On Tue, 22 Jan 2013 14:44:00 +0100, Jan Kara <jack@xxxxxxx> wrote:
> On Tue 22-01-13 15:11:24, Dmitry Monakhov wrote:
> > On Fri, 18 Jan 2013 13:00:37 +0100, Jan Kara <jack@xxxxxxx> wrote:
> > > When using indirect blocks there is no possibility to have any unwritten
> > > extents. So wait for them in ext4_ind_direct_IO() is just bogus.
> > But as soon as i remember indirect implementation may also be used by
> > extents based inodes 3074: ext4_ext_direct_IO
> > /* Use the old path for reads and writes beyond i_size. */
> > if (rw != WRITE || final_size > inode->i_size)
> > return ext4_ind_direct_IO(rw, iocb, iov, offset, nr_segs);
> >
> > Am I missing ?
> Ah, that's a catch. Thanks for pointing that out! So my patch is wrong
> and that code path needs some cleaning and commenting. In particular I'm
> afraid using dioread_nolock for inodes with indirect map causes data
> exposure bugs when unlocked DIO read races with DIO write because such
> inodes don't support uninitialized extents.
Yes that's why dioread_nolock works only for extent based inodes
static inline int ext4_should_dioread_nolock(struct inode *inode)
{
if (!test_opt(inode->i_sb, DIOREAD_NOLOCK))
return 0;
if (!S_ISREG(inode->i_mode))
return 0;
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
return 0;
if (ext4_should_journal_data(inode))
return 0;
return 1;
}
>
> Honza
> --
> Jan Kara <jack@xxxxxxx>
> SUSE Labs, CR
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