From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DE94C47073 for ; Thu, 4 Jan 2024 00:22:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 443AA6B030F; Wed, 3 Jan 2024 19:22:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3F3756B0310; Wed, 3 Jan 2024 19:22:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E3A06B0311; Wed, 3 Jan 2024 19:22:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 1D82A6B030F for ; Wed, 3 Jan 2024 19:22:04 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id F26424011D for ; Thu, 4 Jan 2024 00:22:03 +0000 (UTC) X-FDA: 81639726126.22.6D09252 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf28.hostedemail.com (Postfix) with ESMTP id F0147C0010 for ; Thu, 4 Jan 2024 00:22:01 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=pGSwdFTX; spf=pass (imf28.hostedemail.com: domain of djwong@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=djwong@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1704327722; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=a2YW2LdEnLYy7XVko1wX+hLIeM0Od54B4aWpKmWAfsw=; b=EMlcLB7AYksJNEiQViWDjJzUBC0Ko1o5x8MkZ5LhYtAv4L4ytSzrrbrJ+AKj4NUNycnB89 TmJ54WKQG+RI1ph1OH6Jt9a/JLJxP0VpI6bsIyX7qmt6+ZdDBxdaZInXSla6MtygdwfdT3 y8QzxtiuAkV5skz88u7X8L36mGzaECE= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=pGSwdFTX; spf=pass (imf28.hostedemail.com: domain of djwong@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=djwong@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1704327722; a=rsa-sha256; cv=none; b=AHGFqSaYY2OJDdbSQYH+D7A2V1E0wJxpnK10vQHCUuLM91CzGU7LFJ4QJ7RLxaQsRLYw72 McsiQCgO7CiCkJVUXin/FTbI4DuFO2tQneQCumQvrNuzDtRGzZD/b/dk6bm6NRC68ek3ci NTakpucEfMQ69bdC8w/vJjgPphddksY= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 456BACE13A2; Thu, 4 Jan 2024 00:21:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B539C433C8; Thu, 4 Jan 2024 00:21:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1704327718; bh=sInAZji0FgjBKb4Yg/f4gvF7/RXfJasa60oS1R36FQU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pGSwdFTXhqNtFGWhMvAYB5ce6FKfmkuTGZphlTfkekv7jzaVqQl4uXBrWOWxunn9W 9AsRBJJqAXcDicDuOmDleocDUkButJjBfYvvHKAJq9f1uF8/Fg+IvuSu5Ty0pkWSWF vMqTOX7Q/An/nwCTCMiQWNkxsnEzLvIKR3t0rWEcfdCCOvpjmMUxkEvhqZHDCw2Lf4 JHkyU1voQDa/hcjglEVVCHucGfMBefvHa4FYxGzXgHx2rd1ewmKanrqtbqysOS1BWq EPFfu5qHX5XnwB26ddaf9UmjMxxuTVXV3iAEfCtQJFZ0jKLCLyBz5AogSqzwLwj3SF q4OO0SJyHqzmQ== Date: Wed, 3 Jan 2024 16:21:58 -0800 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Chandan Babu R , Hugh Dickins , Andrew Morton , linux-xfs@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 03/15] shmem: document how to "persist" data when using shmem_*file_setup Message-ID: <20240104002158.GJ361584@frogsfrogsfrogs> References: <20240103084126.513354-1-hch@lst.de> <20240103084126.513354-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240103084126.513354-4-hch@lst.de> X-Rspamd-Queue-Id: F0147C0010 X-Rspam-User: X-Stat-Signature: ikxk3kdf8cajn86uz1gi883zq83bnufe X-Rspamd-Server: rspam01 X-HE-Tag: 1704327721-797715 X-HE-Meta: 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 slJA6fiO ZG1BjuoGRYo1TY33jhcFv0dkLqLgMHTrL6/N/ZlDfiiWTL2djBu1bQuRl5HscnNWd2GAtLtwGFmBV0KMJ6KfTDzqWsLIqogv5QNSiLIqk9SQQh60AQEdR+pgh/p9dN7QTrQ2Az8Uhf7uwDjAPWQTae/OE1Z2y1SpvbnYLwMB2EK8LgP5e0+tjH3iuY2Jd8aAFFImIjENNvrW7J5gL02KbK+OvSRuFE5k57aGiI5ZWT2R3O+E= 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: List-Subscribe: List-Unsubscribe: On Wed, Jan 03, 2024 at 08:41:14AM +0000, Christoph Hellwig wrote: > Add a blurb that simply dirtying the folio will persist data for in-kernel > shmem files. This is what most of the callers already do. > > Signed-off-by: Christoph Hellwig > --- > mm/shmem.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/shmem.c b/mm/shmem.c > index 328eb3dbea9f1c..235fac6dc53a0b 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2129,6 +2129,11 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, > * > * Return: The found folio, %NULL if SGP_READ or SGP_NOALLOC was passed in @sgp > * and no folio was found at @index, or an ERR_PTR() otherwise. > + * > + * If the caller modifies data in the returned folio, it must call > + * folio_mark_dirty() on the locked folio before dropping the reference to > + * ensure the folio is not reclaimed. Unlike for normal file systems there is > + * no need to reserve space for users of shmem_*file_setup(). /me notes that this matches how /I/ think this is supposed to work, but I think someone more familiar with tmpfs should review this... --D > */ > int shmem_get_folio(struct inode *inode, pgoff_t index, struct folio **foliop, > enum sgp_type sgp) > -- > 2.39.2 > >