From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id CA9AA6B003D for ; Tue, 10 Mar 2009 23:55:06 -0400 (EDT) Date: Wed, 11 Mar 2009 04:55:03 +0100 From: Nick Piggin Subject: [patch 2/2] fs: fix page_mkwrite error cases in core code and btrfs Message-ID: <20090311035503.GI16561@wotan.suse.de> References: <20090311035318.GH16561@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090311035318.GH16561@wotan.suse.de> Sender: owner-linux-mm@kvack.org To: Andrew Morton , linux-fsdevel@vger.kernel.org, Linux Memory Management List , Chris Mason List-ID: page_mkwrite is called with neither the page lock nor the ptl held. This means a page can be concurrently truncated or invalidated out from underneath it. Callers are supposed to prevent truncate races themselves, however previously the only thing they can do in case they hit one is to raise a SIGBUS. A sigbus is wrong for the case that the page has been invalidated or truncated within i_size (eg. hole punched). Callers may also have to perform memory allocations in this path, where again, SIGBUS would be wrong. The previous patch made it possible to properly specify errors. Convert the generic buffer.c code and btrfs to return sane error values (in the case of page removed from pagecache, VM_FAULT_NOPAGE will cause the fault handler to exit without doing anything, and the fault will be retried properly). This fixes core code, and converts btrfs as a template/example. All other filesystems defining their own page_mkwrite should be fixed in a similar manner. Acked-by: Chris Mason Signed-off-by: Nick Piggin --- fs/btrfs/inode.c | 11 +++++++---- fs/buffer.c | 12 ++++++++---- 2 files changed, 15 insertions(+), 8 deletions(-) Index: linux-2.6/fs/btrfs/inode.c =================================================================== --- linux-2.6.orig/fs/btrfs/inode.c +++ linux-2.6/fs/btrfs/inode.c @@ -4307,10 +4307,15 @@ int btrfs_page_mkwrite(struct vm_area_st u64 page_end; ret = btrfs_check_data_free_space(root, inode, PAGE_CACHE_SIZE); - if (ret) + if (ret) { + if (ret == -ENOMEM) + ret = VM_FAULT_OOM; + else /* -ENOSPC, -EIO, etc */ + ret = VM_FAULT_SIGBUS; goto out; + } - ret = -EINVAL; + ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */ again: lock_page(page); size = i_size_read(inode); @@ -4363,8 +4368,6 @@ again: out_unlock: unlock_page(page); out: - if (ret) - ret = VM_FAULT_SIGBUS; return ret; } Index: linux-2.6/fs/buffer.c =================================================================== --- linux-2.6.orig/fs/buffer.c +++ linux-2.6/fs/buffer.c @@ -2473,7 +2473,7 @@ block_page_mkwrite(struct vm_area_struct struct inode *inode = vma->vm_file->f_path.dentry->d_inode; unsigned long end; loff_t size; - int ret = -EINVAL; + int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */ lock_page(page); size = i_size_read(inode); @@ -2493,10 +2493,14 @@ block_page_mkwrite(struct vm_area_struct if (!ret) ret = block_commit_write(page, 0, end); -out_unlock: - if (ret) - ret = VM_FAULT_SIGBUS; + if (unlikely(ret)) { + if (ret == -ENOMEM) + ret = VM_FAULT_OOM; + else /* -ENOSPC, -EIO, etc */ + ret = VM_FAULT_SIGBUS; + } +out_unlock: unlock_page(page); return ret; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org