From:   Kemeng Shi <shikemeng@huaweicloud.com>
To:     tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz,
        ojaswin@linux.ibm.com, ritesh.list@gmail.com
Cc:     linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        shikemeng@huaweicloud.com
Subject: [PATCH v2 04/20] ext4: correct calculation of s_mb_preallocated
Date:   Tue, 28 Feb 2023 19:42:50 +0800
Message-Id: <20230228114306.3328235-5-shikemeng@huaweicloud.com>
In-Reply-To: <20230228114306.3328235-1-shikemeng@huaweicloud.com>
References: <20230228114306.3328235-1-shikemeng@huaweicloud.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

We will add pa_free to s_mb_preallocated when new ext4_prealloc_space is
created. In ext4_mb_new_inode_pa, we will call ext4_mb_use_inode_pa
before adding pa_free to s_mb_preallocated. However, ext4_mb_use_inode_pa
will consume pa_free for block allocation which triggerred the creation
of ext4_prealloc_space. Add pa_free to s_mb_preallocated before
ext4_mb_use_inode_pa to correct calculation of s_mb_preallocated.
There is no such problem in ext4_mb_new_group_pa as pa_free of group pa
is consumed in ext4_mb_release_context instead of ext4_mb_use_group_pa.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
---
 fs/ext4/mballoc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index b94c9f331a3c..90f765a350ea 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4667,8 +4667,8 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
 		 pa->pa_len, pa->pa_lstart);
 	trace_ext4_mb_new_inode_pa(ac, pa);
 
-	ext4_mb_use_inode_pa(ac, pa);
 	atomic_add(pa->pa_free, &sbi->s_mb_preallocated);
+	ext4_mb_use_inode_pa(ac, pa);
 
 	ei = EXT4_I(ac->ac_inode);
 	grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);
-- 
2.30.0