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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.0.3 Subject: Re: [PATCH v4] mm/page_owner.c: add llseek for page_owner Content-Language: en-US To: Kassey Li , akpm@linux-foundation.org Cc: minchan@kernel.org, iamjoonsoo.kim@lge.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20220808073606.29666-1-quic_yingangl@quicinc.com> From: "Vlastimil Babka (SUSE)" In-Reply-To: <20220808073606.29666-1-quic_yingangl@quicinc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="W/LlGgb5"; spf=pass (imf31.hostedemail.com: domain of vbabka@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1659972806; a=rsa-sha256; cv=none; b=OqKngWA7WEUiUatin0NvCYeQ7hkLSWiK7N2mYwLRmvq39ujauEQzqT1hoA5g8XI37FtIYH JbBQPudQGnkGRezPPpJmFzlQ3mjpmT7ZBdKsAJFLJnmtVSqL91hhFxVM8LSVK9PnqoQEFP 0DW5CkusRr7KeAyeESDtCIXT0TrFx6U= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1659972806; h=from:from:sender:reply-to:subject:subject: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:dkim-signature; bh=wsJaLaYlq/RhyDLlLZ7mNtptS9466wMAg5miAsAbQUI=; b=7ABOq5B1DgUiZrS0fimsQYvwhJGZewsvj2u46EqP62zZLuXDO02dJQRcZj+IhWG2KLhjFx DIsKMryAQOSAhSTHDrVeVSGHb1ZmLwVwaY5aFLgWis2+owtg8Me+KQndafepVOyDTdIco6 f9+bRXr6ohcQdm3dMkJNw8BktS2acdY= X-Stat-Signature: eo1wa3qhzzn394igpzws8tnnukqhpdzz X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 68DBC20164 Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b="W/LlGgb5"; spf=pass (imf31.hostedemail.com: domain of vbabka@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-HE-Tag: 1659972806-974062 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: On 8/8/22 09:36, Kassey Li wrote: > There is usage to dump a given cma region page_owner > instead of all page's. > > This change allows to specify a ppos as start_pfn > by fseek. > > Any invalid ppos will be skipped, so it did not > broken the origin dump feature. > > Suggested-by: Vlastimil Babka (SUSE) Thanks, but please change it to Vlastimil Babka It was some mistake between me and thunderbird that it was sent from @k.o. > Signed-off-by: Kassey Li > --- > mm/page_owner.c | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index e4c6f3f1695b..231b1877af99 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -497,8 +497,8 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) > return -EINVAL; > > page = NULL; > - pfn = min_low_pfn + *ppos; > > + pfn = *ppos; Maybe we could still optimize the typical case a bit such that when it's 0, we skip to min_low_pfn immediately. > /* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */ > while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0) > pfn++; > @@ -561,7 +561,7 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) > continue; > > /* Record the next PFN to read in the file offset */ > - *ppos = (pfn - min_low_pfn) + 1; > + *ppos = pfn + 1; > > return print_page_owner(buf, count, pfn, page, > page_owner, handle); > @@ -570,6 +570,21 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) > return 0; > } > > +static loff_t llseek_page_owner(struct file *file, loff_t offset, int whence) > +{ > + loff_t retval = 0; > + switch (whence) { > + case SEEK_CUR: It's not correct for SEEK_CUR to behave like this, no? Can we perhaps reuse the existing mem_lseek() ? Also we should update Documentation/mm/page_owner.rst to document the lseek support and that it works with a pfn. Thanks! > + case SEEK_SET: > + file->f_pos = offset; > + break; > + default: > + retval = -ENXIO; > + } > + > + return retval; > +} > + > static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone) > { > unsigned long pfn = zone->zone_start_pfn; > @@ -660,6 +675,7 @@ static void init_early_allocated_pages(void) > > static const struct file_operations proc_page_owner_operations = { > .read = read_page_owner, > + .llseek = llseek_page_owner, > }; > > static int __init pageowner_init(void)