On Fri 01-09-23 17:28:20, Fengnan Chang wrote:
> In commit a015434480dc("ext4: send parallel discards on commit
> completions"), issue all discard commands in parallel make all
> bios could merged into one request, so lowlevel drive can issue
> multi segments in one time which is more efficiency, but commit
> 55cdd0af2bc5 ("ext4: get discard out of jbd2 commit kthread contex")
> seems broke this way, let's fix it.
>
> In my test:
> 1. create 10 normal files, each file size is 10G.
> 2. deallocate file, punch a 16k holes every 32k.
> 3. trim all fs.
> the time of fstrim fs reduce from 6.7s to 1.3s.
>
> Signed-off-by: Fengnan Chang <changfengnan@xxxxxxxxxxxxx>
This seems to have fallen through the cracks... I'm sorry for that.
> static int ext4_try_to_trim_range(struct super_block *sb,
> struct ext4_buddy *e4b, ext4_grpblk_t start,
> ext4_grpblk_t max, ext4_grpblk_t minblocks)
> __acquires(ext4_group_lock_ptr(sb, e4b->bd_group))
> __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> {
> - ext4_grpblk_t next, count, free_count;
> + ext4_grpblk_t next, count, free_count, bak;
> void *bitmap;
> + struct ext4_free_data *entry = NULL, *fd, *nfd;
> + struct list_head discard_data_list;
> + struct bio *discard_bio = NULL;
> + struct blk_plug plug;
> + ext4_group_t group = e4b->bd_group;
> + struct ext4_free_extent ex;
> + bool noalloc = false;
> + int ret = 0;
> +
> + INIT_LIST_HEAD(&discard_data_list);
>
> bitmap = e4b->bd_bitmap;
> start = max(e4b->bd_info->bb_first_free, start);
> count = 0;
> free_count = 0;
>
> + blk_start_plug(&plug);
> while (start <= max) {
> start = mb_find_next_zero_bit(bitmap, max + 1, start);
> if (start > max)
> break;
> + bak = start;
> next = mb_find_next_bit(bitmap, max + 1, start);
> -
> if ((next - start) >= minblocks) {
> - int ret = ext4_trim_extent(sb, start, next - start, e4b);
> + /* when only one segment, there is no need to alloc entry */
> + noalloc = (free_count == 0) && (next >= max);
Is the single extent case really worth the complications to save one
allocation? I don't think it is but maybe I'm missing something. Otherwise
the patch looks good to me!
Honza
>
> - if (ret && ret != -EOPNOTSUPP)
> + trace_ext4_trim_extent(sb, group, start, next - start);
> + ex.fe_start = start;
> + ex.fe_group = group;
> + ex.fe_len = next - start;
> + /*
> + * Mark blocks used, so no one can reuse them while
> + * being trimmed.
> + */
> + mb_mark_used(e4b, &ex);
> + ext4_unlock_group(sb, group);
> + ret = ext4_issue_discard(sb, group, start, next - start, &discard_bio);
> + if (!noalloc) {
> + entry = kmem_cache_alloc(ext4_free_data_cachep,
> + GFP_NOFS|__GFP_NOFAIL);
> + entry->efd_start_cluster = start;
> + entry->efd_count = next - start;
> + list_add_tail(&entry->efd_list, &discard_data_list);
> + }
> + ext4_lock_group(sb, group);
> + if (ret < 0)
> break;
> count += next - start;
> }
> @@ -6959,6 +6950,22 @@ __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> break;
> }
>
> + if (discard_bio) {
> + ext4_unlock_group(sb, e4b->bd_group);
> + submit_bio_wait(discard_bio);
> + bio_put(discard_bio);
> + ext4_lock_group(sb, e4b->bd_group);
> + }
> + blk_finish_plug(&plug);
> +
> + if (noalloc && free_count)
> + mb_free_blocks(NULL, e4b, bak, free_count);
> +
> + list_for_each_entry_safe(fd, nfd, &discard_data_list, efd_list) {
> + mb_free_blocks(NULL, e4b, fd->efd_start_cluster, fd->efd_count);
> + kmem_cache_free(ext4_free_data_cachep, fd);
> + }
> +
> return count;
> }
>
> --
> 2.20.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
