This patch free blocks too earily when do discard, maybe cause data
corrupt, I'll fix this in
next version.
Fengnan Chang <changfengnan@xxxxxxxxxxxxx> 于2023年6月15日周四 19:12写道：
>
> 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, the time of fstrim fs with multi big sparse file
> reduce from 6.7s to 1.3s.
>
> Signed-off-by: Fengnan Chang <changfengnan@xxxxxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index a2475b8c9fb5..e5a27fd2e959 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -6790,7 +6790,7 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
> * be called with under the group lock.
> */
> static int ext4_trim_extent(struct super_block *sb,
> - int start, int count, struct ext4_buddy *e4b)
> + int start, int count, struct ext4_buddy *e4b, struct bio **biop)
> __releases(bitlock)
> __acquires(bitlock)
> {
> @@ -6812,7 +6812,7 @@ __acquires(bitlock)
> */
> mb_mark_used(e4b, &ex);
> ext4_unlock_group(sb, group);
> - ret = ext4_issue_discard(sb, group, start, count, NULL);
> + ret = ext4_issue_discard(sb, group, start, count, biop);
> ext4_lock_group(sb, group);
> mb_free_blocks(NULL, e4b, start, ex.fe_len);
> return ret;
> @@ -6826,12 +6826,15 @@ __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> {
> ext4_grpblk_t next, count, free_count;
> void *bitmap;
> + struct bio *discard_bio = NULL;
> + struct blk_plug plug;
>
> bitmap = e4b->bd_bitmap;
> start = (e4b->bd_info->bb_first_free > start) ?
> 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);
> @@ -6840,7 +6843,7 @@ __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> next = mb_find_next_bit(bitmap, max + 1, start);
>
> if ((next - start) >= minblocks) {
> - int ret = ext4_trim_extent(sb, start, next - start, e4b);
> + int ret = ext4_trim_extent(sb, start, next - start, e4b, &discard_bio);
>
> if (ret && ret != -EOPNOTSUPP)
> break;
> @@ -6864,6 +6867,14 @@ __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);
> +
> return count;
> }
>
> --
> 2.37.1 (Apple Git-137.1)
>
