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    Subject[PATCH v3 15/35] mm, slub: restore irqs around calling new_slab()
    Date
    allocate_slab() currently re-enables irqs before calling to the page allocator.
    It depends on gfpflags_allow_blocking() to determine if it's safe to do so.
    Now we can instead simply restore irq before calling it through new_slab().
    The other caller early_kmem_cache_node_alloc() is unaffected by this.

    Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
    ---
    mm/slub.c | 8 ++------
    1 file changed, 2 insertions(+), 6 deletions(-)

    diff --git a/mm/slub.c b/mm/slub.c
    index 187424ebf1d8..43f38fd47062 100644
    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -1792,9 +1792,6 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)

    flags &= gfp_allowed_mask;

    - if (gfpflags_allow_blocking(flags))
    - local_irq_enable();
    -
    flags |= s->allocflags;

    /*
    @@ -1853,8 +1850,6 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
    page->frozen = 1;

    out:
    - if (gfpflags_allow_blocking(flags))
    - local_irq_disable();
    if (!page)
    return NULL;

    @@ -2782,16 +2777,17 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
    goto check_new_page;
    }

    + local_irq_restore(flags);
    put_cpu_ptr(s->cpu_slab);
    page = new_slab(s, gfpflags, node);
    c = get_cpu_ptr(s->cpu_slab);

    if (unlikely(!page)) {
    - local_irq_restore(flags);
    slab_out_of_memory(s, gfpflags, node);
    return NULL;
    }

    + local_irq_save(flags);
    if (c->page)
    flush_slab(s, c);

    --
    2.32.0
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