Re: [RFC v3 3/8] ext4: Refactor code in ext4_mb_normalize_request() and ext4_mb_use_preallocated()

Jan Kara
2022-09-29T11:30:10Z

On Tue 27-09-22 14:46:43, Ojaswin Mujoo wrote:
> Change some variable names to be more consistent and
> refactor some of the code to make it easier to read.
>
> There are no functional changes in this patch
>
> Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

Looks good, although I have to say I don't find renaming pa -> tmp_pa
making the code any more readable. Anyways, feel free to add:

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

Honza

> ---
> fs/ext4/mballoc.c | 97 ++++++++++++++++++++++++-----------------------
> 1 file changed, 49 insertions(+), 48 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 8be6f8765a6f..84950df709bb 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4000,7 +4000,8 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
> loff_t orig_size __maybe_unused;
> ext4_lblk_t start;
> struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
> - struct ext4_prealloc_space *pa;
> + struct ext4_prealloc_space *tmp_pa;
> + ext4_lblk_t tmp_pa_start, tmp_pa_end;
>
> /* do normalize only data requests, metadata requests
> do not need preallocation */
> @@ -4103,56 +4104,53 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
>
> /* check we don't cross already preallocated blocks */
> rcu_read_lock();
> - list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
> - ext4_lblk_t pa_end;
> -
> - if (pa->pa_deleted)
> + list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {
> + if (tmp_pa->pa_deleted)
> continue;
> - spin_lock(&pa->pa_lock);
> - if (pa->pa_deleted) {
> - spin_unlock(&pa->pa_lock);
> + spin_lock(&tmp_pa->pa_lock);
> + if (tmp_pa->pa_deleted) {
> + spin_unlock(&tmp_pa->pa_lock);
> continue;
> }
>
> - pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
> - pa->pa_len);
> + tmp_pa_start = tmp_pa->pa_lstart;
> + tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);
>
> /* PA must not overlap original request */
> - BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
> - ac->ac_o_ex.fe_logical < pa->pa_lstart));
> + BUG_ON(!(ac->ac_o_ex.fe_logical >= tmp_pa_end ||
> + ac->ac_o_ex.fe_logical < tmp_pa_start));
>
> /* skip PAs this normalized request doesn't overlap with */
> - if (pa->pa_lstart >= end || pa_end <= start) {
> - spin_unlock(&pa->pa_lock);
> + if (tmp_pa_start >= end || tmp_pa_end <= start) {
> + spin_unlock(&tmp_pa->pa_lock);
> continue;
> }
> - BUG_ON(pa->pa_lstart <= start && pa_end >= end);
> + BUG_ON(tmp_pa_start <= start && tmp_pa_end >= end);
>
> /* adjust start or end to be adjacent to this pa */
> - if (pa_end <= ac->ac_o_ex.fe_logical) {
> - BUG_ON(pa_end < start);
> - start = pa_end;
> - } else if (pa->pa_lstart > ac->ac_o_ex.fe_logical) {
> - BUG_ON(pa->pa_lstart > end);
> - end = pa->pa_lstart;
> + if (tmp_pa_end <= ac->ac_o_ex.fe_logical) {
> + BUG_ON(tmp_pa_end < start);
> + start = tmp_pa_end;
> + } else if (tmp_pa_start > ac->ac_o_ex.fe_logical) {
> + BUG_ON(tmp_pa_start > end);
> + end = tmp_pa_start;
> }
> - spin_unlock(&pa->pa_lock);
> + spin_unlock(&tmp_pa->pa_lock);
> }
> rcu_read_unlock();
> size = end - start;
>
> /* XXX: extra loop to check we really don't overlap preallocations */
> rcu_read_lock();
> - list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
> - ext4_lblk_t pa_end;
