related kmem_valid_obj() to folios ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:51 +01:00
Matthew Wilcox (Oracle) 0c24811b12 mm: Convert __ksize() to struct slab
In SLUB, use folios, and struct slab to access slab_cache field.
In SLOB, use folios to properly resolve pointers beyond
PAGE_SIZE offset of the object.

[ vbabka@suse.cz: use folios, and only convert folio_test_slab() == true
  folios to struct slab ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:51 +01:00
Matthew Wilcox (Oracle) b918653b4f mm: Convert [un]account_slab_page() to struct slab
Convert the parameter of these functions to struct slab instead of
struct page and drop _page from the names. For now their callers just
convert page to slab.

[ vbabka@suse.cz: replace existing functions instead of calling them ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:40 +01:00
Matthew Wilcox (Oracle) d122019bf0 mm: Split slab into its own type
Make struct slab independent of struct page. It still uses the
underlying memory in struct page for storing slab-specific data, but
slab and slub can now be weaned off using struct page directly.  Some of
the wrapper functions (slab_address() and slab_order()) still need to
cast to struct folio, but this is a significant disentanglement.

[ vbabka@suse.cz: Rebase on folios, use folio instead of page where
  possible.

  Do not duplicate flags field in struct slab, instead make the related
  accessors go through slab_folio(). For testing pfmemalloc use the
  folio_*_active flag accessors directly so the PageSlabPfmemalloc
  wrappers can be removed later.

  Make folio_slab() expect only folio_test_slab() == true folios and
  virt_to_slab() return NULL when folio_test_slab() == false.

  Move struct slab to mm/slab.h.

  Don't represent with struct slab pages that are not true slab pages,
  but just a compound page obtained directly rom page allocator (with
  large kmalloc() for SLUB and SLOB). ]

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:40 +01:00
Vlastimil Babka ae16d059f8 mm/slub: Make object_err() static
There are no callers outside of mm/slub.c anymore.

Move freelist_corrupted() that calls object_err() to avoid a need for
forward declaration.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Roman Gushchin <guro@fb.com>
2022-01-06 12:25:40 +01:00
Gerald Schaefer 005a79e5c2 mm/slub: fix endianness bug for alloc/free_traces attributes
On big-endian s390, the alloc/free_traces attributes produce endless
output, because of always 0 idx in slab_debugfs_show().

idx is de-referenced from *v, which points to a loff_t value, with

    unsigned int idx = *(unsigned int *)v;

This will only give the upper 32 bits on big-endian, which remain 0.

Instead of only fixing this de-reference, during discussion it seemed
more appropriate to change the seq_ops so that they use an explicit
iterator in private loc_track struct.

This patch adds idx to loc_track, which will also fix the endianness
bug.

Link: https://lore.kernel.org/r/20211117193932.4049412-1-gerald.schaefer@linux.ibm.com
Link: https://lkml.kernel.org/r/20211126171848.17534-1-gerald.schaefer@linux.ibm.com
Fixes: 64dd68497b ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reported-by: Steffen Maier <maier@linux.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Faiyaz Mohammed <faiyazm@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-12-10 17:10:56 -08:00
Yunfeng Ye 9a543f007b mm: emit the "free" trace report before freeing memory in kmem_cache_free()
After the memory is freed, it can be immediately allocated by other
CPUs, before the "free" trace report has been emitted.  This causes
inaccurate traces.

For example, if the following sequence of events occurs:

    CPU 0                 CPU 1

  (1) alloc xxxxxx
  (2) free  xxxxxx
                         (3) alloc xxxxxx
                         (4) free  xxxxxx

Then they will be inaccurately reported via tracing, so that they appear
to have happened in this order:

    CPU 0                 CPU 1

  (1) alloc xxxxxx
                         (2) alloc xxxxxx
  (3) free  xxxxxx
                         (4) free  xxxxxx

This makes it look like CPU 1 somehow managed to allocate memory that
CPU 0 still had allocated for itself.

In order to avoid this, emit the "free xxxxxx" tracing report just
before the actual call to free the memory, instead of just after it.

Link: https://lkml.kernel.org/r/374eb75d-7404-8721-4e1e-65b0e5b17279@huawei.com
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-20 10:35:54 -08:00
Linus Torvalds 512b7931ad Merge branch 'akpm' (patches from Andrew)
Merge misc updates from Andrew Morton:
 "257 patches.

  Subsystems affected by this patch series: scripts, ocfs2, vfs, and
  mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache,
  gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc,
  pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools,
  memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm,
  vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram,
  cleanups, kfence, and damon)"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (257 commits)
  mm/damon: remove return value from before_terminate callback
  mm/damon: fix a few spelling mistakes in comments and a pr_debug message
  mm/damon: simplify stop mechanism
  Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions
  Docs/admin-guide/mm/damon/start: simplify the content
  Docs/admin-guide/mm/damon/start: fix a wrong link
  Docs/admin-guide/mm/damon/start: fix wrong example commands
  mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on
  mm/damon: remove unnecessary variable initialization
  Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM
  mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)
  selftests/damon: support watermarks
  mm/damon/dbgfs: support watermarks
  mm/damon/schemes: activate schemes based on a watermarks mechanism
  tools/selftests/damon: update for regions prioritization of schemes
  mm/damon/dbgfs: support prioritization weights
  mm/damon/vaddr,paddr: support pageout prioritization
  mm/damon/schemes: prioritize regions within the quotas
  mm/damon/selftests: support schemes quotas
  mm/damon/dbgfs: support quotas of schemes
  ...
2021-11-06 14:08:17 -07:00
Stephen Kitt 53944f171a mm: remove HARDENED_USERCOPY_FALLBACK
This has served its purpose and is no longer used.  All usercopy
violations appear to have been handled by now, any remaining instances
(or new bugs) will cause copies to be rejected.

