f2fs: fix to avoid redundant discard during fstrim
Chao Yu
maintainerPATCH 1/1 f2fs: fix to avoid redundant discard during fstrim
From: Chao Yu <[email protected]>
With below test steps, f2fs will issue redundant discard when doing fstrim, the reason is that we issue discards for both prefree segments and consecutive freed region user wants to trim, part regions they covered are overlapped, here, we change to do not to issue any discard for prefree segments no matter in trimmed range or not.
1. mount -t f2fs -o discard /dev/zram0 /mnt/f2fs
2. fstrim -o 0 -l 3221225472 -m 2097152 -v /mnt/f2fs/
3. dd if=/dev/zero of=/mnt/f2fs/a bs=2M count=1
4. dd if=/dev/zero of=/mnt/f2fs/b bs=1M count=1
5. sync
6. rm /mnt/f2fs/a /mnt/f2fs/b
7. fstrim -o 0 -l 3221225472 -m 2097152 -v /mnt/f2fs/
Before:
<...>-5428 [001] ...1 9511.052125: f2fs_issue_discard: dev = (251,0), blkstart = 0x2200, blklen = 0x200 <...>-5428 [001] ...1 9511.052787: f2fs_issue_discard: dev = (251,0), blkstart = 0x2200, blklen = 0x300
After:
<...>-6764 [000] ...1 9720.382504: f2fs_issue_discard: dev = (251,0), blkstart = 0x2200, blklen = 0x300
--- fs/f2fs/segment.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)
fs/f2fs/segment.c +16 -4
@@ -710,21 +710,33 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi, struct cp_control *cpc)unsigned long *prefree_map = dirty_i->dirty_segmap[PRE ];unsigned int start =0 , end =-1 ;unsigned int secno, start_segno; +unsigned int trim_start = cpc->trim_start; +unsigned int trim_end = cpc->trim_end; +bool force = (cpc->reason ==CP_DISCARD );mutex_lock (&dirty_i->seglist_lock);while (1 ) {int i; +unsigned int trimmed =0 ; + start =find_next_bit (prefree_map,MAIN_SEGS (sbi), end +1 );if (start >=MAIN_SEGS (sbi))break ; end =find_next_zero_bit (prefree_map,MAIN_SEGS (sbi), start +1 ); -for (i = start; i < end; i++) -clear_bit (i, prefree_map); +for (i = start; i < end; i++) { +if (!force || (i >= trim_start && i <= trim_end)) { +clear_bit (i, prefree_map); + trimmed++; + } + } + + dirty_i->nr_dirty[PRE ] -= trimmed; - dirty_i->nr_dirty[PRE ] -= end - start; +if (force) +continue ;if (!test_opt (sbi,DISCARD ))continue ;
@@ -750,7 +762,7 @@ next:/* send small discards */ list_for_each_entry_safe (entry, this, head, list) { -if (cpc->reason ==CP_DISCARD && entry->len < cpc->trim_minlen) +if (force && entry->len < cpc->trim_minlen) goto skip;f2fs_issue_discard (sbi, entry->blkaddr, entry->len); cpc->trimmed += entry->len;
Signature · 1 line
2.7.2