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Mon, 20 Jan 2020 13:38:40 +0000 (UTC) Received: from [10.36.118.34] (unknown [10.36.118.34]) by smtp.corp.redhat.com (Postfix) with ESMTP id EC42F60C05; Mon, 20 Jan 2020 13:38:38 +0000 (UTC) Subject: Re: [PATCH -mm v2] mm/page_isolation: fix potential warning from user From: David Hildenbrand To: Qian Cai , akpm@linux-foundation.org Cc: mhocko@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200120131909.813-1-cai@lca.pw> <8c56268d-9b8a-f62e-eca9-7707852a2aaf@redhat.com> Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Mon, 20 Jan 2020 14:38:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <8c56268d-9b8a-f62e-eca9-7707852a2aaf@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 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: On 20.01.20 14:30, David Hildenbrand wrote: > On 20.01.20 14:19, Qian Cai wrote: >> It makes sense to call the WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE) >> from start_isolate_page_range(), but should avoid triggering it from >> userspace, i.e, from is_mem_section_removable() because it could be a >> DoS if warn_on_panic is set. >> >> While at it, simplify the code a bit by removing an unnecessary jump >> label and a local variable, so set_migratetype_isolate() could really >> return a bool. >> >> Suggested-by: Michal Hocko >> Signed-off-by: Qian Cai >> --- >> >> v2: Improve the commit log. >> Warn for all start_isolate_page_range() users not just offlining. >> >> mm/page_alloc.c | 11 ++++------- >> mm/page_isolation.c | 30 +++++++++++++++++------------- >> 2 files changed, 21 insertions(+), 20 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 621716a25639..3c4eb750a199 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -8231,7 +8231,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, >> if (is_migrate_cma(migratetype)) >> return NULL; >> >> - goto unmovable; >> + return page; >> } >> >> for (; iter < pageblock_nr_pages; iter++) { >> @@ -8241,7 +8241,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, >> page = pfn_to_page(pfn + iter); >> >> if (PageReserved(page)) >> - goto unmovable; >> + return page; >> >> /* >> * If the zone is movable and we have ruled out all reserved >> @@ -8261,7 +8261,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, >> unsigned int skip_pages; >> >> if (!hugepage_migration_supported(page_hstate(head))) >> - goto unmovable; >> + return page; >> >> skip_pages = compound_nr(head) - (page - head); >> iter += skip_pages - 1; >> @@ -8303,12 +8303,9 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, >> * is set to both of a memory hole page and a _used_ kernel >> * page at boot. >> */ >> - goto unmovable; >> + return page; >> } >> return NULL; >> -unmovable: >> - WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE); >> - return pfn_to_page(pfn + iter); >> } >> >> #ifdef CONFIG_CONTIG_ALLOC >> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >> index e70586523ca3..31f5516f5d54 100644 >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -15,12 +15,12 @@ >> #define CREATE_TRACE_POINTS >> #include >> >> -static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags) >> +static bool set_migratetype_isolate(struct page *page, int migratetype, >> + int isol_flags) > > Why this change? > >> { >> - struct page *unmovable = NULL; >> + struct page *unmovable = ERR_PTR(-EBUSY); > > Also, why this change? > >> struct zone *zone; >> unsigned long flags; >> - int ret = -EBUSY; >> >> zone = page_zone(page); >> >> @@ -49,21 +49,25 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ >> NULL); >> >> __mod_zone_freepage_state(zone, -nr_pages, mt); >> - ret = 0; >> } >> >> out: >> spin_unlock_irqrestore(&zone->lock, flags); >> - if (!ret) >> + >> + if (!unmovable) { >> drain_all_pages(zone); >> - else if ((isol_flags & REPORT_FAILURE) && unmovable) >> - /* >> - * printk() with zone->lock held will guarantee to trigger a >> - * lockdep splat, so defer it here. >> - */ >> - dump_page(unmovable, "unmovable page"); >> - >> - return ret; >> + } else { >> + WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE); >> + >> + if ((isol_flags & REPORT_FAILURE) && !IS_ERR(unmovable)) >> + /* > > Why this change? (!IS_ERR) > > > Some things here look unrelated - or I am missing something :) > FWIW, I'd prefer this change without any such cleanups (e.g., I don't like returning a bool from this function and the IS_ERR handling, makes the function harder to read than before) -- Thanks, David / dhildenb