From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <457D512F.3020605@sw.ru> Date: Mon, 11 Dec 2006 15:38:07 +0300 From: Kirill Korotaev MIME-Version: 1.0 Subject: Re: [Devel] [PATCH] incorrect error handling inside generic_file_direct_write References: <87k60y1rq4.fsf@sw.ru> In-Reply-To: <87k60y1rq4.fsf@sw.ru> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Linux Memory Management , devel@openvz.org, Monakhov Dmintiy List-ID: I guess you forgot to add Andrew on CC. Thanks, Kirill > OpenVZ team has discovered error inside generic_file_direct_write() > If generic_file_direct_IO() has fail (ENOSPC condition) it may have instantiated > a few blocks outside i_size. And fsck will complain about wrong i_size > (ext2, ext3 and reiserfs interpret i_size and biggest block difference as error), > after fsck will fix error i_size will be increased to the biggest block, > but this blocks contain gurbage from previous write attempt, this is not > information leak, but its silence file data corruption. > We need truncate any block beyond i_size after write have failed , do in simular > generic_file_buffered_write() error path. > > Exampe: > open("mnt2/FILE3", O_WRONLY|O_CREAT|O_DIRECT, 0666) = 3 > write(3, "aaaaaa"..., 4096) = -1 ENOSPC (No space left on device) > > stat mnt2/FILE3 > File: `mnt2/FILE3' > Size: 0 Blocks: 4 IO Block: 4096 regular empty file > >>>>>>>>>>>>>>>>>>>>>>>^^^^^^^^^^ file size is less than biggest block idx > > Device: 700h/1792d Inode: 14 Links: 1 > Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) > > fsck.ext2 -f -n mnt1/fs_img > Pass 1: Checking inodes, blocks, and sizes > Inode 14, i_size is 0, should be 2048. Fix? no > > Signed-off-by: Dmitriy Monakhov > ---------- > > > ------------------------------------------------------------------------ > > diff --git a/mm/filemap.c b/mm/filemap.c > index 7b84dc8..bf7cf6c 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2041,6 +2041,14 @@ generic_file_direct_write(struct kiocb * > mark_inode_dirty(inode); > } > *ppos = end; > + } else if (written < 0) { > + loff_t isize = i_size_read(inode); > + /* > + * generic_file_direct_IO() may have instantiated a few blocks > + * outside i_size. Trim these off again. > + */ > + if (pos + count > isize) > + vmtruncate(inode, isize); > } > > /* > > > ------------------------------------------------------------------------ > > _______________________________________________ > Devel mailing list > Devel@openvz.org > https://openvz.org/mailman/listinfo/devel -- 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