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Tsirkin" , Jason Wang , Xuan Zhuo , =?utf-8?q?Eugenio_P=C3=A9rez?= , Maxime Coquelin Subject: [PATCH RFC 1/5] vpda: try to fix the potential crash due to misusing __GFP_NOFAIL Date: Wed, 24 Jul 2024 20:55:40 +1200 Message-Id: <20240724085544.299090-2-21cnbao@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240724085544.299090-1-21cnbao@gmail.com> References: <20240724085544.299090-1-21cnbao@gmail.com> MIME-Version: 1.0 X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: E2A9F180013 X-Stat-Signature: kj6gfmdnmeyju6nhzsfzkktznpo1jyiu X-HE-Tag: 1721811371-210393 X-HE-Meta: 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 85JG0yJA 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Barry Song mm doesn't support non-blockable __GFP_NOFAIL allocation. Because __GFP_NOFAIL without direct reclamation may just result in a busy loop within non-sleepable contexts. static inline struct page * __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, struct alloc_context *ac) { ... /* * Make sure that __GFP_NOFAIL request doesn't leak out and make sure * we always retry */ if (gfp_mask & __GFP_NOFAIL) { /* * All existing users of the __GFP_NOFAIL are blockable, so warn * of any new users that actually require GFP_NOWAIT */ if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask)) goto fail; ... } ... fail: warn_alloc(gfp_mask, ac->nodemask, "page allocation failure: order:%u", order); got_pg: return page; } Let's move the memory allocation out of the atomic context and use the normal sleepable context to get pages. [RFC]: This has only been compile-tested; I'd prefer if the VDPA maintainers handles it. Cc: "Michael S. Tsirkin" Cc: Jason Wang Cc: Xuan Zhuo Cc: "Eugenio Pérez" Cc: Maxime Coquelin Signed-off-by: Barry Song Signed-off-by: Barry Song --- drivers/vdpa/vdpa_user/iova_domain.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/drivers/vdpa/vdpa_user/iova_domain.c b/drivers/vdpa/vdpa_user/iova_domain.c index 791d38d6284c..eff700e5f7a2 100644 --- a/drivers/vdpa/vdpa_user/iova_domain.c +++ b/drivers/vdpa/vdpa_user/iova_domain.c @@ -287,28 +287,44 @@ void vduse_domain_remove_user_bounce_pages(struct vduse_iova_domain *domain) { struct vduse_bounce_map *map; unsigned long i, count; + struct page **pages = NULL; write_lock(&domain->bounce_lock); if (!domain->user_bounce_pages) goto out; - count = domain->bounce_size >> PAGE_SHIFT; + write_unlock(&domain->bounce_lock); + + pages = kmalloc_array(count, sizeof(*pages), GFP_KERNEL | __GFP_NOFAIL); + for (i = 0; i < count; i++) + pages[i] = alloc_page(GFP_KERNEL | __GFP_NOFAIL); + + write_lock(&domain->bounce_lock); + if (!domain->user_bounce_pages) { + for (i = 0; i < count; i++) + put_page(pages[i]); + kfree(pages); + goto out; + } + for (i = 0; i < count; i++) { - struct page *page = NULL; + struct page *page = pages[i]; map = &domain->bounce_maps[i]; - if (WARN_ON(!map->bounce_page)) + if (WARN_ON(!map->bounce_page)) { + put_page(page); continue; + } /* Copy user page to kernel page if it's in use */ if (map->orig_phys != INVALID_PHYS_ADDR) { - page = alloc_page(GFP_ATOMIC | __GFP_NOFAIL); memcpy_from_page(page_address(page), map->bounce_page, 0, PAGE_SIZE); } put_page(map->bounce_page); map->bounce_page = page; } + kfree(pages); domain->user_bounce_pages = false; out: write_unlock(&domain->bounce_lock);