From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3515D347C7 for ; Fri, 8 Aug 2025 13:38:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754660292; cv=none; b=hqnew67TqcgihsI9B2NddMaTT4s/LPc8ti1bMEh81bwB/2KZDqQroTdc9QnZPaeyo/XzrMMCx2/GQ12E2UY1lu0fdbKEHbgPtV64xZeOCQDmMYp6z3fGJs+k7xgkLpojdO3QTunyxy7N1gQ8AeUHMx0J28ek2M3HFNczveXH/wA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754660292; c=relaxed/simple; bh=kSLHC9axIk6gpHeD5+Ar5IeslvLP3AcQ4iQ4pjdyeXE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=imTwHDNfe75QfQ/Kn7RCzBjeg5dxvl8dpGH732llicmJHdGWHqHhas8i0IhNkxLIzHK/dEYxkFLnyxDcQDPFS4ZSZTn2cFqAP+QB1yvI0mlz7c1YVajPm5kXSR5n+MF051a1qyNcbBFA0GQZ7H0kdOM0bOcFlYAaSlKBazwdFWY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=jLF+N0aw; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=CFsAjIL4; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=Wf9oqIf4; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=HmOZJJv8; arc=none smtp.client-ip=195.135.223.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="jLF+N0aw"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="CFsAjIL4"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="Wf9oqIf4"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="HmOZJJv8" Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 77BD55BDEE; Fri, 8 Aug 2025 13:38:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1754660288; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Cf1tw1RRJzo2VbFxxZUkyEDgUrYDcKWwz8TA4er43A0=; b=jLF+N0awpVsAV6SbqvZF2hrBhyyWoPSEb8cKKnjxIYZJk584zY5HG2mp3YeB8kE4mbWzY/ cEBbHcWDPR+gNrNSvjx9nGANVDOmTZOdvaD7s9NMlGihOE6AMyThD2isID53gA/Rom2hkt HBtTZF1vt4IAojtVwGQTtpM1J4ZuyMQ= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1754660288; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Cf1tw1RRJzo2VbFxxZUkyEDgUrYDcKWwz8TA4er43A0=; b=CFsAjIL43c2pVTHHzdlPa1ra72EBApokvtjBoAqwX4jQ4KpquAmf1ZwvBfQ3qbBFluoi9R 0Y4kjGBPqJwtvzCw== Authentication-Results: smtp-out2.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1754660287; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Cf1tw1RRJzo2VbFxxZUkyEDgUrYDcKWwz8TA4er43A0=; b=Wf9oqIf4rX0b4fPxCR/Y5Cu4kZh3o8CFQlRY9F+8kFJZZkPS4M8oMnEoWIKy73mZgcuhEk PGYieFJMl3lkrwIBiLDhi24AKA4gAgL1bAjPCxBas36yJZnIJwQA38J3UiBnRvW0YSx8Ir 9zRJsLSpCFFnPXTfNtwQ+vhFizMOXEg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1754660287; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Cf1tw1RRJzo2VbFxxZUkyEDgUrYDcKWwz8TA4er43A0=; b=HmOZJJv8MYRl5yvrO9mE/tL0w14AfPfT9HGHuKr9pR4kp4bgkfTgNvlUqLjhBFvh8Rbq4x WD5OJWSFdFzKS2Dg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 54C151392A; Fri, 8 Aug 2025 13:38:07 +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 e9BZFL/9lWgMJgAAD6G6ig (envelope-from ); Fri, 08 Aug 2025 13:38:07 +0000 Message-ID: Date: Fri, 8 Aug 2025 15:38:07 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.17 1/3] mm/mremap: allow multi-VMA move when filesystem uses thp_get_unmapped_area To: Lorenzo Stoakes , Andrew Morton Cc: "Liam R . Howlett" , Jann Horn , Pedro Falcato , David Hildenbrand , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <4f2542340c29c84d3d470b0c605e916b192f6c81.1754218667.git.lorenzo.stoakes@oracle.com> Content-Language: en-US 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+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <4f2542340c29c84d3d470b0c605e916b192f6c81.1754218667.git.lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.997]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[11]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:mid,suse.cz:email] X-Spam-Flag: NO X-Spam-Level: X-Spam-Score: -4.30 On 8/3/25 13:11, Lorenzo Stoakes wrote: > We currently restrict multi-VMA move to avoid filesystems or drivers which > provide a custom f_op->get_unmapped_area handler unless it is known to > correctly handle MREMAP_FIXED. > > We do this so we do not get unexpected result when moving from one area to > another (for instance, if the handler would align things resulting in the > moved VMAs having different gaps than the original mapping). > > More and more filesystems are moving to using large folios, and typically > do so (in part) by setting f_op->get_unmapped_area to > thp_get_unmapped_area. > > When mremap() invokes the file system's get_unmapped MREMAP_FIXED, it does > so via get_unmapped_area(), called in vrm_set_new_addr(). In order to do > so, it converts the MREMAP_FIXED flag to a MAP_FIXED flag and passes this > to the unmapped area handler. > > The __get_unmapped_area() function (called by get_unmapped_area()) in turn > invokes the filesystem or driver's f_op->get_unmapped_area() handler. > > Therefore this is a point at which thp_get_unmapped_area() may be called > (also, this is the case for anonymous mappings where the size is huge page > aligned). > > thp_get_unmapped_area() calls thp_get_unmapped_area_vmflags() and > __thp_get_unmapped_area() in turn (falling back to > mm_get_unmapped_area_vm_flags() which is known to handle MAP_FIXED > correctly). > > The __thp_get_unmapped_area() function in turn does nothing to change the > address hint, nor the MAP_FIXED flag, only adjusting alignment > parameters. It hten calls mm_get_unmapped_area_vmflags(), and in turn > arch-specific unmapped area functions, all of which honour MAP_FIXED > correctly. > > Therefore, we can safely add thp_get_unmapped_area to the known-good > handlers. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka