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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22978662508sm22702955ad.139.2025.04.03.21.15.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Apr 2025 21:15:37 -0700 (PDT) Message-ID: Date: Fri, 4 Apr 2025 14:45:32 +1030 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Large folios and filemap_get_folios_contig() To: "Vishal Moola (Oracle)" Cc: Matthew Wilcox , Qu Wenruo , Linux Memory Management List , "linux-fsdevel@vger.kernel.org" , linux-btrfs , vivek.kasireddy@intel.com, Andrew Morton References: <59539c02-d353-4811-bcbe-080b408f445e@suse.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: rpjnqmp9bqsr8qi3b4hqpnbosasaqtb7 X-Rspam-User: X-Rspamd-Queue-Id: E1924C000A X-Rspamd-Server: rspam08 X-HE-Tag: 1743740139-470962 X-HE-Meta: U2FsdGVkX1+Rqo9NJHePWZnNiCPNmVUDB5KL3k+ZX2ICTiDvRQdxkeROa2q1zEUXV525bqEZeXgQvgJMOh0wvpLcbjMULZ3EvhE4F7vAt+qn2naCw+/EZLAxK/LMIkJ7TT4t7KUiPFXTx6909rDc6z8W56klL2m/wp3Nnt91wvEE7vaAdnW0estOWwUuGuYHDIVhTU34OsWz07/Uj+Nj1eqypOvwhEilcSmgXEFMCIXNmChwPQ0nzf6WYQU+2hfmqUWKGOGlBdO2oG9RYU+jTEcZ2xI2J41gr705XSqxa2a/19aKa6sbA3u8GYNDi11U0Qd6bKdmXkyKDzbIFYc+Fi73RoAyZLuunxu9L67WHkHkpz0os/kWED+3JMPOMLMhnc2qKaTBJNJpghJ8WDagJckHzyY94YMK+Ldwo1eH13bhRSRDMrYJvIPYIYk2XrW+hVZWRiknXMk8nqVsPgmdKzXUjYfGynqoQPNbyxqok80W8kbzuGXCIrsf9eQgIakN5TleBaRtJ+i8SUnFhJubJIE8BAU8qlNfeKSmRykGRSEM2cK4pGazcRKxZZUZ5mbdDXH0xMNtqgcvLcyHpPjUyL94sFMcOE7apJiaSH6nSUqGiyJ3KXuGUgF8DsqwhH2NF/1XxMesp134f4nmz15JzSv4AVdT0dZge6LUp6anwJJnPXkUuHEiksx5OASx+jNCQdfKtMeSIqoFuUJnKradZrheJlsF3RPudDSIZl6Daym1t/ydQAkXuJbOFv5FbWO2LyEu3pXTd+MyRSBGS3wQeZkDtTVQffzheI34QtZdcO9VfdF6w4rCwqYN8UseXiTk48n6qiii1Y0Ew4RBznm8Bxei0A8W0aoEftDWZDdlIqcpdFO97MBuerJnmTSipOKSsUXUdhDebWUVEOnyyT9tHE1m1Pjx5wuAxC6tQS2bpqC/qSblvmD8e59iwTiY81DVTO7JNJghK9iXeC/Hrh4 Q8jTZS57 sDOWIb4UhoNM1mp3InyJJTkEbEnFTUg0p2KsEhS+HDYp9a6TlPeoKXvmtg5q3d9OHIxKQ9rZ8qKJ6753fQj5AbRRauhuH3vAVsmjMFRMeaYQ3BpO29fv2lBqw5tbqMe+17V6oElAy5rng6q3gizh9WJVef48fNL5fDlyV99r1nU7WFDkWDuyAcN+P8PDNFHgF4iMzf4B1x3Yt57Yy4zK5fQpy8ukQfwX7CL+RdeEFHmBhkEyjKtFhYI0QNSyX1sPomp7V6StUyutth19off5/jnriXW4WXhB+lQ8n54NS5rQ6HDz/WzhGgX5dFNgqcQ/H8In6sgC5113z90UybCXK2mxWGx6iCYvQcC7oPn74MUHadPxdlVdqzfjerMdthswRl9PdJJUzIhaHJxyvRzYL5PQmOnpV8raPd/t54WgUjZeYcD6dcG7IIyibDA+uPMl/pt/a1CujN9EJgIby/A0O6H3gf1ffBUijqoO8 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000025, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2025/4/4 11:20, Vishal Moola (Oracle) 写道: > On Fri, Apr 04, 2025 at 07:46:59AM +1030, Qu Wenruo wrote: >> [...] >>>> Then I looked into the caller of filemap_get_folios_contig() inside >>>> mm/gup, and it indeed does the correct skip. >>> >>> ... that code looks wrong to me. >> >> It looks like it's xas_find() is doing the correct skip by calling >> xas_next_offset() -> xas_move_index() to skip the next one. >> >> But the filemap_get_folios_contig() only calls xas_next() by increasing the >> index, not really skip to the next folio. >> >> Although I can be totally wrong as I'm not familiar with the xarray >> internals at all. > > Thanks for bringing this to my attention, it looks like this is due to a > mistake during my folio conversion for this function. The xas_next() > call tries to go to the next index, but if that index is part of a > multi-index entry things get awkward if we don't manually account for the > index shift of a large folio (which I missed). > > Can you please try out this attached patch and see if it gets rid of > the duplicate problem? My reproducer no longer hang and the trace events indeed shows only one folio returned. Thanks for the quick fix, Qu > >> However I totally agree the duplicated behavior (and the extra handling of >> duplicated entries) looks very wrong. >> >> Thanks, >> Qu