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Date: Tue, 4 Dec 2018 18:55:11 +0800
From: Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>
To: linux-ext4@...r.kernel.org
Cc: jack@...e.cz, ted <tytso@....edu>
Subject: Re: [PATCH 1/2] ext4: try to merge unwritten extents who are also not
under io
hi,
ping :)
Regards,
Xiaoguang Wang
> Currently in ext4_can_extents_be_merged(), if one file has unwritten
> extents under io, we will not merge any other unwritten extents, even
> they are not in range of those unwritten extents under io. This limit
> is coarse, indeed we can merge these unwritten extents that are not
> under io.
>
> Here add a new ES_IO_B flag to track unwritten extents under io in
> extents status tree. When we try to merge unwritten extents, search
> given extents in extents status tree, if not found, then we can merge
> these unwritten extents.
>
> Note currently we only track unwritten extents under io.
>
> Signed-off-by: Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>
> ---
> fs/ext4/extents.c | 29 ++++++++++++++++++++++++++++-
> fs/ext4/extents_status.c | 9 +++++++++
> fs/ext4/extents_status.h | 10 +++++++++-
> fs/ext4/inode.c | 10 ++++++++++
> 4 files changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 240b6dea5441..a93378cd1152 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1713,6 +1713,33 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
> return err;
> }
>
> +static int ext4_unwritten_extent_under_io(struct inode *inode,
> + struct ext4_extent *ex1, struct ext4_extent *ex2)
> +{
> + unsigned short len;
> +
> + /*
> + * The check for IO to unwritten extent is somewhat racy as we
> + * increment i_unwritten / set EXT4_STATE_DIO_UNWRITTEN only after
> + * dropping i_data_sem. But reserved blocks should save us in that
> + * case.
> + */
> + if (atomic_read(&EXT4_I(inode)->i_unwritten) == 0)
> + return 0;
> +
> + len = ext4_ext_get_actual_len(ex1);
> + if (ext4_es_scan_range(inode, &ext4_es_is_under_io, ex1->ee_block,
> + ex1->ee_block + len - 1))
> + return 1;
> +
> + len = ext4_ext_get_actual_len(ex2);
> + if (ext4_es_scan_range(inode, &ext4_es_is_under_io, ex2->ee_block,
> + ex2->ee_block + len - 1))
> + return 1;
> +
> + return 0;
> +}
> +
> int
> ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
> struct ext4_extent *ex2)
> @@ -1744,7 +1771,7 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
> */
> if (ext4_ext_is_unwritten(ex1) &&
> (ext4_test_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN) ||
> - atomic_read(&EXT4_I(inode)->i_unwritten) ||
> + ext4_unwritten_extent_under_io(inode, ex1, ex2) ||
> (ext1_ee_len + ext2_ee_len > EXT_UNWRITTEN_MAX_LEN)))
> return 0;
> #ifdef AGGRESSIVE_TEST
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 2b439afafe13..04bbd8b7f8f1 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -1332,6 +1332,15 @@ static int es_do_reclaim_extents(struct ext4_inode_info *ei, ext4_lblk_t end,
> */
> if (ext4_es_is_delayed(es))
> goto next;
> +
> + /*
> + * we don't reclaim unwritten extent under io because we use
> + * it to check whether we can merge other unwritten extents
> + * who are not under io, and when io completes, then we can
> + * reclaim this extent.
> + */
> + if (ext4_es_is_under_io(es))
> + goto next;
> if (ext4_es_is_referenced(es)) {
> ext4_es_clear_referenced(es);
> goto next;
> diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
> index 131a8b7df265..29a985600a47 100644
> --- a/fs/ext4/extents_status.h
> +++ b/fs/ext4/extents_status.h
> @@ -36,6 +36,7 @@ enum {
> ES_DELAYED_B,
> ES_HOLE_B,
> ES_REFERENCED_B,
> + ES_IO_B,
> ES_FLAGS
> };
>
> @@ -47,11 +48,13 @@ enum {
> #define EXTENT_STATUS_DELAYED (1 << ES_DELAYED_B)
> #define EXTENT_STATUS_HOLE (1 << ES_HOLE_B)
> #define EXTENT_STATUS_REFERENCED (1 << ES_REFERENCED_B)
> +#define EXTENT_STATUS_IO (1 << ES_IO_B)
>
> #define ES_TYPE_MASK ((ext4_fsblk_t)(EXTENT_STATUS_WRITTEN | \
> EXTENT_STATUS_UNWRITTEN | \
> EXTENT_STATUS_DELAYED | \
> - EXTENT_STATUS_HOLE) << ES_SHIFT)
> + EXTENT_STATUS_HOLE | \
> + EXTENT_STATUS_IO) << ES_SHIFT)
>
> struct ext4_sb_info;
> struct ext4_extent;
> @@ -173,6 +176,11 @@ static inline int ext4_es_is_delayed(struct extent_status *es)
> return (ext4_es_type(es) & EXTENT_STATUS_DELAYED) != 0;
> }
>
> +static inline int ext4_es_is_under_io(struct extent_status *es)
> +{
> + return (ext4_es_type(es) & EXTENT_STATUS_IO) != 0;
> +}
> +
> static inline int ext4_es_is_hole(struct extent_status *es)
> {
> return (ext4_es_type(es) & EXTENT_STATUS_HOLE) != 0;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 22a9d8159720..516966197257 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -704,6 +704,16 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
> ext4_es_scan_range(inode, &ext4_es_is_delayed, map->m_lblk,
> map->m_lblk + map->m_len - 1))
> status |= EXTENT_STATUS_DELAYED;
> + /*
> + * track unwritten extent under io. when io completes, we'll
> + * convert unwritten extent to written, ext4_es_insert_extent()
> + * will be called again to insert this written extent, then
> + * EXTENT_STATUS_IO will be cleared automatically, see remove
> + * logic in ext4_es_insert_extent().
> + */
> + if ((status & EXTENT_STATUS_UNWRITTEN) && (flags &
> + EXT4_GET_BLOCKS_IO_SUBMIT))
> + status |= EXTENT_STATUS_IO;
> ret = ext4_es_insert_extent(inode, map->m_lblk, map->m_len,
> map->m_pblk, status);
> if (ret < 0) {
>
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