linux-kernel - [RFC PATCH 2/7] exfat: support reuse buffer head for exfat_ent

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Message-ID: <20251118082208.1034186-3-chizhiling@163.com>
Date: Tue, 18 Nov 2025 16:22:03 +0800
From: Chi Zhiling <chizhiling@....com>
To: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Matthew Wilcox <willy@...radead.org>,
	Namjae Jeon <linkinjeon@...nel.org>,
	Sungjong Seo <sj1557.seo@...sung.com>,
	Yuezhang Mo <yuezhang.mo@...y.com>,
	Chi Zhiling <chizhiling@...inos.cn>
Subject: [RFC PATCH 2/7] exfat: support reuse buffer head for exfat_ent_get

From: Chi Zhiling <chizhiling@...inos.cn>

This patch is part 2 of cached buffer head for exfat_ent_get,
it introduces an argument for exfat_ent_get, and make sure this
routine releases buffer head refcount when any error return.

Signed-off-by: Chi Zhiling <chizhiling@...inos.cn>
---
 fs/exfat/cache.c    |  2 +-
 fs/exfat/exfat_fs.h |  4 ++--
 fs/exfat/fatent.c   | 35 +++++++++++++++++++++++------------
 3 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/fs/exfat/cache.c b/fs/exfat/cache.c
index d5ce0ae660ba..61af3fa05ab7 100644
--- a/fs/exfat/cache.c
+++ b/fs/exfat/cache.c
@@ -287,7 +287,7 @@ int exfat_get_cluster(struct inode *inode, unsigned int cluster,
 			return -EIO;
 		}
 
-		if (exfat_ent_get(sb, *dclus, &content))
+		if (exfat_ent_get(sb, *dclus, &content, NULL))
 			return -EIO;
 
 		*last_dclus = *dclus;
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 329697c89d09..d52893276e9a 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -433,13 +433,13 @@ int exfat_set_volume_dirty(struct super_block *sb);
 int exfat_clear_volume_dirty(struct super_block *sb);
 
 /* fatent.c */
-#define exfat_get_next_cluster(sb, pclu) exfat_ent_get(sb, *(pclu), pclu)
+#define exfat_get_next_cluster(sb, pclu) exfat_ent_get(sb, *(pclu), pclu, NULL)
 
 int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
 		struct exfat_chain *p_chain, bool sync_bmap);
 int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain);
 int exfat_ent_get(struct super_block *sb, unsigned int loc,
-		unsigned int *content);
+		unsigned int *content, struct buffer_head **last);
 int exfat_ent_set(struct super_block *sb, unsigned int loc,
 		unsigned int content);
 int exfat_chain_cont_cluster(struct super_block *sb, unsigned int chain,
diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
index f9c5d3485865..a3a19c8d2e05 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -88,8 +88,11 @@ int exfat_ent_set(struct super_block *sb, unsigned int loc,
 	return 0;
 }
 
+/*
+ * Caller must release the buffer_head if no error return.
+ */
 int exfat_ent_get(struct super_block *sb, unsigned int loc,
-		unsigned int *content)
+		unsigned int *content, struct buffer_head **last)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	int err;
@@ -98,39 +101,47 @@ int exfat_ent_get(struct super_block *sb, unsigned int loc,
 		exfat_fs_error_ratelimit(sb,
 			"invalid access to FAT (entry 0x%08x)",
 			loc);
-		return -EIO;
+		goto err;
 	}
 
-	err = __exfat_ent_get(sb, loc, content, NULL);
-	if (err) {
+	err = __exfat_ent_get(sb, loc, content, last);
+	if (unlikely(err)) {
 		exfat_fs_error_ratelimit(sb,
 			"failed to access to FAT (entry 0x%08x, err:%d)",
 			loc, err);
-		return err;
+		goto err;
 	}
 
-	if (*content == EXFAT_FREE_CLUSTER) {
+	if (unlikely(*content == EXFAT_FREE_CLUSTER)) {
 		exfat_fs_error_ratelimit(sb,
 			"invalid access to FAT free cluster (entry 0x%08x)",
 			loc);
-		return -EIO;
+		goto err;
 	}
 
-	if (*content == EXFAT_BAD_CLUSTER) {
+	if (unlikely(*content == EXFAT_BAD_CLUSTER)) {
 		exfat_fs_error_ratelimit(sb,
 			"invalid access to FAT bad cluster (entry 0x%08x)",
 			loc);
-		return -EIO;
+		goto err;
 	}
 
 	if (*content != EXFAT_EOF_CLUSTER && !is_valid_cluster(sbi, *content)) {
 		exfat_fs_error_ratelimit(sb,
 			"invalid access to FAT (entry 0x%08x) bogus content (0x%08x)",
 			loc, *content);
-		return -EIO;
+		goto err;
 	}
 
 	return 0;
+err:
+	if (last) {
+		brelse(*last);
+
+		/* Avoid double release */
+		*last = NULL;
+	}
+	return err;
 }
 
 int exfat_chain_cont_cluster(struct super_block *sb, unsigned int chain,
@@ -299,7 +310,7 @@ int exfat_find_last_cluster(struct super_block *sb, struct exfat_chain *p_chain,
 	do {
 		count++;
 		clu = next;
-		if (exfat_ent_get(sb, clu, &next))
+		if (exfat_ent_get(sb, clu, &next, NULL))
 			return -EIO;
 	} while (next != EXFAT_EOF_CLUSTER && count <= p_chain->size);
 
@@ -490,7 +501,7 @@ int exfat_count_num_clusters(struct super_block *sb,
 	count = 0;
 	for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters; i++) {
 		count++;
-		if (exfat_ent_get(sb, clu, &clu))
+		if (exfat_ent_get(sb, clu, &clu, NULL))
 			return -EIO;
 		if (clu == EXFAT_EOF_CLUSTER)
 			break;
-- 
2.43.0