This isn't a direct revert of commit 2d891fbc3b ("usercopy: Allow
strict enforcement of whitelists"); since usercopy_fallback is
effectively 0, the fallback handling is removed too.

This also removes the usercopy_fallback module parameter on slab_common.

Link: https://github.com/KSPP/linux/issues/153
Link: https://lkml.kernel.org/r/20210921061149.1091163-1-steve@sk2.org
Signed-off-by: Stephen Kitt <steve@sk2.org>
Suggested-by: Kees Cook <keescook@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>	[defconfig change]
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E . Hallyn" <serge@hallyn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:43 -07:00
Hyeonggon Yoo 04b4b00613 mm, slub: use prefetchw instead of prefetch
Commit 0ad9500e16 ("slub: prefetch next freelist pointer in
slab_alloc()") introduced prefetch_freepointer() because when other
cpu(s) freed objects into a page that current cpu owns, the freelist
link is hot on cpu(s) which freed objects and possibly very cold on
current cpu.

But if freelist link chain is hot on cpu(s) which freed objects, it's
better to invalidate that chain because they're not going to access
again within a short time.

So use prefetchw instead of prefetch.  On supported architectures like
x86 and arm, it invalidates other copied instances of a cache line when
prefetching it.

Before:

Time: 91.677

 Performance counter stats for 'hackbench -g 100 -l 10000':
        1462938.07 msec cpu-clock                 #   15.908 CPUs utilized
          18072550      context-switches          #   12.354 K/sec
           1018814      cpu-migrations            #  696.416 /sec
            104558      page-faults               #   71.471 /sec
     1580035699271      cycles                    #    1.080 GHz                      (54.51%)
     2003670016013      instructions              #    1.27  insn per cycle           (54.31%)
        5702204863      branch-misses                                                 (54.28%)
      643368500985      cache-references          #  439.778 M/sec                    (54.26%)
       18475582235      cache-misses              #    2.872 % of all cache refs      (54.28%)
      642206796636      L1-dcache-loads           #  438.984 M/sec                    (46.87%)
       18215813147      L1-dcache-load-misses     #    2.84% of all L1-dcache accesses  (46.83%)
      653842996501      dTLB-loads                #  446.938 M/sec                    (46.63%)
        3227179675      dTLB-load-misses          #    0.49% of all dTLB cache accesses  (46.85%)
      537531951350      iTLB-loads                #  367.433 M/sec                    (54.33%)
         114750630      iTLB-load-misses          #    0.02% of all iTLB cache accesses  (54.37%)
      630135543177      L1-icache-loads           #  430.733 M/sec                    (46.80%)
       22923237620      L1-icache-load-misses     #    3.64% of all L1-icache accesses  (46.76%)

      91.964452802 seconds time elapsed

      43.416742000 seconds user
    1422.441123000 seconds sys

After:

Time: 90.220

 Performance counter stats for 'hackbench -g 100 -l 10000':
        1437418.48 msec cpu-clock                 #   15.880 CPUs utilized
          17694068      context-switches          #   12.310 K/sec
            958257      cpu-migrations            #  666.651 /sec
            100604      page-faults               #   69.989 /sec
     1583259429428      cycles                    #    1.101 GHz                      (54.57%)
     2004002484935      instructions              #    1.27  insn per cycle           (54.37%)
        5594202389      branch-misses                                                 (54.36%)
      643113574524      cache-references          #  447.409 M/sec                    (54.39%)
       18233791870      cache-misses              #    2.835 % of all cache refs      (54.37%)
      640205852062      L1-dcache-loads           #  445.386 M/sec                    (46.75%)
       17968160377      L1-dcache-load-misses     #    2.81% of all L1-dcache accesses  (46.79%)
      651747432274      dTLB-loads                #  453.415 M/sec                    (46.59%)
        3127124271      dTLB-load-misses          #    0.48% of all dTLB cache accesses  (46.75%)
      535395273064      iTLB-loads                #  372.470 M/sec                    (54.38%)
         113500056      iTLB-load-misses          #    0.02% of all iTLB cache accesses  (54.35%)
      628871845924      L1-icache-loads           #  437.501 M/sec                    (46.80%)
       22585641203      L1-icache-load-misses     #    3.59% of all L1-icache accesses  (46.79%)

      90.514819303 seconds time elapsed

      43.877656000 seconds user
    1397.176001000 seconds sys

Link: https://lkml.org/lkml/2021/10/8/598=20
Link: https://lkml.kernel.org/r/20211011144331.70084-1-42.hyeyoo@gmail.com
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:33 -07:00
Vlastimil Babka 23e98ad1ce mm/slub: increase default cpu partial list sizes
The defaults are determined based on object size and can go up to 30 for
objects smaller than 256 bytes.  Before the previous patch changed the
accounting, this could have made cpu partial list contain up to 30
pages.  After that patch, only up to 2 pages with default allocation
order.

