Commit ed4cdfbe authored by Vlastimil Babka's avatar Vlastimil Babka
Browse files

Merge branch 'slab/for-6.4/slob-removal' into slab/for-next 

A series by myself to remove CONFIG_SLOB:

The SLOB allocator was deprecated in 6.2 and there have been no
complaints so far so let's proceed with the removal.

Besides the code cleanup, the main immediate benefit will be allowing
kfree() family of function to work on kmem_cache_alloc() objects, which
was incompatible with SLOB. This includes kfree_rcu() which had no
kmem_cache_free_rcu() counterpart yet and now it shouldn't be necessary
anymore.

Otherwise it's all straightforward removal. After this series, 'git grep
slob' or 'git grep SLOB' will have 3 remaining relevant hits in non-mm
code:

- tomoyo - patch submitted and carried there, doesn't need to wait for
  this series
- skbuff - patch to cleanup now-unnecessary #ifdefs will be posted to
  netdev after this is merged, as requested to avoid conflicts
- ftrace ring_buffer - patch to remove obsolete comment is carried there

The rest of 'git grep SLOB' hits are false positives, or intentional
(CREDITS, and mm/Kconfig SLUB_TINY description to help those that will
happen to migrate later).
parents 8f0293bf ae65a521

Documentation/admin-guide/mm/pagemap.rst

+3 −3
Original line number Diff line number Diff line
@@ -91,9 +91,9 @@ Short descriptions to the page flags 
   The page is being locked for exclusive access, e.g. by undergoing read/write

   IO.

7 - SLAB

   The page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator.

   When compound page is used, SLUB/SLQB will only set this flag on the head

   page; SLOB will not flag it at all.

   The page is managed by the SLAB/SLUB kernel memory allocator.

   When compound page is used, either will only set this flag on the head

   page.

10 - BUDDY

    A free memory block managed by the buddy system allocator.

    The buddy system organizes free memory in blocks of various orders.

Documentation/core-api/memory-allocation.rst

+13 −4
Original line number Diff line number Diff line
@@ -170,7 +170,16 @@ should be used if a part of the cache might be copied to the userspace. 
After the cache is created kmem_cache_alloc() and its convenience

wrappers can allocate memory from that cache.



When the allocated memory is no longer needed it must be freed. You can

use kvfree() for the memory allocated with `kmalloc`, `vmalloc` and

`kvmalloc`. The slab caches should be freed with kmem_cache_free(). And

don't forget to destroy the cache with kmem_cache_destroy().
 
When the allocated memory is no longer needed it must be freed.



Objects allocated by `kmalloc` can be freed by `kfree` or `kvfree`. Objects

allocated by `kmem_cache_alloc` can be freed with `kmem_cache_free`, `kfree`

or `kvfree`, where the latter two might be more convenient thanks to not

needing the kmem_cache pointer.



The same rules apply to _bulk and _rcu flavors of freeing functions.



Memory allocated by `vmalloc` can be freed with `vfree` or `kvfree`.

Memory allocated by `kvmalloc` can be freed with `kvfree`.

Caches created by `kmem_cache_create` should be freed with

`kmem_cache_destroy` only after freeing all the allocated objects first.

fs/proc/page.c

+4 −5
Original line number Diff line number Diff line
@@ -125,7 +125,7 @@ u64 stable_page_flags(struct page *page) 
	/*

	 * pseudo flags for the well known (anonymous) memory mapped pages

	 *

	 * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the

	 * Note that page->_mapcount is overloaded in SLAB, so the

	 * simple test in page_mapped() is not enough.

	 */

	if (!PageSlab(page) && page_mapped(page))
@@ -165,9 +165,8 @@ u64 stable_page_flags(struct page *page) 




	/*

	 * Caveats on high order pages: page->_refcount will only be set

	 * -1 on the head page; SLUB/SLQB do the same for PG_slab;

	 * SLOB won't set PG_slab at all on compound pages.

	 * Caveats on high order pages: PG_buddy and PG_slab will only be set

	 * on the head page.

	 */

	if (PageBuddy(page))

		u |= 1 << KPF_BUDDY;
@@ -185,7 +184,7 @@ u64 stable_page_flags(struct page *page) 
	u |= kpf_copy_bit(k, KPF_LOCKED,	PG_locked);



	u |= kpf_copy_bit(k, KPF_SLAB,		PG_slab);

	if (PageTail(page) && PageSlab(compound_head(page)))

	if (PageTail(page) && PageSlab(page))

		u |= 1 << KPF_SLAB;



	u |= kpf_copy_bit(k, KPF_ERROR,		PG_error);

include/linux/page-flags.h

+0 −4
Original line number Diff line number Diff line
@@ -174,9 +174,6 @@ enum pageflags { 
	/* Remapped by swiotlb-xen. */

	PG_xen_remapped = PG_owner_priv_1,



	/* SLOB */

	PG_slob_free = PG_private,



#ifdef CONFIG_MEMORY_FAILURE

	/*

	 * Compound pages. Stored in first tail page's flags.
@@ -483,7 +480,6 @@ PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD) 
PAGEFLAG(Workingset, workingset, PF_HEAD)

	TESTCLEARFLAG(Workingset, workingset, PF_HEAD)

__PAGEFLAG(Slab, slab, PF_NO_TAIL)

__PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)

PAGEFLAG(Checked, checked, PF_NO_COMPOUND)	   /* Used by some filesystems */



/* Xen */

include/linux/rcupdate.h

+4 −2
Original line number Diff line number Diff line
@@ -976,8 +976,10 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) 
 * either fall back to use of call_rcu() or rearrange the structure to

 * position the rcu_head structure into the first 4096 bytes.

 *

 * Note that the allowable offset might decrease in the future, for example,

 * to allow something like kmem_cache_free_rcu().

 * The object to be freed can be allocated either by kmalloc() or

 * kmem_cache_alloc().

 *

 * Note that the allowable offset might decrease in the future.

 *

 * The BUILD_BUG_ON check must not involve any function calls, hence the

 * checks are done in macros here.