Re: [PATCH 2/4 v2] avoid perform unwritten convertion for direct IO over non fallocated space

[Curt Wohlgemuth <curtw@google.com>]

Hi Mingming:

On Thu, Oct 8, 2009 at 6:13 PM, Mingming <cmm@us.ibm.com> wrote:
> ext4: avoid perform unwritten convertion for direct IO over non fallocated space
>
> When direct IO complete, without this patch, it always check and convert
> the range covered by the completed IO to be written. This is unnecessary
> if the range doesn't has any preallocated area or holes. This patch add
> a state flag to alart direct IO code to only run the convertion when
> there is unwritten extents being covered in this IO.
>
> Signed-off-by: Mingming Cao <cmm@us.ibm.com>
> ---
>  fs/ext4/ext4.h    |    1 +
>  fs/ext4/extents.c |   22 +++++++++++++++++-----
>  fs/ext4/inode.c   |    4 +++-
>  3 files changed, 21 insertions(+), 6 deletions(-)
>
> Index: linux-2.6.31-rc4/fs/ext4/ext4.h
> ===================================================================
> --- linux-2.6.31-rc4.orig/fs/ext4/ext4.h
> +++ linux-2.6.31-rc4/fs/ext4/ext4.h
> @@ -299,6 +299,7 @@ static inline __u32 ext4_mask_flags(umod
>  #define EXT4_STATE_XATTR               0x00000004 /* has in-inode xattrs */
>  #define EXT4_STATE_NO_EXPAND           0x00000008 /* No space for expansion */
>  #define EXT4_STATE_DA_ALLOC_CLOSE      0x00000010 /* Alloc DA blks on close */
> +#define EXT4_STATE_DIO_UNWRITTEN       0x00000020 /* need convert on dio done*/

You'll need to change this value, since EXT4_STATE_EXT_MIGRATE has
already been assigned 0x20.

Thanks,
Curt


>
>  /* Used to pass group descriptor data when online resize is done */
>  struct ext4_new_group_input {
> Index: linux-2.6.31-rc4/fs/ext4/extents.c
> ===================================================================
> --- linux-2.6.31-rc4.orig/fs/ext4/extents.c
> +++ linux-2.6.31-rc4/fs/ext4/extents.c
> @@ -3029,12 +3029,18 @@ ext4_ext_handle_uninitialized_extents(ha
>                ret = ext4_split_unwritten_extents(handle,
>                                                inode, path, iblock,
>                                                max_blocks, flags);
> -               /* flag the io_end struct that we need convert when IO done */
> +               /*
> +                * Flag the inode(non aio case) or end_io struct (aio case)
> +                * that this IO needs to convertion to written when IO is
> +                * completed
> +                */
>                if (io)
>                        io->flag = DIO_AIO_UNWRITTEN;
> +               else
> +                       EXT4_I(inode)->i_state |= EXT4_STATE_DIO_UNWRITTEN;
>                goto out;
>        }
> -       /* DIO end_io complete, convert the filled extent to written */
> +       /* async DIO end_io complete, convert the filled extent to written */
>        if (flags == EXT4_GET_BLOCKS_DIO_CONVERT_EXT) {
>                ret = ext4_convert_unwritten_extents_dio(handle, inode,
>                                                        path);
> @@ -3276,10 +3282,16 @@ int ext4_ext_get_blocks(handle_t *handle
>                 * To avoid unecessary convertion for every aio dio rewrite
>                 * to the mid of file, here we flag the IO that is really
>                 * need the convertion.
> -                *
> +                * For non asycn direct IO case, flag the inode state
> +                * that we need to perform convertion when IO is done.
>                 */
> -               if (io && flags == EXT4_GET_BLOCKS_DIO_CREATE_EXT)
> -                       io->flag = DIO_AIO_UNWRITTEN;
> +               if (flags == EXT4_GET_BLOCKS_DIO_CREATE_EXT) {
> +                       if (io)
> +                               io->flag = DIO_AIO_UNWRITTEN;
> +                       else
> +                               EXT4_I(inode)->i_state |=
> +                                       EXT4_STATE_DIO_UNWRITTEN;;
> +               }
>        }
>        err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
>        if (err) {
> Index: linux-2.6.31-rc4/fs/ext4/inode.c
> ===================================================================
> --- linux-2.6.31-rc4.orig/fs/ext4/inode.c
> +++ linux-2.6.31-rc4/fs/ext4/inode.c
> @@ -3693,7 +3693,8 @@ static ssize_t ext4_ext_direct_IO(int rw
>                if (ret != -EIOCBQUEUED && ret <= 0 && iocb->private) {
>                        ext4_free_io_end(iocb->private);
>                        iocb->private = NULL;
> -               } else if (ret > 0){
> +               } else if (ret > 0 && EXT4_I(inode)->i_state &
> +                               EXT4_STATE_DIO_UNWRITTEN){
>                        int err;
>                        /*
>                         * for non AIO case, since the IO is already
> @@ -3703,6 +3704,7 @@ static ssize_t ext4_ext_direct_IO(int rw
>                                                                offset, ret);
>                        if (err < 0)
>                                ret = err;
> +                       EXT4_I(inode)->i_state &= ~EXT4_STATE_DIO_UNWRITTEN;
>                }
>                return ret;
>        }
>
>
>
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