Very short lists limit the usefulness of the whole concept of cpu
partial lists, so this patch aims at a more reasonable default under the
new accounting.  The defaults are quadrupled, except for object size >=
PAGE_SIZE where it's doubled.  This makes the lists grow up to 10 pages
in practice.

A quick test of booting a kernel under virtme with 4GB RAM and 8 vcpus
shows the following slab memory usage after boot:

Before previous patch (using page->pobjects):
  Slab:              36732 kB
  SReclaimable:      14836 kB
  SUnreclaim:        21896 kB

After previous patch (using page->pages):
  Slab:              34720 kB
  SReclaimable:      13716 kB
  SUnreclaim:        21004 kB

After this patch (using page->pages, higher defaults):
  Slab:              35252 kB
  SReclaimable:      13944 kB
  SUnreclaim:        21308 kB

In the same setup, I also ran 5 times:

    hackbench -l 16000 -g 16

Differences in time were in the noise, we can compare slub stats as
given by slabinfo -r skbuff_head_cache (the other cache heavily used by
hackbench, kmalloc-cg-512 looks similar).  Negligible stats left out for
brevity.

Before previous patch (using page->pobjects):

  Objects: 1408, Memory Total:  401408 Used :  304128

  Slab Perf Counter       Alloc     Free %Al %Fr
  --------------------------------------------------
  Fastpath             469952498  5946606  91   1
  Slowpath             42053573 506059465   8  98
  Page Alloc              41093    41044   0   0
  Add partial                18 21229327   0   4
  Remove partial       20039522    36051   3   0
  Cpu partial list      4686640 24767229   0   4
  RemoteObj/SlabFrozen       16 124027841   0  24
  Total                512006071 512006071
  Flushes       18

  Slab Deactivation             Occurrences %
  -------------------------------------------------
  Slab empty                       4993    0%
  Deactivation bypass           24767229   99%
  Refilled from foreign frees   21972674   88%

After previous patch (using page->pages):

  Objects: 480, Memory Total:  131072 Used :  103680

  Slab Perf Counter       Alloc     Free %Al %Fr
  --------------------------------------------------
  Fastpath             473016294  5405653  92   1
  Slowpath             38989777 506600418   7  98
  Page Alloc              32717    32701   0   0
  Add partial                 3 22749164   0   4
  Remove partial       11371127    32474   2   0
  Cpu partial list     11686226 23090059   2   4
  RemoteObj/SlabFrozen        2 67541803   0  13
  Total                512006071 512006071
  Flushes        3

  Slab Deactivation             Occurrences %
  -------------------------------------------------
  Slab empty                        227    0%
  Deactivation bypass           23090059   99%
  Refilled from foreign frees   27585695  119%

After this patch (using page->pages, higher defaults):

  Objects: 896, Memory Total:  229376 Used :  193536

  Slab Perf Counter       Alloc     Free %Al %Fr
  --------------------------------------------------
  Fastpath             473799295  4980278  92   0
  Slowpath             38206776 507025793   7  99
  Page Alloc              32295    32267   0   0
  Add partial                11 23291143   0   4
  Remove partial        5815764    31278   1   0
  Cpu partial list     18119280 23967320   3   4
  RemoteObj/SlabFrozen       10 76974794   0  15
  Total                512006071 512006071
  Flushes       11

  Slab Deactivation             Occurrences %
  -------------------------------------------------
  Slab empty                        989    0%
  Deactivation bypass           23967320   99%
  Refilled from foreign frees   32358473  135%

As expected, memory usage dropped significantly with change of
accounting, increasing the defaults increased it, but not as much.  The
number of page allocation/frees dropped significantly with the new
accounting, but didn't increase with the higher defaults.
Interestingly, the number of fasthpath allocations increased, as well as
allocations from the cpu partial list, even though it's shorter.

Link: https://lkml.kernel.org/r/20211012134651.11258-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:32 -07:00
Vlastimil Babka b47291ef02 mm, slub: change percpu partial accounting from objects to pages
With CONFIG_SLUB_CPU_PARTIAL enabled, SLUB keeps a percpu list of
partial slabs that can be promoted to cpu slab when the previous one is
depleted, without accessing the shared partial list.  A slab can be
added to this list by 1) refill of an empty list from get_partial_node()
- once we really have to access the shared partial list, we acquire
multiple slabs to amortize the cost of locking, and 2) first free to a
previously full slab - instead of putting the slab on a shared partial
list, we can more cheaply freeze it and put it on the per-cpu list.

To control how large a percpu partial list can grow for a kmem cache,
set_cpu_partial() calculates a target number of free objects on each
cpu's percpu partial list, and this can be also set by the sysfs file
cpu_partial.

However, the tracking of actual number of objects is imprecise, in order
to limit overhead from cpu X freeing an objects to a slab on percpu
partial list of cpu Y.  Basically, the percpu partial slabs form a
single linked list, and when we add a new slab to the list with current
head "oldpage", we set in the struct page of the slab we're adding:

    page->pages = oldpage->pages + 1; // this is precise
    page->pobjects = oldpage->pobjects + (page->objects - page->inuse);
    page->next = oldpage;

Thus the real number of free objects in the slab (objects - inuse) is
only determined at the moment of adding the slab to the percpu partial
list, and further freeing doesn't update the pobjects counter nor
propagate it to the current list head.  As Jann reports [1], this can
easily lead to large inaccuracies, where the target number of objects
(up to 30 by default) can translate to the same number of (empty) slab
pages on the list.  In case 2) above, we put a slab with 1 free object
on the list, thus only increase page->pobjects by 1, even if there are
subsequent frees on the same slab.  Jann has noticed this in practice
and so did we [2] when investigating significant increase of kmemcg
usage after switching from SLAB to SLUB.

