On Sun 09-09-12 21:27:10, Dmitry Monakhov wrote:
> Inode's block defrag and ext4_change_inode_journal_flag() may
> affect nonlocked DIO reads result, so proper synchronization
> required.
>
> - Add missed inode_dio_wait() calls where appropriate
> - Check inode state under extra i_dio_count reference.
>
> Changes from V1:
> - add missed memory bariers
> - move DIOREAD_LOCK state check out from generic should_dioread_nolock
> otherwise it will affect existing DIO readers.
Looks good. Just maybe I would rename ext4_inode_dio_wait() to
ext4_inode_block_unlocked_dio(). Anyway you can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> ---
> fs/ext4/ext4.h | 3 +++
> fs/ext4/indirect.c | 23 +++++++++++++++++++++++
> fs/ext4/inode.c | 4 ++++
> fs/ext4/move_extent.c | 5 +++++
> 4 files changed, 35 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index be976ca..0377d2b 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1348,6 +1348,8 @@ enum {
> EXT4_STATE_DIO_UNWRITTEN, /* need convert on dio done*/
> EXT4_STATE_NEWENTRY, /* File just added to dir */
> EXT4_STATE_DELALLOC_RESERVED, /* blks already reserved for delalloc */
> + EXT4_STATE_DIOREAD_LOCK, /* Disable support for dio read
> + nolocking */
> };
>
> #define EXT4_INODE_BIT_FNS(name, field, offset) \
> @@ -2015,6 +2017,7 @@ extern void ext4_da_update_reserve_space(struct inode *inode,
> /* indirect.c */
> extern int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
> struct ext4_map_blocks *map, int flags);
> +extern void ext4_inode_dio_wait(struct inode *inode, int resume);
> extern ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
> const struct iovec *iov, loff_t offset,
> unsigned long nr_segs);
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 61f13e5..3714413 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -760,6 +760,19 @@ out:
> return err;
> }
>
> +/* Wait for existing dio workers
> + * Disable DIO read nolock optimization, so new dioreaders will
> + * be forced to grab i_mutex
> +*/
> +void ext4_inode_dio_wait(struct inode *inode, int resume_readers)
> +{
> + ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> + smp_mb();
> + inode_dio_wait(inode);
> + if (resume_readers)
> + ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> +}
> +
> /*
> * O_DIRECT for ext3 (or indirect map) based files
> *
> @@ -810,10 +823,20 @@ retry:
> if (unlikely(!list_empty(&ei->i_completed_io_list)))
> ext4_flush_completed_IO(inode);
>
> + /* Nolock dioread optimization may be dynamically disabled.
> + * Check inode's state while holding extra i_dio_count ref. */
> + atomic_inc(&inode->i_dio_count);
> + smp_mb();
> + if (!unlikely(ext4_test_inode_state(inode,
> + EXT4_STATE_DIOREAD_LOCK))) {
> + inode_dio_done(inode);
> + goto retry;
> + }
> ret = __blockdev_direct_IO(rw, iocb, inode,
> inode->i_sb->s_bdev, iov,
> offset, nr_segs,
> ext4_get_block, NULL, NULL, 0);
> + inode_dio_done(inode);
> } else {
> ret = blockdev_direct_IO(rw, iocb, inode, iov,
> offset, nr_segs, ext4_get_block);
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 762b955..ffb4a27 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4720,6 +4720,9 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
> return err;
> }
>
> + /* Wait for all existing dio workers */
> + ext4_inode_dio_wait(inode, 0);
> +
> jbd2_journal_lock_updates(journal);
>
> /*
> @@ -4739,6 +4742,7 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
> ext4_set_aops(inode);
>
> jbd2_journal_unlock_updates(journal);
> + ext4_clear_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
>
> /* Finally we can mark the inode as dirty. */
>
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index c5826c6..aea0e7a 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -1214,6 +1214,9 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
> if (ret1 < 0)
> return ret1;
>
> + /* Wait for all existing dio workers */
> + ext4_inode_dio_wait(orig_inode, 0);
> + ext4_inode_dio_wait(donor_inode, 0);
> /* Protect extent tree against block allocations via delalloc */
> double_down_write_data_sem(orig_inode, donor_inode);
> /* Check the filesystem environment whether move_extent can be done */
> @@ -1412,6 +1415,8 @@ out:
> kfree(holecheck_path);
> }
> double_up_write_data_sem(orig_inode, donor_inode);
> + ext4_clear_inode_state(orig_inode, EXT4_STATE_DIOREAD_LOCK);
> + ext4_clear_inode_state(donor_inode, EXT4_STATE_DIOREAD_LOCK);
> ret2 = mext_inode_double_unlock(orig_inode, donor_inode);
>
> if (ret1)
> --
> 1.7.7.6
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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