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 X-Spam-Level: X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB060C63799 for ; Thu, 22 Jul 2021 16:56:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D0A246136E for ; Thu, 22 Jul 2021 16:56:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235794AbhGVQOO (ORCPT ); Thu, 22 Jul 2021 12:14:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:55310 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235045AbhGVQKe (ORCPT ); Thu, 22 Jul 2021 12:10:34 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A9EB360BD3; Thu, 22 Jul 2021 16:51:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626972669; bh=YPFjIV/cOfo9frdHbxz8MEqY64Kh1mVpesIueSZqjno=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nAXgxxdGtBBkU8sn4fROa9JZHXVZajAjmGPJtJSdY3L6/CM/2QBFUl3l7IzZxoXyj CA6ta6IH7o9hBD5w/cB6Rnus2PfnjWRLiYGZDRhXreNFdWkUFKstCejnNzXhm1Cmem GwIsywdwsq01gSQYwxaksmS32B/Uhz3YxE6d/5BupSJPnKByJuCFatZXXPl4aAmn3N Pl6Wd1nYSMYStmwtemRcGL4PMDKcLEwVVU1Y/o9RUz4027v38a3LPsD4BKGrS8uO27 xWh9Cn0jOuG0Myd+zW52DdDwL9Bu3CGrpjGl4mx+CxOaLjjIcHDk+L8WEUHCX79G0q e7bGYJzb4JQcw== Date: Thu, 22 Jul 2021 09:51:09 -0700 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Gao Xiang , linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, LKML , Matthew Wilcox , Andreas Gruenbacher Subject: Re: [PATCH v6] iomap: support tail packing inline read Message-ID: <20210722165109.GD8639@magnolia> References: <20210722031729.51628-1-hsiangkao@linux.alibaba.com> <20210722053947.GA28594@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210722053947.GA28594@lst.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 22, 2021 at 07:39:47AM +0200, Christoph Hellwig wrote: > I think some of the language here is confusing - mostly about tail > packing when we otherwise use inline data. Can you take a look at > the version below? This mostly cleans up the terminology, adds a > new helper to check the size, and removes the error on trying to > write with a non-zero pos, as it can be trivially supported now. > > --- > From 0f9c6ac6c2e372739b29195d25bebb8dd87e583a Mon Sep 17 00:00:00 2001 > From: Gao Xiang > Date: Thu, 22 Jul 2021 11:17:29 +0800 > Subject: iomap: make inline data support more flexible > > Add support for offsets into the inline data page at iomap->inline_data > to cater for the EROFS tailpackng case where a small data is stored > right after the inode. The commit message is a little misleading -- this adds support for inline data pages at nonzero (but page-aligned) file offsets, not file offsets into the page itself. I suggest: "Add support for reading inline data content into the page cache from nonzero page-aligned file offsets. This enables the EROFS tailpacking mode where the last few bytes of the file are stored right after the inode." The code changes look good to me. --D > > Signed-off-by: Gao Xiang > --- > fs/iomap/buffered-io.c | 35 ++++++++++++++++++----------------- > fs/iomap/direct-io.c | 10 ++++++---- > include/linux/iomap.h | 14 ++++++++++++++ > 3 files changed, 38 insertions(+), 21 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index 87ccb3438becd9..0597f5c186a33f 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -205,25 +205,29 @@ struct iomap_readpage_ctx { > struct readahead_control *rac; > }; > > -static void > -iomap_read_inline_data(struct inode *inode, struct page *page, > - struct iomap *iomap) > +static int iomap_read_inline_data(struct inode *inode, struct page *page, > + struct iomap *iomap, loff_t pos) > { > - size_t size = i_size_read(inode); > + size_t size = iomap->length + iomap->offset - pos; > void *addr; > > if (PageUptodate(page)) > - return; > + return PAGE_SIZE; > > - BUG_ON(page_has_private(page)); > - BUG_ON(page->index); > - BUG_ON(size > PAGE_SIZE - offset_in_page(iomap->inline_data)); > + /* inline data must