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mm, slub: call deactivate_slab() without disabling irqs 

The function is now safe to be called with irqs enabled, so move the calls
outside of irq disabled sections.

When called from ___slab_alloc() -> flush_slab() we have irqs disabled, so to
reenable them before deactivate_slab() we need to open-code flush_slab() in
___slab_alloc() and reenable irqs after modifying the kmem_cache_cpu fields.
But that means a IRQ handler meanwhile might have assigned a new page to
kmem_cache_cpu.page so we have to retry the whole check.

The remaining callers of flush_slab() are the IPI handler which has disabled
irqs anyway, and slub_cpu_dead() which will be dealt with in the following
patch.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Vlastimil Babka 2021-05-12 14:04:43 +02:00
parent 3406e91bce
commit cfdf836e1f
1 changed files with 19 additions and 5 deletions
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24
mm/slub.c
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@ -2779,8 +2779,8 @@ deactivate_slab:
freelist = c->freelist;
c->page = NULL;
c->freelist = NULL;
deactivate_slab(s, page, freelist);
local_irq_restore(flags);
deactivate_slab(s, page, freelist);
new_slab:
@ -2848,18 +2848,32 @@ check_new_page:
*/
goto return_single;
retry_load_page:
local_irq_save(flags);
if (unlikely(c->page))
flush_slab(s, c);
if (unlikely(c->page)) {
void *flush_freelist = c->freelist;
struct page *flush_page = c->page;
c->page = NULL;
c->freelist = NULL;
c->tid = next_tid(c->tid);
local_irq_restore(flags);
deactivate_slab(s, flush_page, flush_freelist);
stat(s, CPUSLAB_FLUSH);
goto retry_load_page;
}
c->page = page;
goto load_freelist;
return_single:
local_irq_save(flags);
deactivate_slab(s, page, get_freepointer(s, freelist));
local_irq_restore(flags);
return freelist;
}