linux-kernel - [PATCH 1/2] f2fs: avoid down_write on nat_tree

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Message-Id: <20211214182435.2595176-1-jaegeuk@kernel.org>
Date:   Tue, 14 Dec 2021 10:24:34 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>
Subject: [PATCH 1/2] f2fs: avoid down_write on nat_tree_lock during checkpoint

Let's cache nat entry if there's no lock contention only.

Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
 fs/f2fs/node.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 556fcd8457f3..b1bc7d76da3b 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -430,6 +430,10 @@ static void cache_nat_entry(struct f2fs_sb_info *sbi, nid_t nid,
 	struct f2fs_nm_info *nm_i = NM_I(sbi);
 	struct nat_entry *new, *e;
 
+	/* Let's mitigate lock contention of nat_tree_lock during checkpoint */
+	if (rwsem_is_locked(&sbi->cp_global_sem))
+		return;
+
 	new = __alloc_nat_entry(sbi, nid, false);
 	if (!new)
 		return;
-- 
2.34.1.173.g76aa8bc2d0-goog