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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6AA0C77B71 for ; Sat, 15 Apr 2023 02:32:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230209AbjDOCcG (ORCPT ); Fri, 14 Apr 2023 22:32:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229463AbjDOCcE (ORCPT ); Fri, 14 Apr 2023 22:32:04 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66B2D59D2; Fri, 14 Apr 2023 19:32:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=LKu44/7divD7drUoUvhwbQweIThwjY6Ox0fiwkad+8M=; b=jkOcp4tWYw5Dep25AqfvxqhTc4 GTCA3dP1WQgfymf/IooR40z7GLI6DLMgaeBasOvQVaaWYSmM4lh4dDW2fLel82NDzIZ54rPbUdBzF xGvbNAmM5pdLlIE7sS9cxobQ9+7HClxopbNumnWDoEVWsA1Vh7b4iYmCT4yTIIRJSWCY67XcTm4rR OxkafstpetKZvyEgWnM6lI1eEnlJ9+3hnMMXhm9n33RXXVT/l6PuA/Feqhjg1Xp4msf5SKcdVyT4F VFOYthuGpidWVrHCEv54eK76yMlcnMoa8POrsHHhRZlL6Ar004znok/fKBak7xVhndNnL5tNnqVsF 1/RCzSfg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pnVhi-009Hpb-FL; Sat, 15 Apr 2023 02:31:54 +0000 Date: Sat, 15 Apr 2023 03:31:54 +0100 From: Matthew Wilcox To: Luis Chamberlain Cc: Hannes Reinecke , Pankaj Raghav , brauner@kernel.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, gost.dev@samsung.com Subject: Re: [RFC 0/4] convert create_page_buffers to create_folio_buffers Message-ID: References: <20230414110821.21548-1-p.raghav@samsung.com> <1e68a118-d177-a218-5139-c8f13793dbbf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 14, 2023 at 06:01:16PM -0700, Luis Chamberlain wrote: > a) dynamically allocate those now > b) do a cursory review of the users of that and prepare them > to grok buffer heads which are blocksize based rather than > PAGE_SIZE based. So we just try to kill MAX_BUF_PER_PAGE. > > Without a) I think buffers after PAGE_SIZE won't get submit_bh() or lock for > bs > PAGE_SIZE right now. Worse, we'll overflow the array and corrupt the stack. This one is a simple fix ... +++ b/fs/buffer.c @@ -2282,7 +2282,7 @@ int block_read_full_folio(struct folio *folio, get_block_t *get_block) { struct inode *inode = folio->mapping->host; sector_t iblock, lblock; - struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; + struct buffer_head *bh, *head; unsigned int blocksize, bbits; int nr, i; int fully_mapped = 1; @@ -2335,7 +2335,6 @@ int block_read_full_folio(struct folio *folio, get_block_t *get_block) if (buffer_uptodate(bh)) continue; } - arr[nr++] = bh; } while (i++, iblock++, (bh = bh->b_this_page) != head); if (fully_mapped) @@ -2353,24 +2352,27 @@ int block_read_full_folio(struct folio *folio, get_block_t *get_block) } /* Stage two: lock the buffers */ - for (i = 0; i < nr; i++) { - bh = arr[i]; + bh = head; + do { lock_buffer(bh); mark_buffer_async_read(bh); - } + bh = bh->b_this_page; + } while (bh != head); /* * Stage 3: start the IO. Check for uptodateness * inside the buffer lock in case another process reading * the underlying blockdev brought it uptodate (the sct fix). */ - for (i = 0; i < nr; i++) { - bh = arr[i]; + bh = head; + do { if (buffer_uptodate(bh)) end_buffer_async_read(bh, 1); else submit_bh(REQ_OP_READ, bh); - } + bh = bh->b_this_page; + } while (bh != head); + return 0; } EXPORT_SYMBOL(block_read_full_folio);