On Mon, Apr 08, 2013 at 11:32:29PM +0200, Jan Kara wrote:
> Since PageWriteback bit is now cleared after extents are converted from
> unwritten to written ones, we have full exclusion of writeback path from
> truncate (truncate_inode_pages() waits for PageWriteback bits to get cleared
> on all invalidated pages). Exclusion from DIO path is achieved by
> inode_dio_wait() call in ext4_setattr(). So there's no need to wait for
> extent convertion in ext4_ext_truncate() anymore.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
Regards,
- Zheng
> ---
> fs/ext4/extents.c | 6 ------
> fs/ext4/page-io.c | 9 ++++++++-
> 2 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index ae22735..ca4ff71 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4256,12 +4256,6 @@ void ext4_ext_truncate(struct inode *inode)
> int err = 0;
>
> /*
> - * finish any pending end_io work so we won't run the risk of
> - * converting any truncated blocks to initialized later
> - */
> - ext4_flush_unwritten_io(inode);
> -
> - /*
> * probably first extent we're gonna free will be last in block
> */
> err = ext4_writepage_trans_blocks(inode);
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 2967794..2f0b943 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -145,7 +145,14 @@ static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
> wake_up_all(ext4_ioend_wq(inode));
> }
>
> -/* check a range of space and convert unwritten extents to written. */
> +/*
> + * Check a range of space and convert unwritten extents to written. Note that
> + * we are protected from truncate touching same part of extent tree by the
> + * fact that truncate code waits for all DIO to finish (thus exclusion from
> + * direct IO is achieved) and also waits for PageWriteback bits. Thus we
> + * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
> + * completed (happens from ext4_free_ioend()).
> + */
> static int ext4_end_io(ext4_io_end_t *io)
> {
> struct inode *inode = io->inode;
> --
> 1.7.1
>
> --
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