Re: [Ext2-devel] Re: [RFD] FS behavior (I/O failure) in kernel summit

[Matthew Wilcox <matthew@wil.cx>]

On Wed, Jun 15, 2005 at 10:01:05AM -0400, Theodore Ts'o wrote:
> We can only return EIO or EROFS.  And while the write()
> which causes an I/O error that remounts the filesystem read/only can
> (and probably does) return EIO, any subsequent writes will return
> EROFS, and changing this would be hard, hackish, and probably wouldn't
> be accepted.

I wasn't quite sure why this would be so hard, so I took a look.  Here's
how it works:

In fs/ext2/super.c, we do:
        if (test_opt(sb, ERRORS_RO)) {
                printk("Remounting filesystem read-only\n");
                sb->s_flags |= MS_RDONLY;
        }

>From here on, the VFS handles returning -EROFS (except for a couple
of ioctls and an xattr call).  So it's not under the control of the
individual filesystem.  One way of handling this would be to introduce a
new MS_ERRORS flag that allows the VFS to return -EIO instead of -EROFS
for a filesystem that contains errors.

-- 
"Next the statesmen will invent cheap lies, putting the blame upon 
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince 
himself that the war is just, and will thank God for the better sleep 
he enjoys after this process of grotesque self-deception." -- Mark Twain