[PATCH v6 01/11] ext4: factor out codes to update block bitmap and group descriptor on disk from ext4_mb_mark_bb

[Kemeng Shi]

There are several reasons to add a general function to update block
bitmap and group descriptor on disk:
1. pair behavior of alloc/free bits. For example,
ext4_mb_new_blocks_simple will update free_clusters in struct flex_groups
in ext4_mb_mark_bb while ext4_free_blocks_simple forgets this.
2. remove repeat code to read from disk, update and write back to disk.
3. reduce future unit test mocks to catch real IO to update structure
on disk.

Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Reviewed-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>
---
 fs/ext4/mballoc.c | 169 +++++++++++++++++++++++++++-------------------
 1 file changed, 99 insertions(+), 70 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index c91db9f57524..e2be572deb75 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3952,6 +3952,100 @@ void ext4_exit_mballoc(void)
 	ext4_groupinfo_destroy_slabs();
 }
 
+/*
+ * Collect global setting to reduce the number of variable passing to
+ * ext4_mb_mark_context. Pass target group blocks range directly to
+ * reuse the prepared global setting for multiple block ranges and
+ * to show clearly the specific block range will be marked.
+ */
+struct ext4_mark_context {
+	struct super_block *sb;
+	int state;
+};
+
+static inline void ext4_mb_prepare_mark_context(struct ext4_mark_context *mc,
+						struct super_block *sb,
+						int state)
+{
+	mc->sb = sb;
+	mc->state = state;
+}
+
+static int
+ext4_mb_mark_context(struct ext4_mark_context *mc, ext4_group_t group,
+		     ext4_grpblk_t blkoff, ext4_grpblk_t len)
+{
+	struct super_block *sb = mc->sb;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct buffer_head *bitmap_bh = NULL;
+	struct ext4_group_desc *gdp;
+	struct buffer_head *gdp_bh;
+	int err;
+	unsigned int i, already, changed;
+
+	bitmap_bh = ext4_read_block_bitmap(sb, group);
+	if (IS_ERR(bitmap_bh))
+		return PTR_ERR(bitmap_bh);
+
+	err = -EIO;
+	gdp = ext4_get_group_desc(sb, group, &gdp_bh);
+	if (!gdp)
+		goto out_err;
+
+	ext4_lock_group(sb, group);
+	if (ext4_has_group_desc_csum(sb) &&
+	    (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) {
+		gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
+		ext4_free_group_clusters_set(sb, gdp,
+			ext4_free_clusters_after_init(sb, group, gdp));
+	}
+
+	already = 0;
+	for (i = 0; i < len; i++)
+		if (mb_test_bit(blkoff + i, bitmap_bh->b_data) ==
+				mc->state)
+			already++;
+	changed = len - already;
+
+	if (mc->state) {
+		mb_set_bits(bitmap_bh->b_data, blkoff, len);
+		ext4_free_group_clusters_set(sb, gdp,
+			ext4_free_group_clusters(sb, gdp) - changed);
+	} else {
+		mb_clear_bits(bitmap_bh->b_data, blkoff, len);
+		ext4_free_group_clusters_set(sb, gdp,
+			ext4_free_group_clusters(sb, gdp) + changed);
+	}
+
+	ext4_block_bitmap_csum_set(sb, gdp, bitmap_bh);
+	ext4_group_desc_csum_set(sb, group, gdp);
+	ext4_unlock_group(sb, group);
+
+	if (sbi->s_log_groups_per_flex) {
+		ext4_group_t flex_group = ext4_flex_group(sbi, group);
+		struct flex_groups *fg = sbi_array_rcu_deref(sbi,
+					   s_flex_groups, flex_group);
+
+		if (mc->state)
+			atomic64_sub(changed, &fg->free_clusters);
+		else
+			atomic64_add(changed, &fg->free_clusters);
+	}
+
+	err = ext4_handle_dirty_metadata(NULL, NULL, bitmap_bh);
+	if (err)
+		goto out_err;
+	err = ext4_handle_dirty_metadata(NULL, NULL, gdp_bh);
+	if (err)
+		goto out_err;
+
+	sync_dirty_buffer(bitmap_bh);
+	sync_dirty_buffer(gdp_bh);
+
+out_err:
+	brelse(bitmap_bh);
+	return err;
+}
 
