Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757678AbYGZW3W (ORCPT ); Sat, 26 Jul 2008 18:29:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753352AbYGZW3O (ORCPT ); Sat, 26 Jul 2008 18:29:14 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:52778 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753047AbYGZW3N (ORCPT ); Sat, 26 Jul 2008 18:29:13 -0400 Date: Sat, 26 Jul 2008 23:28:32 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.site To: Kel Modderman cc: Andrew Morton , Alexey Dobriyan , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: tmpfs: kernel BUG at mm/shmem.c:814 In-Reply-To: <200807262210.11502.kel@otaku42.de> Message-ID: References: <200807262210.11502.kel@otaku42.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2770 Lines: 65 On Sat, 26 Jul 2008, Kel Modderman wrote: > > I am able to reproduce the triggering of BUG_ON() in shmem_delete_inode > function of mm/shmem.c, line 814, while testing the insserv program in a dir > on a tmpfs mount point with Linux 2.6.25.x and 2.6.26. Outstanding bug report and steps to reproduce: thank you so much. You should find this fixes it; though we may have some more work to do, maybe other filesystems are surprised by readahead on directories. [PATCH] tmpfs: fix kernel BUG in shmem_delete_inode SuSE's insserve initscript ordering program hits kernel BUG at mm/shmem.c:814 on 2.6.26. It's using posix_fadvise on directories, and the shmem_readpage method added in 2.6.23 is letting POSIX_FADV_WILLNEED allocate useless pages to a tmpfs directory, incrementing i_blocks count but never decrementing it. Fix this by assigning shmem_aops (pointing to readpage and writepage and set_page_dirty) only when it's needed, on a regular file or a long symlink. Many thanks to Kel for outstanding bugreport and steps to reproduce it. Reported-by: Kel Modderman Signed-off-by: Hugh Dickins Cc: stable@kernel.org --- Other filesystems... ramfs looks as if it would allocate useless pages too, but should free them, and wouldn't BUG; are there other filesystems to be surprised by readahead on directories? I have not looked through yet. mm/shmem.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- 2.6.26-git/mm/shmem.c 2008-07-26 12:33:28.000000000 +0100 +++ linux/mm/shmem.c 2008-07-26 22:46:28.000000000 +0100 @@ -1513,7 +1513,6 @@ shmem_get_inode(struct super_block *sb, inode->i_uid = current->fsuid; inode->i_gid = current->fsgid; inode->i_blocks = 0; - inode->i_mapping->a_ops = &shmem_aops; inode->i_mapping->backing_dev_info = &shmem_backing_dev_info; inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; inode->i_generation = get_seconds(); @@ -1528,6 +1527,7 @@ shmem_get_inode(struct super_block *sb, init_special_inode(inode, mode, dev); break; case S_IFREG: + inode->i_mapping->a_ops = &shmem_aops; inode->i_op = &shmem_inode_operations; inode->i_fop = &shmem_file_operations; mpol_shared_policy_init(&info->policy, @@ -1929,6 +1929,7 @@ static int shmem_symlink(struct inode *d return error; } unlock_page(page); + inode->i_mapping->a_ops = &shmem_aops; inode->i_op = &shmem_symlink_inode_operations; kaddr = kmap_atomic(page, KM_USER0); memcpy(kaddr, symname, len); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/