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Wed, 23 Oct 2019 16:15:44 +0000 (UTC) Subject: Re: [RFC PATCH 1/2] mm, vmstat: hide /proc/pagetypeinfo from normal users To: Michal Hocko , Andrew Morton , Mel Gorman , Waiman Long Cc: Johannes Weiner , Roman Gushchin , Konstantin Khlebnikov , Jann Horn , Song Liu , Greg Kroah-Hartman , Rafael Aquini , linux-mm@kvack.org, LKML , Michal Hocko , Linux API References: <20191023095607.GE3016@techsingularity.net> <20191023102737.32274-1-mhocko@kernel.org> <20191023102737.32274-2-mhocko@kernel.org> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; prefer-encrypt=mutual; keydata= mQINBFZdmxYBEADsw/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 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABtCBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PokCVAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJcbbyGBQkH8VTqAAoJECJPp+fMgqZkpGoP /1jhVihakxw1d67kFhPgjWrbzaeAYOJu7Oi79D8BL8Vr5dmNPygbpGpJaCHACWp+10KXj9yz fWABs01KMHnZsAIUytVsQv35DMMDzgwVmnoEIRBhisMYOQlH2bBn/dqBjtnhs7zTL4xtqEcF 1hoUFEByMOey7gm79utTk09hQE/Zo2x0Ikk98sSIKBETDCl4mkRVRlxPFl4O/w8dSaE4eczH LrKezaFiZOv6S1MUKVKzHInonrCqCNbXAHIeZa3JcXCYj1wWAjOt9R3NqcWsBGjFbkgoKMGD usiGabetmQjXNlVzyOYdAdrbpVRNVnaL91sB2j8LRD74snKsV0Wzwt90YHxDQ5z3M75YoIdl byTKu3BUuqZxkQ/emEuxZ7aRJ1Zw7cKo/IVqjWaQ1SSBDbZ8FAUPpHJxLdGxPRN8Pfw8blKY 8mvLJKoF6i9T6+EmlyzxqzOFhcc4X5ig5uQoOjTIq6zhLO+nqVZvUDd2Kz9LMOCYb516cwS/ Enpi0TcZ5ZobtLqEaL4rupjcJG418HFQ1qxC95u5FfNki+YTmu6ZLXy+1/9BDsPuZBOKYpUm 3HWSnCS8J5Ny4SSwfYPH/JrtberWTcCP/8BHmoSpS/3oL3RxrZRRVnPHFzQC6L1oKvIuyXYF rkybPXYbmNHN+jTD3X8nRqo+4Qhmu6SHi3VquQENBFsZNQwBCACuowprHNSHhPBKxaBX7qOv KAGCmAVhK0eleElKy0sCkFghTenu1sA9AV4okL84qZ9gzaEoVkgbIbDgRbKY2MGvgKxXm+kY n8tmCejKoeyVcn9Xs0K5aUZiDz4Ll9VPTiXdf8YcjDgeP6/l4kHb4uSW4Aa9ds0xgt0gP1Xb AMwBlK19YvTDZV5u3YVoGkZhspfQqLLtBKSt3FuxTCU7hxCInQd3FHGJT/IIrvm07oDO2Y8J DXWHGJ9cK49bBGmK9B4ajsbe5GxtSKFccu8BciNluF+BqbrIiM0upJq5Xqj4y+Xjrpwqm4/M ScBsV0Po7qdeqv0pEFIXKj7IgO/d4W2bABEBAAGJA3IEGAEKACYWIQSpQNQ0mSwujpkQPVAi T6fnzIKmZAUCWxk1DAIbAgUJA8JnAAFACRAiT6fnzIKmZMB0IAQZAQoAHRYhBKZ2GgCcqNxn k0Sx9r6Fd25170XjBQJbGTUMAAoJEL6Fd25170XjDBUH/2jQ7a8g+FC2qBYxU/aCAVAVY0NE YuABL4LJ5+iWwmqUh0V9+lU88Cv4/G8fWwU+hBykSXhZXNQ5QJxyR7KWGy7LiPi7Cvovu+1c 9Z9HIDNd4u7bxGKMpn19U12ATUBHAlvphzluVvXsJ23ES/F1c59d7IrgOnxqIcXxr9dcaJ2K k9VP3TfrjP3g98OKtSsyH0xMu0MCeyewf1piXyukFRRMKIErfThhmNnLiDbaVy6biCLx408L Mo4cCvEvqGKgRwyckVyo3JuhqreFeIKBOE1iHvf3x4LU8cIHdjhDP9Wf6ws1XNqIvve7oV+w B56YWoalm1rq00yUbs2RoGcXmtX1JQ//aR/paSuLGLIb3ecPB88rvEXPsizrhYUzbe1TTkKc 4a4XwW4wdc6pRPVFMdd5idQOKdeBk7NdCZXNzoieFntyPpAq+DveK01xcBoXQ2UktIFIsXey uSNdLd5m5lf7/3f0BtaY//f9grm363NUb9KBsTSnv6Vx7Co0DWaxgC3MFSUhxzBzkJNty+2d 10jvtwOWzUN+74uXGRYSq5WefQWqqQNnx+IDb4h81NmpIY/X0PqZrapNockj3WHvpbeVFAJ0 9MRzYP3x8e5OuEuJfkNnAbwRGkDy98nXW6fKeemREjr8DWfXLKFWroJzkbAVmeIL0pjXATxr +tj5JC0uvMrrXefUhXTo0SNoTsuO/OsAKOcVsV/RHHTwCDR2e3W8mOlA3QbYXsscgjghbuLh