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Tue, 28 Jan 2025 15:05:57 +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 qyj3IlXymGdYXgAAD6G6ig (envelope-from ); Tue, 28 Jan 2025 15:05:57 +0000 Message-ID: Date: Tue, 28 Jan 2025 16:05:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] mm: further refactor commit_merge() Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: "Liam R . Howlett" , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <0bbb2efbdc2ac2af2f6d73679cbb0811544d0647.1737929364.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: <0bbb2efbdc2ac2af2f6d73679cbb0811544d0647.1737929364.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: A79B1160037 X-Stat-Signature: f8w1mm3a8hycq9ecuyxq9pepaqpt6h4t X-Rspam-User: X-HE-Tag: 1738076759-314979 X-HE-Meta: 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 3JaxHZII WbcVzxiFnJBcGlMkjc0L37dAO+oZ+k4A+2SUwbEmmNg5F7EFMTaut4CM9iS2gKipMbYQqkhqMqNi4Q17E9fRt/iO5brraeuZb1yUFAZ8mlL/GD82zBaUlHYpngjb/vUKQktl+fdNpTU0zupOYcvBC+MlvtZxEOR23BHt8EUqAWZ94HwSvsiIaUV5jEbSPgdrN16JKeFNAy06jTpA68Om625ZmgjrBWyNq/Ms4OSql8TsyqONogNahT97S+neU9OBkrrrOfiYd8QQLPxs/QVQthwvXOAwftgjkzzXJHVE41MRHdgPjlsl5yQYPWHkovjEkbnITiABCj6met+zEQP89adCS/FIXvjTSC7zU X-Bogosity: Ham, tests=bogofilter, spamicity=0.000012, 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 1/27/25 16:50, Lorenzo Stoakes wrote: > The current VMA merge mechanism contains a number of confusing mechanisms > around removal of VMAs on merge and the shrinking of the VMA adjacent to > vma->target in the case of merges which result in a partial merge with that > adjacent VMA. > > Since we now have a STABLE set of VMAs - prev, middle, next - we are now > able to have the caller of commit_merge() explicitly tell us which VMAs > need deleting, using newly introduced internal VMA merge flags. > > Doing so allows us to embed this state within the VMG and remove the > confusing remove, remove2 parameters from commit_merge(). > > We additionally are able to eliminate the highly confusing and misleading > 'expanded' parameter - a parameter that in reality refers to whether or not > the return VMA is the target one or the one immediately adjacent. > > We can infer which is the case from whether or not the adj_start parameter > is negative. This also allows us to simplify further logic around iterator > configuration and VMA iterator stores. > > Doing so means we can also eliminate the adjust parameter, as we are able > to infer which VMA ought to be adjusted from adj_start - a positive value > implies we adjust the start of 'middle', a negative one implies we adjust > the start of 'next'. > > We are then able to have commit_merge() explicitly return the target VMA, > or NULL on inability to pre-allocate memory. Errors were previously > filtered so behaviour does not change. > > This patch has no change in functional behaviour. > > Signed-off-by: Lorenzo Stoakes Some of the parts would be quite a hack for a final state of things, but I understand it's a intermediate step for review purposes. Reviewed-by: Vlastimil Babka