On Tue 22-01-13 18:12:38, Dmitry Monakhov wrote:
> 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;
> }
Sure, I was confused. Things work correctly just the code flow is a bit
confusing.
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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