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From:   Li Dongyang <dongyangli@ddn.com>
To:     linux-ext4@vger.kernel.org
Cc:     adilger@dilger.ca, sihara@ddn.com, wangshilong1991@gmail.com
Subject: [PATCH 1/2] ext4: introduce EXT4_BG_TRIMMED to optimize fstrim
Date:   Fri, 11 Aug 2023 16:19:04 +1000
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Currently the flag indicating block group has done fstrim is not
persistent, and trim status will be lost after remount, as
a result fstrim can not skip the already trimmed groups, which
could be slow on very large devices.

This patch introduces a new block group flag EXT4_BG_TRIMMED,
we need 1 extra block group descriptor write after trimming each
block group.
When clearing the flag, the block group descriptor is journalled
already so no extra overhead.

Add a new super block flag EXT2_FLAGS_TRACK_TRIM, to indicate if
we should honour EXT4_BG_TRIMMED when doing fstrim.
The new super block flag can be turned on/off via tune2fs.

Cc: Shuichi Ihara <sihara@ddn.com>
Cc: Andreas Dilger <adilger@dilger.ca>
Cc: Wang Shilong <wangshilong1991@gmail.com>
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
---
 fs/ext4/ext4.h      | 10 ++------
 fs/ext4/ext4_jbd2.h |  3 ++-
 fs/ext4/mballoc.c   | 62 +++++++++++++++++++++++++++++++++++----------
 3 files changed, 52 insertions(+), 23 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 0a2d55faa095..a990fb49b24f 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -437,6 +437,7 @@ struct flex_groups {
 #define EXT4_BG_INODE_UNINIT	0x0001 /* Inode table/bitmap not in use */
 #define EXT4_BG_BLOCK_UNINIT	0x0002 /* Block bitmap not in use */
 #define EXT4_BG_INODE_ZEROED	0x0004 /* On-disk itable initialized to zero */
+#define EXT4_BG_TRIMMED		0x0008 /* block group was trimmed */
 
 /*
  * Macro-instructions used to manage group descriptors
@@ -1166,6 +1167,7 @@ struct ext4_inode_info {
 #define EXT2_FLAGS_SIGNED_HASH		0x0001  /* Signed dirhash in use */
 #define EXT2_FLAGS_UNSIGNED_HASH	0x0002  /* Unsigned dirhash in use */
 #define EXT2_FLAGS_TEST_FILESYS		0x0004	/* to test development code */
+#define EXT2_FLAGS_TRACK_TRIM		0x0008  /* Track trim status in each bg */
 
 /*
  * Mount flags set via mount options or defaults
@@ -3412,7 +3414,6 @@ struct ext4_group_info {
 };
 
 #define EXT4_GROUP_INFO_NEED_INIT_BIT		0
-#define EXT4_GROUP_INFO_WAS_TRIMMED_BIT		1
 #define EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT	2
 #define EXT4_GROUP_INFO_IBITMAP_CORRUPT_BIT	3
 #define EXT4_GROUP_INFO_BBITMAP_CORRUPT		\
@@ -3427,13 +3428,6 @@ struct ext4_group_info {
 	(test_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT, &((grp)->bb_state)))
 #define EXT4_MB_GRP_IBITMAP_CORRUPT(grp)	\
 	(test_bit(EXT4_GROUP_INFO_IBITMAP_CORRUPT_BIT, &((grp)->bb_state)))
-
-#define EXT4_MB_GRP_WAS_TRIMMED(grp)	\
-	(test_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT, &((grp)->bb_state)))
-#define EXT4_MB_GRP_SET_TRIMMED(grp)	\
-	(set_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT, &((grp)->bb_state)))
-#define EXT4_MB_GRP_CLEAR_TRIMMED(grp)	\
-	(clear_bit(EXT4_GROUP_INFO_WAS_TRIMMED_BIT, &((grp)->bb_state)))
 #define EXT4_MB_GRP_TEST_AND_SET_READ(grp)	\
 	(test_and_set_bit(EXT4_GROUP_INFO_BBITMAP_READ_BIT, &((grp)->bb_state)))
 
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index 0c77697d5e90..ce529a454b2a 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -120,7 +120,8 @@
 #define EXT4_HT_MOVE_EXTENTS     9
 #define EXT4_HT_XATTR           10
 #define EXT4_HT_EXT_CONVERT     11
-#define EXT4_HT_MAX             12
+#define EXT4_HT_FS_TRIM		12
+#define EXT4_HT_MAX             13
 