start page aligned in the file */ > + if (WARN_ON_ONCE(offset_in_page(pos))) > + return -EIO; > + if (WARN_ON_ONCE(!iomap_inline_data_size_valid(iomap))) > + return -EIO; > + if (WARN_ON_ONCE(page_has_private(page))) > + return -EIO; > > addr = kmap_atomic(page); > - memcpy(addr, iomap->inline_data, size); > + memcpy(addr, iomap_inline_buf(iomap, pos), size); > memset(addr + size, 0, PAGE_SIZE - size); > kunmap_atomic(addr); > SetPageUptodate(page); > + return PAGE_SIZE; > } > > static inline bool iomap_block_needs_zeroing(struct inode *inode, > @@ -246,11 +250,8 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > unsigned poff, plen; > sector_t sector; > > - if (iomap->type == IOMAP_INLINE) { > - WARN_ON_ONCE(pos); > - iomap_read_inline_data(inode, page, iomap); > - return PAGE_SIZE; > - } > + if (iomap->type == IOMAP_INLINE) > + return iomap_read_inline_data(inode, page, iomap, pos); > > /* zero post-eof blocks as the page may be mapped */ > iop = iomap_page_create(inode, page); > @@ -618,14 +619,14 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags, > } > > if (srcmap->type == IOMAP_INLINE) > - iomap_read_inline_data(inode, page, srcmap); > + status = iomap_read_inline_data(inode, page, srcmap, pos); > else if (iomap->flags & IOMAP_F_BUFFER_HEAD) > status = __block_write_begin_int(page, pos, len, NULL, srcmap); > else > status = __iomap_write_begin(inode, pos, len, flags, page, > srcmap); > > - if (unlikely(status)) > + if (unlikely(status < 0)) > goto out_unlock; > > *pagep = page; > @@ -675,7 +676,7 @@ static size_t iomap_write_end_inline(struct inode *inode, struct page *page, > > flush_dcache_page(page); > addr = kmap_atomic(page); > - memcpy(iomap->inline_data + pos, addr + pos, copied); > + memcpy(iomap_inline_buf(iomap, pos), addr + pos, copied); > kunmap_atomic(addr); > > mark_inode_dirty(inode); > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 9398b8c31323b3..a6aaea2764a55f 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -378,23 +378,25 @@ iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length, > struct iomap_dio *dio, struct iomap *iomap) > { > struct iov_iter *iter = dio->submit.iter; > + void *dst = iomap_inline_buf(iomap, pos); > size_t copied; > > - BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data)); > + if (WARN_ON_ONCE(!iomap_inline_data_size_valid(iomap))) > + return -EIO; > > if (dio->flags & IOMAP_DIO_WRITE) { > loff_t size = inode->i_size; > > if (pos > size) > - memset(iomap->inline_data + size, 0, pos - size); > - copied = copy_from_iter(iomap->inline_data + pos, length, iter); > + memset(iomap_inline_buf(iomap, size), 0, pos - size); > + copied = copy_from_iter(dst, length, iter); > if (copied) { > if (pos + copied > size) > i_size_write(inode, pos + copied); > mark_inode_dirty(inode); > } > } else { > - copied = copy_to_iter(iomap->inline_data + pos, length, iter); > + copied = copy_to_iter(dst, length, iter); > } > dio->size += copied; > return copied; > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 479c1da3e2211e..5efae7153912ed 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -97,6 +97,20 @@ iomap_sector(struct iomap *iomap, loff_t pos) > return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT; > } > > +static inline void *iomap_inline_buf(const struct iomap *iomap, loff_t pos) > +{ > + return iomap->inline_data - iomap->offset + pos; > +} > + > +/* > + * iomap->inline_data is a potentially kmapped page, ensure it never crosseѕ a > + * page boundary. > + */ > +static inline bool iomap_inline_data_size_valid(const struct iomap *iomap) > +{ > + return iomap->length <= PAGE_SIZE - offset_in_page(iomap->inline_data); > +} > + > /* > * When a filesystem sets page_ops in an iomap mapping it returns, page_prepare > * and page_done will be called for each page written to. This only applies to > -- > 2.30.2 >