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Fri, 25 Oct 2024 21:56:52 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id RDLHNCQUHGetWwAAD6G6ig (envelope-from ); Fri, 25 Oct 2024 21:56:52 +0000 Message-ID: <7c7185ed-f997-484a-b1d1-91ae6c761266@suse.cz> Date: Fri, 25 Oct 2024 23:56:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/5] mm: madvise: implement lightweight guard page mechanism Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , "Paul E . McKenney" , Jann Horn , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Richard Henderson , Matt Turner , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Chris Zankel , Max Filippov , Arnd Bergmann , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org, Shuah Khan , Christian Brauner , linux-kselftest@vger.kernel.org, Sidhartha Kumar , Jeff Xu , Christoph Hellwig , linux-api@vger.kernel.org, John Hubbard References: <415da1e6c5828d96db3af480d243a7f68ccabf6d.1729699916.git.lorenzo.stoakes@oracle.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: B3E9014000F X-Rspamd-Server: rspam01 X-Stat-Signature: 1xptfqj7ays1xokq3hx9jzgqe3auppz6 X-HE-Tag: 1729893399-78221 X-HE-Meta: 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 SmTUEf/+ 4kd/+qMhe1nKVYBQOJ6hPTgTqjbW0CUsFjDU1KbU+1RUaWYnyqID22esTQaYHNkg9HlA4Oakf9MqzpZX0Dogh88Txnj1bWNjjHSd8Em8sixLyzVQEbXSE6qV29DDWLA02ud9gWY3HFsxo1Hb0J3iG3ccbzQoev5XN48lS3UG39ug+sdyBExD24FhBZtseEAnuS3x7zgc8GPO/NDNXO+UkZadnzwUZBmgax+kWAnf54EBDogWIeIzE7Dv7Wd0BuMagA1lHG4+vF223jso6mKFvutXrJ+uMzpOl2WdPTEOHkfMMN7Uh3BzfGekMyg== 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: On 10/25/24 19:12, Lorenzo Stoakes wrote: > On Wed, Oct 23, 2024 at 05:24:40PM +0100, Lorenzo Stoakes wrote: >> Implement a new lightweight guard page feature, that is regions of userland >> virtual memory that, when accessed, cause a fatal signal to arise. > > > > Hi Andrew - Could you apply the below fix-patch? I realise we must handle > fatal signals and conditional rescheduling in the vector_madvise() special > case. > > Thanks! > > ----8<---- > From 546d7e1831c71599fc733d589e0d75f52e84826d Mon Sep 17 00:00:00 2001 > From: Lorenzo Stoakes > Date: Fri, 25 Oct 2024 18:05:48 +0100 > Subject: [PATCH] mm: yield on fatal signal/cond_sched() in vector_madvise() > > While we have to treat -ERESTARTNOINTR specially here as we are looping > through a vector of operations and can't simply restart the entire > operation, we mustn't hold up fatal signals or RT kernels. For plain madvise() syscall returning -ERESTARTNOINTR does the right thing and checks fatal_signal_pending() before returning, right? Uh actually can we be just returning -ERESTARTNOINTR or do we need to use restart_syscall()? > --- > mm/madvise.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 48eba25e25fe..127aa5d86656 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -1713,8 +1713,14 @@ static ssize_t vector_madvise(struct mm_struct *mm, struct iov_iter *iter, > * we have already rescinded locks, it should be no problem to > * simply try again. > */ > - if (ret == -ERESTARTNOINTR) > + if (ret == -ERESTARTNOINTR) { > + if (fatal_signal_pending(current)) { > + ret = -EINTR; > + break; > + } > + cond_resched(); Should be unnecessary as we're calling an operation that takes a rwsem so there are reschedule points already. And with lazy preempt hopefully cond_resched()s will become history, so let's not add more only to delete later. > continue; > + } > if (ret < 0) > break; > iov_iter_advance(iter, iter_iov_len(iter)); > -- > 2.47.0