While this is no longer a problem in kmemcg context thanks to the
accounting rewrite in 5.9, the memory waste is still not ideal and it's
questionable whether it makes sense to perform free object count based
control when object counts can easily become so much inaccurate.  So
this patch converts the accounting to be based on number of pages only
(which is precise) and removes the page->pobjects field completely.
This is also ultimately simpler.

To retain the existing set_cpu_partial() heuristic, first calculate the
target number of objects as previously, but then convert it to target
number of pages by assuming the pages will be half-filled on average.
This assumption might obviously also be inaccurate in practice, but
cannot degrade to actual number of pages being equal to the target
number of objects.

We could also skip the intermediate step with target number of objects
and rewrite the heuristic in terms of pages.  However we still have the
sysfs file cpu_partial which uses number of objects and could break
existing users if it suddenly becomes number of pages, so this patch
doesn't do that.

In practice, after this patch the heuristics limit the size of percpu
partial list up to 2 pages.  In case of a reported regression (which
would mean some workload has benefited from the previous imprecise
object based counting), we can tune the heuristics to get a better
compromise within the new scheme, while still avoid the unexpectedly
long percpu partial lists.

[1] https://lore.kernel.org/linux-mm/CAG48ez2Qx5K1Cab-m8BdSibp6wLTip6ro4=-umR7BLsEgjEYzA@mail.gmail.com/
[2] https://lore.kernel.org/all/2f0f46e8-2535-410a-1859-e9cfa4e57c18@suse.cz/

==========
Evaluation
==========

Mel was kind enough to run v1 through mmtests machinery for netperf
(localhost) and hackbench and, for most significant results see below.
So there are some apparent regressions, especially with hackbench, which
I think ultimately boils down to having shorter percpu partial lists on
average and some benchmarks benefiting from longer ones.  Monitoring
slab usage also indicated less memory usage by slab.  Based on that, the
following patch will bump the defaults to allow longer percpu partial
lists than after this patch.

However the goal is certainly not such that we would limit the percpu
partial lists to 30 pages just because previously a specific alloc/free
pattern could lead to the limit of 30 objects translate to a limit to 30
pages - that would make little sense.  This is a correctness patch, and
if a workload benefits from larger lists, the sysfs tuning knobs are
still there to allow that.

Netperf

  2-socket Intel(R) Xeon(R) Gold 5218R CPU @ 2.10GHz (20 cores, 40 threads per socket), 384GB RAM
  TCP-RR:
    hmean before 127045.79 after 121092.94 (-4.69%, worse)
    stddev before  2634.37 after   1254.08
  UDP-RR:
    hmean before 166985.45 after 160668.94 ( -3.78%, worse)
    stddev before 4059.69 after 1943.63

  2-socket Intel(R) Xeon(R) CPU E5-2698 v4 @ 2.20GHz (20 cores, 40 threads per socket), 512GB RAM
  TCP-RR:
    hmean before 84173.25 after 76914.72 ( -8.62%, worse)
  UDP-RR:
    hmean before 93571.12 after 96428.69 ( 3.05%, better)
    stddev before 23118.54 after 16828.14

  2-socket Intel(R) Xeon(R) CPU E5-2670 v3 @ 2.30GHz (12 cores, 24 threads per socket), 64GB RAM
  TCP-RR:
    hmean before 49984.92 after 48922.27 ( -2.13%, worse)
    stddev before 6248.15 after 4740.51
  UDP-RR:
    hmean before 61854.31 after 68761.81 ( 11.17%, better)
    stddev before 4093.54 after 5898.91

  other machines - within 2%

Hackbench

  (results before and after the patch, negative % means worse)

  2-socket AMD EPYC 7713 (64 cores, 128 threads per core), 256GB RAM
  hackbench-process-sockets
  Amean 	1 	0.5380	0.5583	( -3.78%)
  Amean 	4 	0.7510	0.8150	( -8.52%)
  Amean 	7 	0.7930	0.9533	( -20.22%)
  Amean 	12 	0.7853	1.1313	( -44.06%)
  Amean 	21 	1.1520	1.4993	( -30.15%)
  Amean 	30 	1.6223	1.9237	( -18.57%)
  Amean 	48 	2.6767	2.9903	( -11.72%)
  Amean 	79 	4.0257	5.1150	( -27.06%)
  Amean 	110	5.5193	7.4720	( -35.38%)
  Amean 	141	7.2207	9.9840	( -38.27%)
  Amean 	172	8.4770	12.1963	( -43.88%)
  Amean 	203	9.6473	14.3137	( -48.37%)
  Amean 	234	11.3960	18.7917	( -64.90%)
  Amean 	265	13.9627	22.4607	( -60.86%)
  Amean 	296	14.9163	26.0483	( -74.63%)

  hackbench-thread-sockets
  Amean 	1 	0.5597	0.5877	( -5.00%)
  Amean 	4 	0.7913	0.8960	( -13.23%)
  Amean 	7 	0.8190	1.0017	( -22.30%)
  Amean 	12 	0.9560	1.1727	( -22.66%)
  Amean 	21 	1.7587	1.5660	( 10.96%)
  Amean 	30 	2.4477	1.9807	( 19.08%)
  Amean 	48 	3.4573	3.0630	( 11.41%)
  Amean 	79 	4.7903	5.1733	( -8.00%)
  Amean 	110	6.1370	7.4220	( -20.94%)
  Amean 	141	7.5777	9.2617	( -22.22%)
  Amean 	172	9.2280	11.0907	( -20.18%)
  Amean 	203	10.2793	13.3470	( -29.84%)
  Amean 	234	11.2410	17.1070	( -52.18%)
  Amean 	265	12.5970	23.3323	( -85.22%)
  Amean 	296	17.1540	24.2857	( -41.57%)

