[PATCH 4/4] ext4: Speed up FITRIM by recording flags in ext4_group_info.

[Tao Ma <tm@tao.ma>]

From: Tao Ma <boyu.mt@taobao.com>

In ext4, when FITRIM is called every time, we iterate all the
groups and do trim one by one. It is a bit time wasting if the
group has been trimmed and there is no change since the last
trim.

So this patch adds a new flag in ext4_group_info->bb_state to
indicate that the group has been trimmed, and it will be cleared
if some blocks is freed(in release_blocks_on_commit). Another
trim_minlen is added in ext4_sb_info to record the last minlen
we use to trim the volume, so that if the caller provide a small
one, we will go on the trim regardless of the bb_state. The idea
is inspired by Andreas  and Lukas Czerner.

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
---
 fs/ext4/ext4.h    |    8 +++++++-
 fs/ext4/mballoc.c |   22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0c8d97b..684f48e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1200,6 +1200,9 @@ struct ext4_sb_info {
 	struct ext4_li_request *s_li_request;
 	/* Wait multiplier for lazy initialization thread */
 	unsigned int s_li_wait_mult;
+
+	/* record the last minlen when FITRIM is called. */
+	u64 trim_minlen;
 };
 
 static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
@@ -1970,10 +1973,13 @@ struct ext4_group_info {
 					 * 5 free 8-block regions. */
 };
 
-#define EXT4_GROUP_INFO_NEED_INIT_BIT	0
+#define EXT4_GROUP_INFO_NEED_INIT_BIT		0
+#define EXT4_GROUP_INFO_HAS_BEEN_TRIMMED	1
 
 #define EXT4_MB_GRP_NEED_INIT(grp)	\
 	(test_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &((grp)->bb_state)))
+#define EXT4_MB_GRP_HAS_BEEN_TRIMMED(grp)	\
+	(test_bit(EXT4_GROUP_INFO_HAS_BEEN_TRIMMED, &((grp)->bb_state)))
 
 #define EXT4_MAX_CONTENTION		8
 #define EXT4_CONTENTION_THRESHOLD	2
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4eadac8..3f6b809 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1563,6 +1563,9 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
 	mb_set_bits(EXT4_MB_BITMAP(e4b), ex->fe_start, len0);
 	mb_check_buddy(e4b);
 
+	if (!ret)
+		EXT4_SB(sb)->trim_minlen = minlen;
+
 	return ret;
 }
 
@@ -2687,6 +2690,16 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
 		rb_erase(&entry->node, &(db->bb_free_root));
 		mb_free_blocks(NULL, &e4b, entry->start_blk, entry->count);
 
+		/*
+		 * Clear the trimmed flag for the group so that the next
+		 * ext4_trim_fs can trim it.
+		 * If the volume is mounted with -o discard, online discard
+		 * is supported and the free blocks will be trimmed online.
+		 */
+		if (!test_opt(sb, DISCARD))
+			clear_bit(EXT4_GROUP_INFO_HAS_BEEN_TRIMMED,
+				  &(db->bb_state));
+
 		if (!db->bb_free_root.rb_node) {
 			/* No more items in the per group rb tree
 			 * balance refcounts from ext4_mb_free_metadata()
@@ -4772,6 +4785,10 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
 
 	ext4_lock_group(sb, group);
 
+	if (EXT4_MB_GRP_HAS_BEEN_TRIMMED(e4b->bd_info) &&
+	    minblocks >= EXT4_SB(sb)->trim_minlen)
+		goto out;
+
 	trace_ext4_trim_all_free(sb, group, start, max);
 
 	while (start < max) {
@@ -4804,6 +4821,11 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b,
 		if ((e4b->bd_info->bb_free - free_count) < minblocks)
 			break;
 	}
+
+	if (!ret)
+		set_bit(EXT4_GROUP_INFO_HAS_BEEN_TRIMMED,
+			&(e4b->bd_info->bb_state));
+out:
 	ext4_unlock_group(sb, group);
 
 	ext4_debug("trimmed %d blocks in the group %d\n",
-- 
1.6.3.GIT