Re: [PATCH v4 02/12] ext4: add a new helper to check if es must be kept

Jan Kara
2023-05-03T12:57:25Z

On Mon 24-04-23 11:38:36, Baokun Li wrote:
> In the extent status tree, we have extents which we can just drop without
> issues and extents we must not drop - this depends on the extent's status
> - currently ext4_es_is_delayed() extents must stay, others may be dropped.
>
> A helper function is added to help determine if the current extent can
> be dropped, although only ext4_es_is_delayed() extents cannot be dropped
> currently.
>
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Baokun Li <libaokun1@huawei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/ext4/extents_status.c | 34 +++++++++++++++++++++-------------
> 1 file changed, 21 insertions(+), 13 deletions(-)
>
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 7bc221038c6c..573723b23d19 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -448,6 +448,19 @@ static void ext4_es_list_del(struct inode *inode)
> spin_unlock(&sbi->s_es_lock);
> }
>
> +/*
> + * Returns true if we cannot fail to allocate memory for this extent_status
> + * entry and cannot reclaim it until its status changes.
> + */
> +static inline bool ext4_es_must_keep(struct extent_status *es)
> +{
> + /* fiemap, bigalloc, and seek_data/hole need to use it. */
> + if (ext4_es_is_delayed(es))
> + return true;
> +
> + return false;
> +}
> +
> static struct extent_status *
> ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
> ext4_fsblk_t pblk)
> @@ -460,10 +473,8 @@ ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
> es->es_len = len;
> es->es_pblk = pblk;
>
> - /*
> - * We don't count delayed extent because we never try to reclaim them
> - */
> - if (!ext4_es_is_delayed(es)) {
> + /* We never try to reclaim a must kept extent, so we don't count it. */
> + if (!ext4_es_must_keep(es)) {
> if (!EXT4_I(inode)->i_es_shk_nr++)
> ext4_es_list_add(inode);
> percpu_counter_inc(&EXT4_SB(inode->i_sb)->
> @@ -481,8 +492,8 @@ static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
> EXT4_I(inode)->i_es_all_nr--;
> percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);
>
> - /* Decrease the shrink counter when this es is not delayed */
> - if (!ext4_es_is_delayed(es)) {
> + /* Decrease the shrink counter when we can reclaim the extent. */
> + if (!ext4_es_must_keep(es)) {
> BUG_ON(EXT4_I(inode)->i_es_shk_nr == 0);
> if (!--EXT4_I(inode)->i_es_shk_nr)
> ext4_es_list_del(inode);
> @@ -853,7 +864,7 @@ int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
> if (err == -ENOMEM && __es_shrink(EXT4_SB(inode->i_sb),
> 128, EXT4_I(inode)))
> goto retry;
> - if (err == -ENOMEM && !ext4_es_is_delayed(&newes))
> + if (err == -ENOMEM && !ext4_es_must_keep(&newes))
> err = 0;
>
> if (sbi->s_cluster_ratio > 1 && test_opt(inode->i_sb, DELALLOC) &&
> @@ -1706,11 +1717,8 @@ static int es_do_reclaim_extents(struct ext4_inode_info *ei, ext4_lblk_t end,
>
> (*nr_to_scan)--;
> node = rb_next(&es->rb_node);
> - /*
> - * We can't reclaim delayed extent from status tree because
> - * fiemap, bigallic, and seek_data/hole need to use it.
> - */
> - if (ext4_es_is_delayed(es))
> +
> + if (ext4_es_must_keep(es))
> goto next;
> if (ext4_es_is_referenced(es)) {
> ext4_es_clear_referenced(es);
> @@ -1774,7 +1782,7 @@ void ext4_clear_inode_es(struct inode *inode)
> while (node) {
> es = rb_entry(node, struct extent_status, rb_node);
> node = rb_next(node);
> - if (!ext4_es_is_delayed(es)) {
> + if (!ext4_es_must_keep(es)) {
> rb_erase(&es->rb_node, &tree->root);
> ext4_es_free_extent(inode, es);
> }
> --
> 2.31.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR