On Fri 28-09-12 19:44:06, 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.
Looks good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
>
> Changes from V2:
> - fix mistype in condition
> 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 | 14 ++++++++++++++
> fs/ext4/inode.c | 5 +++++
> fs/ext4/move_extent.c | 8 ++++++++
> 4 files changed, 44 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 9c3d004..885dc79 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1363,6 +1363,8 @@ 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) \
> @@ -2471,6 +2473,21 @@ 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 ebc7d83..9e6cdb6 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -811,11 +811,25 @@ retry:
> if (unlikely(!list_empty(&ei->i_completed_io_list)))
> ext4_flush_completed_IO(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))) {
> + inode_dio_done(inode);
> + goto locked;
> + }
> 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 {
> +locked:
> 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 1ea34e5..da52855 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4692,6 +4692,10 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
> return err;
> }
>
> + /* Wait for all existing dio workers */
> + ext4_inode_block_unlocked_dio(inode);
> + inode_dio_wait(inode);
> +
> jbd2_journal_lock_updates(journal);
>
> /*
> @@ -4711,6 +4715,7 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
> ext4_set_aops(inode);
>
> jbd2_journal_unlock_updates(journal);
> + ext4_inode_resume_unlocked_dio(inode);
>
> /* Finally we can mark the inode as dirty. */
>
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index c2e47da..0aaaf12 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -1325,6 +1325,12 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
> /* Protect orig and donor inodes against a truncate */
> mext_inode_double_lock(orig_inode, donor_inode);
>
> + /* Wait for all existing dio workers */
> + ext4_inode_block_unlocked_dio(orig_inode);
> + ext4_inode_block_unlocked_dio(donor_inode);
> + inode_dio_wait(orig_inode);
> + inode_dio_wait(donor_inode);
> +
> /* 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 */
> @@ -1523,6 +1529,8 @@ out:
> kfree(holecheck_path);
> }
> double_up_write_data_sem(orig_inode, donor_inode);
> + ext4_inode_resume_unlocked_dio(orig_inode);
> + ext4_inode_resume_unlocked_dio(donor_inode);
> mext_inode_double_unlock(orig_inode, donor_inode);
>
> return ret;
> --
> 1.7.7.6
>
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