  2-socket Intel(R) Xeon(R) Gold 5218R CPU @ 2.10GHz (20 cores, 40 threads
  per socket), 384GB RAM
  hackbench-process-sockets
  Amean 	1 	0.5760	0.4793	( 16.78%)
  Amean 	4 	0.9430	0.9707	( -2.93%)
  Amean 	7 	1.5517	1.8843	( -21.44%)
  Amean 	12 	2.4903	2.7267	( -9.49%)
  Amean 	21 	3.9560	4.2877	( -8.38%)
  Amean 	30 	5.4613	5.8343	( -6.83%)
  Amean 	48 	8.5337	9.2937	( -8.91%)
  Amean 	79 	14.0670	15.2630	( -8.50%)
  Amean 	110	19.2253	21.2467	( -10.51%)
  Amean 	141	23.7557	25.8550	( -8.84%)
  Amean 	172	28.4407	29.7603	( -4.64%)
  Amean 	203	33.3407	33.9927	( -1.96%)
  Amean 	234	38.3633	39.1150	( -1.96%)
  Amean 	265	43.4420	43.8470	( -0.93%)
  Amean 	296	48.3680	48.9300	( -1.16%)

  hackbench-thread-sockets
  Amean 	1 	0.6080	0.6493	( -6.80%)
  Amean 	4 	1.0000	1.0513	( -5.13%)
  Amean 	7 	1.6607	2.0260	( -22.00%)
  Amean 	12 	2.7637	2.9273	( -5.92%)
  Amean 	21 	5.0613	4.5153	( 10.79%)
  Amean 	30 	6.3340	6.1140	( 3.47%)
  Amean 	48 	9.0567	9.5577	( -5.53%)
  Amean 	79 	14.5657	15.7983	( -8.46%)
  Amean 	110	19.6213	21.6333	( -10.25%)
  Amean 	141	24.1563	26.2697	( -8.75%)
  Amean 	172	28.9687	30.2187	( -4.32%)
  Amean 	203	33.9763	34.6970	( -2.12%)
  Amean 	234	38.8647	39.3207	( -1.17%)
  Amean 	265	44.0813	44.1507	( -0.16%)
  Amean 	296	49.2040	49.4330	( -0.47%)

  2-socket Intel(R) Xeon(R) CPU E5-2698 v4 @ 2.20GHz (20 cores, 40 threads
  per socket), 512GB RAM
  hackbench-process-sockets
  Amean 	1 	0.5027	0.5017	( 0.20%)
  Amean 	4 	1.1053	1.2033	( -8.87%)
  Amean 	7 	1.8760	2.1820	( -16.31%)
  Amean 	12 	2.9053	3.1810	( -9.49%)
  Amean 	21 	4.6777	4.9920	( -6.72%)
  Amean 	30 	6.5180	6.7827	( -4.06%)
  Amean 	48 	10.0710	10.5227	( -4.48%)
  Amean 	79 	16.4250	17.5053	( -6.58%)
  Amean 	110	22.6203	24.4617	( -8.14%)
  Amean 	141	28.0967	31.0363	( -10.46%)
  Amean 	172	34.4030	36.9233	( -7.33%)
  Amean 	203	40.5933	43.0850	( -6.14%)
  Amean 	234	46.6477	48.7220	( -4.45%)
  Amean 	265	53.0530	53.9597	( -1.71%)
  Amean 	296	59.2760	59.9213	( -1.09%)

  hackbench-thread-sockets
  Amean 	1 	0.5363	0.5330	( 0.62%)
  Amean 	4 	1.1647	1.2157	( -4.38%)
  Amean 	7 	1.9237	2.2833	( -18.70%)
  Amean 	12 	2.9943	3.3110	( -10.58%)
  Amean 	21 	4.9987	5.1880	( -3.79%)
  Amean 	30 	6.7583	7.0043	( -3.64%)
  Amean 	48 	10.4547	10.8353	( -3.64%)
  Amean 	79 	16.6707	17.6790	( -6.05%)
  Amean 	110	22.8207	24.4403	( -7.10%)
  Amean 	141	28.7090	31.0533	( -8.17%)
  Amean 	172	34.9387	36.8260	( -5.40%)
  Amean 	203	41.1567	43.0450	( -4.59%)
  Amean 	234	47.3790	48.5307	( -2.43%)
  Amean 	265	53.9543	54.6987	( -1.38%)
  Amean 	296	60.0820	60.2163	( -0.22%)

