linux-ext4 - [PATCH v3 5/5] ext4: open coding repeated check in next_linear

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Date: Wed, 24 Apr 2024 14:19:04 +0800
From: Kemeng Shi <shikemeng@...weicloud.com>
To: tytso@....edu,
	adilger.kernel@...ger.ca,
	linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: jack@...e.cz,
	ojaswin@...ux.ibm.com,
	ritesh.list@...il.com
Subject: [PATCH v3 5/5] ext4: open coding repeated check in next_linear_group

Open coding repeated check in next_linear_group.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
Reviewed-by: Jan Kara <jack@...e.cz>
---
 fs/ext4/mballoc.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 3d344a21b7f0..9f73a76d679a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1076,23 +1076,11 @@ static inline int should_optimize_scan(struct ext4_allocation_context *ac)
 }
 
 /*
- * Return next linear group for allocation. If linear traversal should not be
- * performed, this function just returns the same group
+ * Return next linear group for allocation.
  */
 static ext4_group_t
-next_linear_group(struct ext4_allocation_context *ac, ext4_group_t group,
-		  ext4_group_t ngroups)
+next_linear_group(ext4_group_t group, ext4_group_t ngroups)
 {
-	if (!should_optimize_scan(ac))
-		goto inc_and_return;
-
-	if (ac->ac_groups_linear_remaining) {
-		ac->ac_groups_linear_remaining--;
-		goto inc_and_return;
-	}
-
-	return group;
-inc_and_return:
 	/*
 	 * Artificially restricted ngroups for non-extent
 	 * files makes group > ngroups possible on first loop.
@@ -1118,8 +1106,19 @@ static void ext4_mb_choose_next_group(struct ext4_allocation_context *ac,
 {
 	*new_cr = ac->ac_criteria;
 
-	if (!should_optimize_scan(ac) || ac->ac_groups_linear_remaining) {
-		*group = next_linear_group(ac, *group, ngroups);
+	if (!should_optimize_scan(ac)) {
+		*group = next_linear_group(*group, ngroups);
+		return;
+	}
+
+	/*
+	 * Optimized scanning can return non adjacent groups which can cause
+	 * seek overhead for rotational disks. So try few linear groups before
+	 * trying optimized scan.
+	 */
+	if (ac->ac_groups_linear_remaining) {
+		*group = next_linear_group(*group, ngroups);
+		ac->ac_groups_linear_remaining--;
 		return;
 	}
 
-- 
2.30.0