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Subject[PATCH 2/5] f2fs: add key functions for small discards
Date
This patch adds key functions to activate the small discard feature.

Note that this procedure is conducted during the checkpoint only.

In flush_sit_entries(), when a new dirty sit entry is flushed, f2fs calls
add_discard_addrs() which searches candidates to be discarded.
The candidates should be marked *invalidated* and also previous checkpoint
recognizes it as *valid*.

At the end of a checkpoint procedure, f2fs throws discards based on the
discard entry list.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
---
fs/f2fs/segment.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 823526e..505a889 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -266,6 +266,47 @@ static void locate_dirty_segment(struct f2fs_sb_info *sbi, unsigned int segno)
mutex_unlock(&dirty_i->seglist_lock);
}

+static void add_discard_addrs(struct f2fs_sb_info *sbi,
+ unsigned int segno, struct seg_entry *se)
+{
+ struct list_head *head = &SM_I(sbi)->discard_list;
+ struct discard_entry *new;
+ int entries = SIT_VBLOCK_MAP_SIZE / sizeof(unsigned long);
+ int max_blocks = sbi->blocks_per_seg;
+ unsigned long *cur_map = (unsigned long *)se->cur_valid_map;
+ unsigned long *ckpt_map = (unsigned long *)se->ckpt_valid_map;
+ unsigned long dmap[entries];
+ unsigned int start = 0, end = -1;
+ int i;
+
+ if (!test_opt(sbi, DISCARD))
+ return;
+
+ /* zero block will be discarded through the prefree list */
+ if (!se->valid_blocks || se->valid_blocks == max_blocks)
+ return;
+
+ /* SIT_VBLOCK_MAP_SIZE should be multiple of sizeof(unsigned long) */
+ for (i = 0; i < entries; i++)
+ dmap[i] = (cur_map[i] ^ ckpt_map[i]) & ckpt_map[i];
+
+ while (SM_I(sbi)->nr_discards <= SM_I(sbi)->max_discards) {
+ start = __find_rev_next_bit(dmap, max_blocks, end + 1);
+ if (start >= max_blocks)
+ break;
+
+ end = __find_rev_next_zero_bit(dmap, max_blocks, start + 1);
+
+ new = f2fs_kmem_cache_alloc(discard_entry_slab, GFP_NOFS);
+ INIT_LIST_HEAD(&new->list);
+ new->blkaddr = START_BLOCK(sbi, segno) + start;
+ new->len = end - start;
+
+ list_add_tail(&new->list, head);
+ SM_I(sbi)->nr_discards += end - start;
+ }
+}
+
/*
* Should call clear_prefree_segments after checkpoint is done.
*/
@@ -288,6 +329,9 @@ static void set_prefree_as_free_segments(struct f2fs_sb_info *sbi)

void clear_prefree_segments(struct f2fs_sb_info *sbi)
{
+ struct list_head *head = &(SM_I(sbi)->discard_list);
+ struct list_head *this, *next;
+ struct discard_entry *entry;
struct dirty_seglist_info *dirty_i = DIRTY_I(sbi);
unsigned long *prefree_map = dirty_i->dirty_segmap[PRE];
unsigned int total_segs = TOTAL_SEGS(sbi);
@@ -318,6 +362,18 @@ void clear_prefree_segments(struct f2fs_sb_info *sbi)
GFP_NOFS, 0);
}
mutex_unlock(&dirty_i->seglist_lock);
+
+ /* send small discards */
+ list_for_each_safe(this, next, head) {
+ entry = list_entry(this, struct discard_entry, list);
+ blkdev_issue_discard(sbi->sb->s_bdev,
+ entry->blkaddr << sbi->log_sectors_per_block,
+ (1 << sbi->log_sectors_per_block) * entry->len,
+ GFP_NOFS, 0);
+ list_del(&entry->list);
+ SM_I(sbi)->nr_discards -= entry->len;
+ kmem_cache_free(discard_entry_slab, entry);
+ }
}

static void __mark_sit_entry_dirty(struct f2fs_sb_info *sbi, unsigned int segno)
@@ -1469,6 +1525,10 @@ void flush_sit_entries(struct f2fs_sb_info *sbi)

sit_offset = SIT_ENTRY_OFFSET(sit_i, segno);

+ /* add discard candidates */
+ if (SM_I(sbi)->nr_discards < SM_I(sbi)->max_discards)
+ add_discard_addrs(sbi, segno, se);
+
if (flushed)
goto to_sit_page;

--
1.8.4.474.g128a96c


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