 /*
  * Check quota and mark chosen space (ac->ac_b_ex) non-free in bitmaps
@@ -4078,16 +4172,14 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
 void ext4_mb_mark_bb(struct super_block *sb, ext4_fsblk_t block,
 			int len, int state)
 {
-	struct buffer_head *bitmap_bh = NULL;
-	struct ext4_group_desc *gdp;
-	struct buffer_head *gdp_bh;
+	struct ext4_mark_context mc;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	ext4_group_t group;
 	ext4_grpblk_t blkoff;
-	int i, err = 0;
-	int already;
-	unsigned int clen, clen_changed, thisgrp_len;
+	int err = 0;
+	unsigned int clen, thisgrp_len;
 
+	ext4_mb_prepare_mark_context(&mc, sb, state);
 	while (len > 0) {
 		ext4_get_group_no_and_offset(sb, block, &group, &blkoff);
 
@@ -4107,80 +4199,17 @@ void ext4_mb_mark_bb(struct super_block *sb, ext4_fsblk_t block,
 			ext4_error(sb, "Marking blocks in system zone - "
 				   "Block = %llu, len = %u",
 				   block, thisgrp_len);
-			bitmap_bh = NULL;
-			break;
-		}
-
-		bitmap_bh = ext4_read_block_bitmap(sb, group);
-		if (IS_ERR(bitmap_bh)) {
-			err = PTR_ERR(bitmap_bh);
-			bitmap_bh = NULL;
 			break;
 		}
 
-		err = -EIO;
-		gdp = ext4_get_group_desc(sb, group, &gdp_bh);
-		if (!gdp)
-			break;
-
-		ext4_lock_group(sb, group);
-		already = 0;
-		for (i = 0; i < clen; i++)
-			if (!mb_test_bit(blkoff + i, bitmap_bh->b_data) ==
-					 !state)
-				already++;
-
-		clen_changed = clen - already;
-		if (state)
-			mb_set_bits(bitmap_bh->b_data, blkoff, clen);
-		else
-			mb_clear_bits(bitmap_bh->b_data, blkoff, clen);
-		if (ext4_has_group_desc_csum(sb) &&
-		    (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) {
-			gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
-			ext4_free_group_clusters_set(sb, gdp,
-			     ext4_free_clusters_after_init(sb, group, gdp));
-		}
-		if (state)
-			clen = ext4_free_group_clusters(sb, gdp) - clen_changed;
-		else
-			clen = ext4_free_group_clusters(sb, gdp) + clen_changed;
-
-		ext4_free_group_clusters_set(sb, gdp, clen);
-		ext4_block_bitmap_csum_set(sb, gdp, bitmap_bh);
-		ext4_group_desc_csum_set(sb, group, gdp);
-
-		ext4_unlock_group(sb, group);
-
-		if (sbi->s_log_groups_per_flex) {
-			ext4_group_t flex_group = ext4_flex_group(sbi, group);
-			struct flex_groups *fg = sbi_array_rcu_deref(sbi,
-						   s_flex_groups, flex_group);
-
-			if (state)
-				atomic64_sub(clen_changed, &fg->free_clusters);
-			else
-				atomic64_add(clen_changed, &fg->free_clusters);
-
-		}
-
-		err = ext4_handle_dirty_metadata(NULL, NULL, bitmap_bh);
-		if (err)
-			break;
-		sync_dirty_buffer(bitmap_bh);
-		err = ext4_handle_dirty_metadata(NULL, NULL, gdp_bh);
-		sync_dirty_buffer(gdp_bh);
+		err = ext4_mb_mark_context(&mc, group, blkoff, clen);
 		if (err)
 			break;
 
 		block += thisgrp_len;
 		len -= thisgrp_len;
-		brelse(bitmap_bh);
 		BUG_ON(len < 0);
 	}
-
-	if (err)
-		brelse(bitmap_bh);
 }
 
 /*
-- 
2.30.0