  1-socket Intel(R) Xeon(R) CPU E3-1240 v5 @ 3.50GHz (4 cores, 8 threads),
  32 GB RAM
  hackbench-process-sockets
  Amean 	1 	1.4760	1.5773	( -6.87%)
  Amean 	3 	3.9370	4.0910	( -3.91%)
  Amean 	5 	6.6797	6.9357	( -3.83%)
  Amean 	7 	9.3367	9.7150	( -4.05%)
  Amean 	12	15.7627	16.1400	( -2.39%)
  Amean 	18	23.5360	23.6890	( -0.65%)
  Amean 	24	31.0663	31.3137	( -0.80%)
  Amean 	30	38.7283	39.0037	( -0.71%)
  Amean 	32	41.3417	41.6097	( -0.65%)

  hackbench-thread-sockets
  Amean 	1 	1.5250	1.6043	( -5.20%)
  Amean 	3 	4.0897	4.2603	( -4.17%)
  Amean 	5 	6.7760	7.0933	( -4.68%)
  Amean 	7 	9.4817	9.9157	( -4.58%)
  Amean 	12	15.9610	16.3937	( -2.71%)
  Amean 	18	23.9543	24.3417	( -1.62%)
  Amean 	24	31.4400	31.7217	( -0.90%)
  Amean 	30	39.2457	39.5467	( -0.77%)
  Amean 	32	41.8267	42.1230	( -0.71%)

  2-socket Intel(R) Xeon(R) CPU E5-2670 v3 @ 2.30GHz (12 cores, 24 threads
  per socket), 64GB RAM
  hackbench-process-sockets
  Amean 	1 	1.0347	1.0880	( -5.15%)
  Amean 	4 	1.7267	1.8527	( -7.30%)
  Amean 	7 	2.6707	2.8110	( -5.25%)
  Amean 	12 	4.1617	4.3383	( -4.25%)
  Amean 	21 	7.0070	7.2600	( -3.61%)
  Amean 	30 	9.9187	10.2397	( -3.24%)
  Amean 	48 	15.6710	16.3923	( -4.60%)
  Amean 	79 	24.7743	26.1247	( -5.45%)
  Amean 	110	34.3000	35.9307	( -4.75%)
  Amean 	141	44.2043	44.8010	( -1.35%)
  Amean 	172	54.2430	54.7260	( -0.89%)
  Amean 	192	60.6557	60.9777	( -0.53%)

  hackbench-thread-sockets
  Amean 	1 	1.0610	1.1353	( -7.01%)
  Amean 	4 	1.7543	1.9140	( -9.10%)
  Amean 	7 	2.7840	2.9573	( -6.23%)
  Amean 	12 	4.3813	4.4937	( -2.56%)
  Amean 	21 	7.3460	7.5350	( -2.57%)
  Amean 	30 	10.2313	10.5190	( -2.81%)
  Amean 	48 	15.9700	16.5940	( -3.91%)
  Amean 	79 	25.3973	26.6637	( -4.99%)
  Amean 	110	35.1087	36.4797	( -3.91%)
  Amean 	141	45.8220	46.3053	( -1.05%)
  Amean 	172	55.4917	55.7320	( -0.43%)
  Amean 	192	62.7490	62.5410	( 0.33%)

Link: https://lkml.kernel.org/r/20211012134651.11258-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Jann Horn <jannh@google.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:32 -07:00
Kefeng Wang d0fe47c641 slub: add back check for free nonslab objects
After commit f227f0faf6 ("slub: fix unreclaimable slab stat for bulk
free"), the check for free nonslab page is replaced by VM_BUG_ON_PAGE,
which only check with CONFIG_DEBUG_VM enabled, but this config may
impact performance, so it only for debug.

Commit 0937502af7 ("slub: Add check for kfree() of non slab objects.")
add the ability, which should be needed in any configs to catch the
invalid free, they even could be potential issue, eg, memory corruption,
use after free and double free, so replace VM_BUG_ON_PAGE to
WARN_ON_ONCE, add object address printing to help use to debug the
issue.

Link: https://lkml.kernel.org/r/20210930070214.61499-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rienjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-11-06 13:30:32 -07:00
Linus Torvalds 0aaa58eca6 printk changes for 5.16
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Merge tag 'printk-for-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Extend %pGp print format to print hex value of the page flags

 - Use kvmalloc instead of kmalloc to allocate devkmsg buffers

 - Misc cleanup and warning fixes

* tag 'printk-for-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  vsprintf: Update %pGp documentation about that it prints hex value
  lib/vsprintf.c: Amend static asserts for format specifier flags
  vsprintf: Make %pGp print the hex value
  test_printf: Append strings more efficiently
  test_printf: Remove custom appending of '|'
  test_printf: Remove separate page_flags variable
  test_printf: Make pft array const
  ia64: don't do IA64_CMPXCHG_DEBUG without CONFIG_PRINTK
  printk: use gnu_printf format attribute for printk_sprint()
  printk: avoid -Wsometimes-uninitialized warning
  printk: use kvmalloc instead of kmalloc for devkmsg_user
2021-11-02 10:53:45 -07:00
Matthew Wilcox (Oracle) 23efd0804c vsprintf: Make %pGp print the hex value
All existing users of %pGp want the hex value as well as the decoded
flag names.  This looks awkward (passing the same parameter to printf
twice), so move that functionality into the core.  If we want, we
can make that optional with flag arguments to %pGp in the future.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211019142621.2810043-6-willy@infradead.org
2021-10-27 13:40:14 +02:00
Miaohe Lin 3ddd60268c mm, slub: fix incorrect memcg slab count for bulk free
kmem_cache_free_bulk() will call memcg_slab_free_hook() for all objects
when doing bulk free.  So we shouldn't call memcg_slab_free_hook() again
for bulk free to avoid incorrect memcg slab count.