 /**
  *   struct ext4_journal_cb_entry - Base structure for callback information.
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 21b903fe546e..80283be01363 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3849,15 +3849,6 @@ static void ext4_free_data_in_buddy(struct super_block *sb,
 	rb_erase(&entry->efd_node, &(db->bb_free_root));
 	mb_free_blocks(NULL, &e4b, entry->efd_start_cluster, entry->efd_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))
-		EXT4_MB_GRP_CLEAR_TRIMMED(db);
-
 	if (!db->bb_free_root.rb_node) {
 		/* No more items in the per group rb tree
 		 * balance refcounts from ext4_mb_free_metadata()
@@ -6587,8 +6578,7 @@ static void ext4_mb_clear_bb(handle_t *handle, struct inode *inode,
 					 " group:%u block:%d count:%lu failed"
 					 " with %d", block_group, bit, count,
 					 err);
-		} else
-			EXT4_MB_GRP_CLEAR_TRIMMED(e4b.bd_info);
+		}
 
 		ext4_lock_group(sb, block_group);
 		mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
@@ -6598,6 +6588,14 @@ static void ext4_mb_clear_bb(handle_t *handle, struct inode *inode,
 	ret = ext4_free_group_clusters(sb, gdp) + count_clusters;
 	ext4_free_group_clusters_set(sb, gdp, ret);
 	ext4_block_bitmap_csum_set(sb, gdp, bitmap_bh);
+	/*
+	 * 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))
+		gdp->bg_flags &= cpu_to_le16(~EXT4_BG_TRIMMED);
 	ext4_group_desc_csum_set(sb, block_group, gdp);
 	ext4_unlock_group(sb, block_group);
 
@@ -6995,10 +6993,19 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 		   ext4_grpblk_t minblocks, bool set_trimmed)
 {
 	struct ext4_buddy e4b;
+	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+	struct ext4_group_desc *gdp;
+	struct buffer_head *gd_bh;
 	int ret;
 
 	trace_ext4_trim_all_free(sb, group, start, max);
 
+	gdp = ext4_get_group_desc(sb, group, &gd_bh);
+	if (!gdp) {
+		ret = -EIO;
+		return ret;
+	}
+
 	ret = ext4_mb_load_buddy(sb, group, &e4b);
 	if (ret) {
 		ext4_warning(sb, "Error %d loading buddy information for %u",
@@ -7008,11 +7015,10 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 
 	ext4_lock_group(sb, group);
 
-	if (!EXT4_MB_GRP_WAS_TRIMMED(e4b.bd_info) ||
+	if (!(es->s_flags & cpu_to_le16(EXT2_FLAGS_TRACK_TRIM) &&
+	      gdp->bg_flags & cpu_to_le16(EXT4_BG_TRIMMED)) ||
 	    minblocks < EXT4_SB(sb)->s_last_trim_minblks) {
 		ret = ext4_try_to_trim_range(sb, &e4b, start, max, minblocks);
-		if (ret >= 0 && set_trimmed)
-			EXT4_MB_GRP_SET_TRIMMED(e4b.bd_info);
 	} else {
 		ret = 0;
 	}
@@ -7020,6 +7026,34 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 	ext4_unlock_group(sb, group);
 	ext4_mb_unload_buddy(&e4b);
 
+	if (ret > 0 && set_trimmed) {
+		int err;
+		handle_t *handle;
+
+		handle = ext4_journal_start_sb(sb, EXT4_HT_FS_TRIM, 1);
+		if (IS_ERR(handle)) {
+			ret = PTR_ERR(handle);
+			goto out_return;
+		}
+		err = ext4_journal_get_write_access(handle, sb, gd_bh,
+						    EXT4_JTR_NONE);
+		if (err) {
+			ret = err;
+			goto out_journal;
+		}
+		ext4_lock_group(sb, group);
+		gdp->bg_flags |= cpu_to_le16(EXT4_BG_TRIMMED);
+		ext4_group_desc_csum_set(sb, group, gdp);
+		ext4_unlock_group(sb, group);
+		err = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
+		if (err)
+			ret = err;
+out_journal:
+		err = ext4_journal_stop(handle);
+		if (err)
+			ret = err;
+	}
+out_return:
 	ext4_debug("trimmed %d blocks in the group %d\n",
 		ret, group);
 
-- 
2.41.0