J3oTRrOQa8tUXWqcd5A0+QPo5aaMHIK0UAthZsry5EmCY3BrbXUJlt+23E93hXQvfcsmfi0N rNh81eknLLWRYvMOsrbIqEHdZBT4FHHiGjnck6EYx/8F5BAZSodRVEAgXyC8IQJ+UVa02QM5 D2VL8zRXZ6+wARKjgSrW+duohn535rG/ypd0ctLoXS6dDrFokwTQ2xrJiLbHp9G+noNTHSan ExaRzyLbvmblh3AAznb68cWmM3WVkceWACUalsoTLKF1sGrrIBj5updkKkzbKOq5gcC5AQ0E Wxk1NQEIAJ9B+lKxYlnKL5IehF1XJfknqsjuiRzj5vnvVrtFcPlSFL12VVFVUC2tT0A1Iuo9 NAoZXEeuoPf1dLDyHErrWnDyn3SmDgb83eK5YS/K363RLEMOQKWcawPJGGVTIRZgUSgGusKL NuZqE5TCqQls0x/OPljufs4gk7E1GQEgE6M90Xbp0w/r0HB49BqjUzwByut7H2wAdiNAbJWZ F5GNUS2/2IbgOhOychHdqYpWTqyLgRpf+atqkmpIJwFRVhQUfwztuybgJLGJ6vmh/LyNMRr8 J++SqkpOFMwJA81kpjuGR7moSrUIGTbDGFfjxmskQV/W/c25Xc6KaCwXah3OJ40AEQEAAYkC PAQYAQoAJhYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJbGTU1AhsMBQkDwmcAAAoJECJPp+fM gqZkPN4P/Ra4NbETHRj5/fM1fjtngt4dKeX/6McUPDIRuc58B6FuCQxtk7sX3ELs+1+w3eSV rHI5cOFRSdgw/iKwwBix8D4Qq0cnympZ622KJL2wpTPRLlNaFLoe5PkoORAjVxLGplvQIlhg miljQ3R63ty3+MZfkSVsYITlVkYlHaSwP2t8g7yTVa+q8ZAx0NT9uGWc/1Sg8j/uoPGrctml hFNGBTYyPq6mGW9jqaQ8en3ZmmJyw3CHwxZ5FZQ5qc55xgshKiy8jEtxh+dgB9d8zE/S/UGI E99N/q+kEKSgSMQMJ/CYPHQJVTi4YHh1yq/qTkHRX+ortrF5VEeDJDv+SljNStIxUdroPD29 2ijoaMFTAU+uBtE14UP5F+LWdmRdEGS1Ah1NwooL27uAFllTDQxDhg/+LJ/TqB8ZuidOIy1B xVKRSg3I2m+DUTVqBy7Lixo73hnW69kSjtqCeamY/NSu6LNP+b0wAOKhwz9hBEwEHLp05+mj 5ZFJyfGsOiNUcMoO/17FO4EBxSDP3FDLllpuzlFD7SXkfJaMWYmXIlO0jLzdfwfcnDzBbPwO hBM8hvtsyq8lq8vJOxv6XD6xcTtj5Az8t2JjdUX6SF9hxJpwhBU0wrCoGDkWp4Bbv6jnF7zP Nzftr4l8RuJoywDIiJpdaNpSlXKpj/K6KrnyAI/joYc7 Message-ID: Date: Wed, 23 Oct 2019 18:15:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <20191023102737.32274-2-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: + linux-api On 10/23/19 12:27 PM, Michal Hocko wrote: > From: Michal Hocko > > /proc/pagetypeinfo is a debugging tool to examine internal page > allocator state wrt to fragmentation. It is not very useful for > any other use so normal users really do not need to read this file. > > Waiman Long has noticed that reading this file can have negative side > effects because zone->lock is necessary for gathering data and that > a) interferes with the page allocator and its users and b) can lead to > hard lockups on large machines which have very long free_list. > > Reduce both issues by simply not exporting the file to regular users. > > Reported-by: Waiman Long > Cc: stable > Signed-off-by: Michal Hocko > --- > mm/vmstat.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmstat.c b/mm/vmstat.c > index 6afc892a148a..4e885ecd44d1 100644 > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -1972,7 +1972,7 @@ void __init init_mm_internals(void) > #endif > #ifdef CONFIG_PROC_FS > proc_create_seq("buddyinfo", 0444, NULL, &fragmentation_op); > - proc_create_seq("pagetypeinfo", 0444, NULL, &pagetypeinfo_op); > + proc_create_seq("pagetypeinfo", 0400, NULL, &pagetypeinfo_op); > proc_create_seq("vmstat", 0444, NULL, &vmstat_op); > proc_create_seq("zoneinfo", 0444, NULL, &zoneinfo_op); > #endif >