Link: https://lkml.kernel.org/r/20210916123920.48704-6-linmiaohe@huawei.com
Fixes: d1b2cf6cb8 ("mm: memcg/slab: uncharge during kmem_cache_free_bulk()")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Faiyaz Mohammed <faiyazm@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-10-18 20:22:03 -10:00
Miaohe Lin 67823a5444 mm, slub: fix potential use-after-free in slab_debugfs_fops
When sysfs_slab_add failed, we shouldn't call debugfs_slab_add() for s
because s will be freed soon.  And slab_debugfs_fops will use s later
leading to a use-after-free.

Link: https://lkml.kernel.org/r/20210916123920.48704-5-linmiaohe@huawei.com
Fixes: 64dd68497b ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Faiyaz Mohammed <faiyazm@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-10-18 20:22:03 -10:00
Miaohe Lin 9037c57681 mm, slub: fix potential memoryleak in kmem_cache_open()
In error path, the random_seq of slub cache might be leaked.  Fix this
by using __kmem_cache_release() to release all the relevant resources.

Link: https://lkml.kernel.org/r/20210916123920.48704-4-linmiaohe@huawei.com
Fixes: 210e7a43fa ("mm: SLUB freelist randomization")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Faiyaz Mohammed <faiyazm@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-10-18 20:22:03 -10:00
Miaohe Lin 899447f669 mm, slub: fix mismatch between reconstructed freelist depth and cnt
If object's reuse is delayed, it will be excluded from the reconstructed
freelist.  But we forgot to adjust the cnt accordingly.  So there will
be a mismatch between reconstructed freelist depth and cnt.  This will
lead to free_debug_processing() complaining about freelist count or a
incorrect slub inuse count.

Link: https://lkml.kernel.org/r/20210916123920.48704-3-linmiaohe@huawei.com
Fixes: c3895391df ("kasan, slub: fix handling of kasan_slab_free hook")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Faiyaz Mohammed <faiyazm@codeaurora.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-10-18 20:22:03 -10:00
Miaohe Lin 2127d22509 mm, slub: fix two bugs in slab_debug_trace_open()
Patch series "Fixups for slub".

This series contains various bug fixes for slub.  We fix memoryleak,
use-afer-free, NULL pointer dereferencing and so on in slub.  More
details can be found in the respective changelogs.

This patch (of 5):

It's possible that __seq_open_private() will return NULL.  So we should
check it before using lest dereferencing NULL pointer.  And in error
paths, we forgot to release private buffer via seq_release_private().
Memory will leak in these paths.

Link: https://lkml.kernel.org/r/20210916123920.48704-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210916123920.48704-2-linmiaohe@huawei.com
Fixes: 64dd68497b ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Faiyaz Mohammed <faiyazm@codeaurora.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-10-18 20:22:03 -10:00
Vlastimil Babka bd0e7491a9 mm, slub: convert kmem_cpu_slab protection to local_lock
Embed local_lock into struct kmem_cpu_slab and use the irq-safe versions of
local_lock instead of plain local_irq_save/restore. On !PREEMPT_RT that's
equivalent, with better lockdep visibility. On PREEMPT_RT that means better
preemption.

However, the cost on PREEMPT_RT is the loss of lockless fast paths which only
work with cpu freelist. Those are designed to detect and recover from being
preempted by other conflicting operations (both fast or slow path), but the
slow path operations assume they cannot be preempted by a fast path operation,
which is guaranteed naturally with disabled irqs. With local locks on
PREEMPT_RT, the fast paths now also need to take the local lock to avoid races.

In the allocation fastpath slab_alloc_node() we can just defer to the slowpath
__slab_alloc() which also works with cpu freelist, but under the local lock.
In the free fastpath do_slab_free() we have to add a new local lock protected
version of freeing to the cpu freelist, as the existing slowpath only works
with the page freelist.

Also update the comment about locking scheme in SLUB to reflect changes done
by this series.

[ Mike Galbraith <efault@gmx.de>: use local_lock() without irq in PREEMPT_RT
  scope; debugging of RT crashes resulting in put_cpu_partial() locking changes ]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 10:22:01 +02:00
Vlastimil Babka 25c00c506e mm, slub: use migrate_disable() on PREEMPT_RT
We currently use preempt_disable() (directly or via get_cpu_ptr()) to stabilize
the pointer to kmem_cache_cpu. On PREEMPT_RT this would be incompatible with
the list_lock spinlock. We can use migrate_disable() instead, but that
increases overhead on !PREEMPT_RT as it's an unconditional function call.

