From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261310AbULWVio (ORCPT ); Thu, 23 Dec 2004 16:38:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261311AbULWVio (ORCPT ); Thu, 23 Dec 2004 16:38:44 -0500 Received: from 10fwd.cistron-office.nl ([62.216.29.197]:44758 "EHLO smtp.cistron-office.nl") by vger.kernel.org with ESMTP id S261310AbULWVib (ORCPT ); Thu, 23 Dec 2004 16:38:31 -0500 From: "Miquel van Smoorenburg" To: mason@suse.com Subject: Re: [PATCH] __getblk_slow can loop forever when pages are partially mapped X-Newsgroups: lists.linux.kernel In-Reply-To: <1102711728.4957.159.camel@watt.suse.com> Organization: Cistron Group Cc: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Message-Id: Date: Thu, 23 Dec 2004 22:38:14 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In article <1102711728.4957.159.camel@watt.suse.com> you write: >When a block device is accessed via read/write, it is possible >for some of the buffers on a page to be mapped and others not. __getblk >and friends assume this can't happen, and can end up looping forever >when pages have some unmapped buffers. > >The fix below has two parts. First, it changes __find_get_block >to avoid the buffer_error warnings when it finds unmapped buffers >on the page. > >Second, it changes grow_dev_page to map the buffers on the page >by calling init_page_buffers. init_page_buffers is changed so >we don't stomp on uptodate bits for the buffers I just upgraded a server with a 2.4.22 kernel and blocksize 1K ext2 filesystems to 2.6.10-rc3. Before I rebooted, I did a "tune2fs -j /dev/hda1" (etc) to move from ext2 to ext3 on /, /usr, /var and /home. When the new kernel was supposed to mount the root filesystem, it kept on spewing the message Blocksize 1024 __getblk_slow failed I booted back to 2.4.22, applied the patch below, booted to 2.6.10-rc3 + patch, and now it's running just fine. I don't see anything like the patch below in 2.6.10-rc3-bk16 yet ? >Index: linux.mm/fs/buffer.c >=================================================================== >--- linux.mm.orig/fs/buffer.c 2004-12-10 09:44:34.000000000 -0500 >+++ linux.mm/fs/buffer.c 2004-12-10 11:22:23.000000000 -0500 >@@ -426,6 +426,7 @@ __find_get_block_slow(struct block_devic > struct buffer_head *bh; > struct buffer_head *head; > struct page *page; >+ int all_mapped = 1; > > index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); > page = find_get_page(bd_mapping, index); >@@ -443,14 +444,23 @@ __find_get_block_slow(struct block_devic > get_bh(bh); > goto out_unlock; > } >+ if (!buffer_mapped(bh)) >+ all_mapped = 0; > bh = bh->b_this_page; > } while (bh != head); > >- printk("__find_get_block_slow() failed. " >- "block=%llu, b_blocknr=%llu\n", >- (unsigned long long)block, (unsigned long long)bh->b_blocknr); >- printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size); >- printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); >+ /* we might be here because some of the buffers on this page are >+ * not mapped. This is due to various races between >+ * file io on the block device and getblk. It gets dealt with >+ * elsewhere, don't buffer_error if we had some unmapped buffers >+ */ >+ if (all_mapped) { >+ printk("__find_get_block_slow() failed. " >+ "block=%llu, b_blocknr=%llu\n", >+ (unsigned long long)block, (unsigned long long)bh->b_blocknr); >+ printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size); >+ printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); >+ } > out_unlock: > spin_unlock(&bd_mapping->private_lock); > page_cache_release(page); >@@ -1098,18 +1108,16 @@ init_page_buffers(struct page *page, str > { > struct buffer_head *head = page_buffers(page); > struct buffer_head *bh = head; >- unsigned int b_state; >- >- b_state = 1 << BH_Mapped; >- if (PageUptodate(page)) >- b_state |= 1 << BH_Uptodate; >+ int uptodate = PageUptodate(page); > > do { >- if (!(bh->b_state & (1 << BH_Mapped))) { >+ if (!buffer_mapped(bh)) { > init_buffer(bh, NULL, NULL); > bh->b_bdev = bdev; > bh->b_blocknr = block; >- bh->b_state = b_state; >+ if (uptodate) >+ set_buffer_uptodate(bh); >+ set_buffer_mapped(bh); > } > block++; > bh = bh->b_this_page; >@@ -1138,8 +1146,10 @@ grow_dev_page(struct block_device *bdev, > > if (page_has_buffers(page)) { > bh = page_buffers(page); >- if (bh->b_size == size) >+ if (bh->b_size == size) { >+ init_page_buffers(page, bdev, block, size); > return page; >+ } > if (!try_to_free_buffers(page)) > goto failed; > } > >