> + list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {
> + spin_lock(&tmp_pa->pa_lock);
> + if (tmp_pa->pa_deleted == 0) {
> + tmp_pa_start = tmp_pa->pa_lstart;
> + tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);
>
> - spin_lock(&pa->pa_lock);
> - if (pa->pa_deleted == 0) {
> - pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
> - pa->pa_len);
> - BUG_ON(!(start >= pa_end || end <= pa->pa_lstart));
> + BUG_ON(!(start >= tmp_pa_end || end <= tmp_pa_start));
> }
> - spin_unlock(&pa->pa_lock);
> + spin_unlock(&tmp_pa->pa_lock);
> }
> rcu_read_unlock();
>
> @@ -4362,7 +4360,8 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
> int order, i;
> struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
> struct ext4_locality_group *lg;
> - struct ext4_prealloc_space *pa, *cpa = NULL;
> + struct ext4_prealloc_space *tmp_pa, *cpa = NULL;
> + ext4_lblk_t tmp_pa_start, tmp_pa_end;
> ext4_fsblk_t goal_block;
>
> /* only data can be preallocated */
> @@ -4371,18 +4370,20 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
>
> /* first, try per-file preallocation */
> rcu_read_lock();
> - list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
> + list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {
>
> /* all fields in this condition don't change,
> * so we can skip locking for them */
> - if (ac->ac_o_ex.fe_logical < pa->pa_lstart ||
> - ac->ac_o_ex.fe_logical >= (pa->pa_lstart +
> - EXT4_C2B(sbi, pa->pa_len)))
> + tmp_pa_start = tmp_pa->pa_lstart;
> + tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);
> +
> + if (ac->ac_o_ex.fe_logical < tmp_pa_start ||
> + ac->ac_o_ex.fe_logical >= tmp_pa_end)
> continue;
>
> /* non-extent files can't have physical blocks past 2^32 */
> if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)) &&
> - (pa->pa_pstart + EXT4_C2B(sbi, pa->pa_len) >
> + (tmp_pa->pa_pstart + EXT4_C2B(sbi, tmp_pa->pa_len) >
> EXT4_MAX_BLOCK_FILE_PHYS)) {
> /*
> * Since PAs don't overlap, we won't find any
> @@ -4392,16 +4393,16 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
> }
>
> /* found preallocated blocks, use them */
> - spin_lock(&pa->pa_lock);
> - if (pa->pa_deleted == 0 && pa->pa_free) {
> - atomic_inc(&pa->pa_count);
> - ext4_mb_use_inode_pa(ac, pa);
> - spin_unlock(&pa->pa_lock);
> + spin_lock(&tmp_pa->pa_lock);
> + if (tmp_pa->pa_deleted == 0 && tmp_pa->pa_free) {
> + atomic_inc(&tmp_pa->pa_count);
> + ext4_mb_use_inode_pa(ac, tmp_pa);
> + spin_unlock(&tmp_pa->pa_lock);
> ac->ac_criteria = 10;
> rcu_read_unlock();
> return true;
> }
> - spin_unlock(&pa->pa_lock);
> + spin_unlock(&tmp_pa->pa_lock);
> }
> rcu_read_unlock();
>
> @@ -4425,16 +4426,16 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
> */
> for (i = order; i < PREALLOC_TB_SIZE; i++) {
> rcu_read_lock();
> - list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[i],
> + list_for_each_entry_rcu(tmp_pa, &lg->lg_prealloc_list[i],
> pa_inode_list) {
> - spin_lock(&pa->pa_lock);
> - if (pa->pa_deleted == 0 &&
> - pa->pa_free >= ac->ac_o_ex.fe_len) {
> + spin_lock(&tmp_pa->pa_lock);
> + if (tmp_pa->pa_deleted == 0 &&
> + tmp_pa->pa_free >= ac->ac_o_ex.fe_len) {
>
> cpa = ext4_mb_check_group_pa(goal_block,
> - pa, cpa);
> + tmp_pa, cpa);
> }
> - spin_unlock(&pa->pa_lock);
> + spin_unlock(&tmp_pa->pa_lock);
> }
> rcu_read_unlock();
> }
> --
> 2.31.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR