On Mon 24-09-12 15:44:15, 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.
>
> Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> ---
> fs/ext4/ext4.h | 17 +++++++++++++++++
> fs/ext4/indirect.c | 13 +++++++++++++
> fs/ext4/inode.c | 5 +++++
> fs/ext4/move_extent.c | 8 ++++++++
> 4 files changed, 43 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index cc423cf..fccd263 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1350,6 +1350,8 @@ 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) \
> @@ -2462,6 +2464,21 @@ static inline void set_bitmap_uptodate(struct buffer_head *bh)
> set_bit(BH_BITMAP_UPTODATE, &(bh)->b_state);
> }
>
> +/*
> + * Disable DIO read nolock optimization, so new dioreaders will be forced
> + * to grab i_mutex
> + */
> +static inline void ext4_inode_block_unlocked_dio(struct inode *inode)
> +{
> + ext4_set_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> + smp_mb();
> +}
> +static inline void ext4_inode_resume_unlocked_dio(struct inode *inode)
> +{
> + smp_mb();
> + ext4_clear_inode_state(inode, EXT4_STATE_DIOREAD_LOCK);
> +}
> +
> #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
>
> /* For ioend & aio unwritten conversion wait queues */
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 251e35f..ec38f81 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -810,10 +810,23 @@ retry:
> if (unlikely(!list_empty(&ei->i_completed_io_list)))
> ext4_unwritten_wait(inode);
>
> + /*
> + * Nolock dioread optimization may be dynamically disabled
> + * via ext4_inode_block_unlocked_dio(). 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))) {
Isn't this condition reverted? We want to retry if
EXT4_STATE_DIOREAD_LOCK is set, don't we?
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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