In order to get the best available mechanism on both PREEMPT_RT and
!PREEMPT_RT, introduce private slub_get_cpu_ptr() and slub_put_cpu_ptr()
wrappers and use them.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 10:21:32 +02:00
Vlastimil Babka e0a043aa41 mm, slub: protect put_cpu_partial() with disabled irqs instead of cmpxchg
Jann Horn reported [1] the following theoretically possible race:

  task A: put_cpu_partial() calls preempt_disable()
  task A: oldpage = this_cpu_read(s->cpu_slab->partial)
  interrupt: kfree() reaches unfreeze_partials() and discards the page
  task B (on another CPU): reallocates page as page cache
  task A: reads page->pages and page->pobjects, which are actually
  halves of the pointer page->lru.prev
  task B (on another CPU): frees page
  interrupt: allocates page as SLUB page and places it on the percpu partial list
  task A: this_cpu_cmpxchg() succeeds

  which would cause page->pages and page->pobjects to end up containing
  halves of pointers that would then influence when put_cpu_partial()
  happens and show up in root-only sysfs files. Maybe that's acceptable,
  I don't know. But there should probably at least be a comment for now
  to point out that we're reading union fields of a page that might be
  in a completely different state.

Additionally, the this_cpu_cmpxchg() approach in put_cpu_partial() is only safe
against s->cpu_slab->partial manipulation in ___slab_alloc() if the latter
disables irqs, otherwise a __slab_free() in an irq handler could call
put_cpu_partial() in the middle of ___slab_alloc() manipulating ->partial
and corrupt it. This becomes an issue on RT after a local_lock is introduced
in later patch. The fix means taking the local_lock also in put_cpu_partial()
on RT.

After debugging this issue, Mike Galbraith suggested [2] that to avoid
different locking schemes on RT and !RT, we can just protect put_cpu_partial()
with disabled irqs (to be converted to local_lock_irqsave() later) everywhere.
This should be acceptable as it's not a fast path, and moving the actual
partial unfreezing outside of the irq disabled section makes it short, and with
the retry loop gone the code can be also simplified. In addition, the race
reported by Jann should no longer be possible.

[1] https://lore.kernel.org/lkml/CAG48ez1mvUuXwg0YPH5ANzhQLpbphqk-ZS+jbRz+H66fvm4FcA@mail.gmail.com/
[2] https://lore.kernel.org/linux-rt-users/e3470ab357b48bccfbd1f5133b982178a7d2befb.camel@gmx.de/

Reported-by: Jann Horn <jannh@google.com>
Suggested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 10:20:10 +02:00
Vlastimil Babka a2b4ae8bfd mm, slub: make slab_lock() disable irqs with PREEMPT_RT
We need to disable irqs around slab_lock() (a bit spinlock) to make it
irq-safe. Most calls to slab_lock() are nested under spin_lock_irqsave() which
doesn't disable irqs on PREEMPT_RT, so add explicit disabling with PREEMPT_RT.
The exception is cmpxchg_double_slab() which already disables irqs, so use a
__slab_[un]lock() variant without irq disable there.

slab_[un]lock() thus needs a flags pointer parameter, which is unused on !RT.
free_debug_processing() now has two flags variables, which looks odd, but only
one is actually used - the one used in spin_lock_irqsave() on !RT and the one
used in slab_lock() on RT.

As a result, __cmpxchg_double_slab() and cmpxchg_double_slab() become
effectively identical on RT, as both will disable irqs, which is necessary on
RT as most callers of this function also rely on irqsaving lock operations.
Thus, assert that irqs are already disabled in __cmpxchg_double_slab() only on
!RT and also change the VM_BUG_ON assertion to the more standard lockdep_assert
one.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 10:17:33 +02:00
Sebastian Andrzej Siewior 94ef0304e2 mm: slub: make object_map_lock a raw_spinlock_t
The variable object_map is protected by object_map_lock. The lock is always
acquired in debug code and within already atomic context

Make object_map_lock a raw_spinlock_t.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 10:16:45 +02:00
Sebastian Andrzej Siewior 5a836bf6b0 mm: slub: move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context
flush_all() flushes a specific SLAB cache on each CPU (where the cache
is present). The deactivate_slab()/__free_slab() invocation happens
within IPI handler and is problematic for PREEMPT_RT.

The flush operation is not a frequent operation or a hot path. The
per-CPU flush operation can be moved to within a workqueue.

Because a workqueue handler, unlike IPI handler, does not disable irqs,
flush_slab() now has to disable them for working with the kmem_cache_cpu
fields. deactivate_slab() is safe to call with irqs enabled.

[vbabka@suse.cz: adapt to new SLUB changes]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 01:12:23 +02:00
Vlastimil Babka 08beb547a1 mm, slab: split out the cpu offline variant of flush_slab()
flush_slab() is called either as part IPI handler on given live cpu, or as a
cleanup on behalf of another cpu that went offline. The first case needs to
protect updating the kmem_cache_cpu fields with disabled irqs. Currently the
whole call happens with irqs disabled by the IPI handler, but the following
patch will change from IPI to workqueue, and flush_slab() will have to disable
irqs (to be replaced with a local lock later) in the critical part.

To prepare for this change, replace the call to flush_slab() for the dead cpu
handling with an opencoded variant that will not disable irqs nor take a local
lock.

Suggested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 01:12:22 +02:00
Vlastimil Babka 0e7ac738f7 mm, slub: don't disable irqs in slub_cpu_dead()
slub_cpu_dead() cleans up for an offlined cpu from another cpu and calls only
functions that are now irq safe, so we don't need to disable irqs anymore.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 01:12:22 +02:00
Vlastimil Babka 7cf9f3ba2f mm, slub: only disable irq with spin_lock in __unfreeze_partials()
__unfreeze_partials() no longer needs to have irqs disabled, except for making
the spin_lock operations irq-safe, so convert the spin_locks operations and
remove the separate irq handling.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2021-09-04 01:12:22 +02:00