On Fri, 15 Jan 2010 14:30:11 -0500, "Theodore Ts'o" <tytso@xxxxxxx> wrote:
> Allocate uninitialized extent before ext4 buffer write and
> convert the extent to initialized after io completes.
> The purpose is to make sure an extent can only be marked
> initialized after it has been written with new data so
> we can safely drop the i_mutex lock in ext4 DIO read without
> exposing stale data. This helps to improve multi-thread DIO
> read performance on high-speed disks.
>
> Skip the nobh and data=journal mount cases to make things simple for now.
>
> Signed-off-by: Jiaying Zhang <jiayingz@xxxxxxxxxx>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> fs/ext4/ext4.h | 12 +++++-
> fs/ext4/ext4_jbd2.h | 24 ++++++++++++
> fs/ext4/extents.c | 22 ++++++-----
> fs/ext4/inode.c | 105 ++++++++++++++++++++++++++++++++++++++++----------
> fs/ext4/super.c | 30 +++++++++++++--
> 5 files changed, 157 insertions(+), 36 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index b1dcbb7..b8b4887 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -134,6 +134,7 @@ struct mpage_da_data {
> int retval;
> };
> #define EXT4_IO_UNWRITTEN 0x1
> +#define EXT4_IO_WRITTEN 0x2
> typedef struct ext4_io_end {
> struct list_head list; /* per-file finished AIO list */
> struct inode *inode; /* file being written to */
> @@ -370,7 +371,7 @@ struct ext4_new_group_data {
> EXT4_GET_BLOCKS_CREATE_UNINIT_EXT)
> /* Convert extent to initialized after IO complete */
> #define EXT4_GET_BLOCKS_IO_CONVERT_EXT (EXT4_GET_BLOCKS_CONVERT|\
> - EXT4_GET_BLOCKS_IO_CREATE_EXT)
> + EXT4_GET_BLOCKS_CREATE_UNINIT_EXT)
>
> /*
> * Flags used by ext4_free_blocks
> @@ -761,6 +762,7 @@ struct ext4_inode_info {
> #define EXT4_MOUNT_QUOTA 0x80000 /* Some quota option set */
> #define EXT4_MOUNT_USRQUOTA 0x100000 /* "old" user quota */
> #define EXT4_MOUNT_GRPQUOTA 0x200000 /* "old" group quota */
> +#define EXT4_MOUNT_DIOREAD_NOLOCK 0x400000 /* Enable support for dio read nolocking */
> #define EXT4_MOUNT_JOURNAL_CHECKSUM 0x800000 /* Journal checksums */
> #define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT 0x1000000 /* Journal Async Commit */
> #define EXT4_MOUNT_I_VERSION 0x2000000 /* i_version support */
> @@ -1774,6 +1776,14 @@ static inline void set_bitmap_uptodate(struct buffer_head *bh)
> set_bit(BH_BITMAP_UPTODATE, &(bh)->b_state);
> }
>
> +/* BH_Uninit flag: blocks are allocated but uninitialized on disk */
> +enum ext4_state_bits {
> + BH_Uninit /* blocks are allocated but uninitialized on disk */
> + = BH_JBDPrivateStart,
> +};
> +
> +BUFFER_FNS(Uninit, uninit)
> +
I asked this in the last post. Why we need a new buffer head flag ?
Why can't we use the unwritten flag ?
-aneesh
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