diff options
author | 2020-11-15 12:10:29 -0800 | |
---|---|---|
committer | 2020-11-18 15:21:56 -0800 | |
commit | d8c19014bba8f565d8a2f1f46b4e38d1d97bf1a7 (patch) | |
tree | 178b41464b312cbea27acd19bf381880fb90755e /mm/page_alloc.c | |
parent | net: dsa: mv88e6xxx: Wait for EEPROM done after HW reset (diff) | |
download | linux-d8c19014bba8f565d8a2f1f46b4e38d1d97bf1a7.tar.gz linux-d8c19014bba8f565d8a2f1f46b4e38d1d97bf1a7.tar.bz2 linux-d8c19014bba8f565d8a2f1f46b4e38d1d97bf1a7.zip |
page_frag: Recover from memory pressure
The ethernet driver may allocate skb (and skb->data) via napi_alloc_skb().
This ends up to page_frag_alloc() to allocate skb->data from
page_frag_cache->va.
During the memory pressure, page_frag_cache->va may be allocated as
pfmemalloc page. As a result, the skb->pfmemalloc is always true as
skb->data is from page_frag_cache->va. The skb will be dropped if the
sock (receiver) does not have SOCK_MEMALLOC. This is expected behaviour
under memory pressure.
However, once kernel is not under memory pressure any longer (suppose large
amount of memory pages are just reclaimed), the page_frag_alloc() may still
re-use the prior pfmemalloc page_frag_cache->va to allocate skb->data. As a
result, the skb->pfmemalloc is always true unless page_frag_cache->va is
re-allocated, even if the kernel is not under memory pressure any longer.
Here is how kernel runs into issue.
1. The kernel is under memory pressure and allocation of
PAGE_FRAG_CACHE_MAX_ORDER in __page_frag_cache_refill() will fail. Instead,
the pfmemalloc page is allocated for page_frag_cache->va.
2: All skb->data from page_frag_cache->va (pfmemalloc) will have
skb->pfmemalloc=true. The skb will always be dropped by sock without
SOCK_MEMALLOC. This is an expected behaviour.
3. Suppose a large amount of pages are reclaimed and kernel is not under
memory pressure any longer. We expect skb->pfmemalloc drop will not happen.
4. Unfortunately, page_frag_alloc() does not proactively re-allocate
page_frag_alloc->va and will always re-use the prior pfmemalloc page. The
skb->pfmemalloc is always true even kernel is not under memory pressure any
longer.
Fix this by freeing and re-allocating the page instead of recycling it.
References: https://lore.kernel.org/lkml/20201103193239.1807-1-dongli.zhang@oracle.com/
References: https://lore.kernel.org/linux-mm/20201105042140.5253-1-willy@infradead.org/
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Bert Barbe <bert.barbe@oracle.com>
Cc: Rama Nichanamatlu <rama.nichanamatlu@oracle.com>
Cc: Venkat Venkatsubra <venkat.x.venkatsubra@oracle.com>
Cc: Manjunath Patil <manjunath.b.patil@oracle.com>
Cc: Joe Jin <joe.jin@oracle.com>
Cc: SRINIVAS <srinivas.eeda@oracle.com>
Fixes: 79930f5892e1 ("net: do not deplete pfmemalloc reserve")
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20201115201029.11903-1-dongli.zhang@oracle.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r-- | mm/page_alloc.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 23f5066bd4a5..eaa227a479e4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5103,6 +5103,11 @@ refill: if (!page_ref_sub_and_test(page, nc->pagecnt_bias)) goto refill; + if (unlikely(nc->pfmemalloc)) { + free_the_page(page, compound_order(page)); + goto refill; + } + #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE) /* if size can vary use size else just use PAGE_SIZE */ size = nc->size; |