linux-kernel - [PATCH] f2fs: Avoid double lock for cp

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Message-Id: <1587636832-17939-1-git-send-email-sayalil@codeaurora.org>
Date:   Thu, 23 Apr 2020 15:43:52 +0530
From:   Sayali Lokhande <sayalil@...eaurora.org>
To:     jaegeuk@...nel.org, yuchao0@...wei.com,
        linux-f2fs-devel@...ts.sourceforge.net
Cc:     stummala@...eaurora.org, linux-kernel@...r.kernel.org,
        Sayali Lokhande <sayalil@...eaurora.org>
Subject: [PATCH] f2fs: Avoid double lock for cp_rwsem

Call stack :
f2fs_write_checkpoint()
-> block_operations(sbi)
    f2fs_lock_all(sbi);
     down_write(&sbi->cp_rwsem); => write lock held
<>
-> f2fs_sync_node_pages()
    if (is_inline_node(page))
     flush_inline_data()
	page = f2fs_pagecache_get_page()
         if (!page)
           goto iput_out;
	iput_out:
	 iput(inode);
          -> f2fs_evict_inode()
	      f2fs_truncate_blocks()
	       f2fs_lock_op()
	        down_read(&sbi->cp_rwsem); => read lock fail

Signed-off-by: Sayali Lokhande <sayalil@...eaurora.org>
---
 fs/f2fs/checkpoint.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 5ba649e..5c504cf 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1219,21 +1219,19 @@ static int block_operations(struct f2fs_sb_info *sbi)
 		goto retry_flush_quotas;
 	}
 
-retry_flush_nodes:
 	down_write(&sbi->node_write);
 
 	if (get_pages(sbi, F2FS_DIRTY_NODES)) {
 		up_write(&sbi->node_write);
+		f2fs_unlock_all(sbi);
 		atomic_inc(&sbi->wb_sync_req[NODE]);
 		err = f2fs_sync_node_pages(sbi, &wbc, false, FS_CP_NODE_IO);
 		atomic_dec(&sbi->wb_sync_req[NODE]);
-		if (err) {
-			up_write(&sbi->node_change);
-			f2fs_unlock_all(sbi);
+		up_write(&sbi->node_change);
+		if (err)
 			goto out;
-		}
 		cond_resched();
-		goto retry_flush_nodes;
+		goto retry_flush_quotas;
 	}
 
 	/*
-- 
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