On 23:22 Sun 16 Mar , Andreas Dilger wrote: > On Mar 16, 2008 14:39 +0300, Dmitri Monakhov wrote: > > > --- linux-2.6.24/fs/namei.c.orig 2008-02-05 07:29:57.000000000 +0800 > > > +++ linux-2.6.24/fs/namei.c 2008-03-16 08:11:41.000000000 +0800 > > > @@ -233,6 +233,10 @@ int permission(struct inode *inode, int > > > if (nd) > > > mnt = nd->mnt; > > > > > > + /* Don't allow direct read, write, or truncate on a swapfile */ > > > > Your patch disallow expand truncates (#2) which is definitely not good. > > How often is that done though? Since this is only for a swapfile then > it isn't needed. I hope what this technique may be used for implementing non plain device image formats support in loop device driver, currently all such drivers implemented in userspace ( for example qcow: http://brick.kernel.dk/git/?p=qemu.git;a=blob;h=730ae67ed8f7095ca4d22e80aca57678be18fb6c;hb=2fd2f67411787297687e4eecbb1db76ac7d06e45;f=block-qcow.c) which cause bad performance and reliability. > > > In fact if file was opened before S_SWAPFILE flag was setted when it is > > possible to directly read, write from file. > > I assume that is even a more rare case. I was thinking alternately to > do a "deny_write" on the swapfile during swapon() so that this would > fail in more cases. > > > > + if (IS_SWAPFILE(inode)) > > > + return -ETXTBUSY; > > > + > > > if (mask & MAY_WRITE) { > > > umode_t mode = inode->i_mode; > > > > BTW it is impossible to disable swapfile with your patch > > [root@ts63 tmp]# swapoff /vz/swap > > swapoff: /vz/swap: Text file busy > > I thought some bug like this might appear. > > > IMHO S_SWAPFILE flag must be checked in ext3_setattr, see patch attached: > > No, that still means every other filesystem is broken. Since the current > filesystem code doesn't know anything about IS_SWAPFILE I'd rather keep > it that way. I think it is better to move my proposed IS_SWAPFILE() check > into "MAY_WRITE" and "MAY_EXEC" cases. > > Cheers, Andreas > -- > Andreas Dilger > Sr. Staff Engineer, Lustre Group > Sun Microsystems of Canada, Inc. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
