[PATCH v3 3/6] exfat: use exfat_cluster_walk helper

Chi Zhiling
2026-04-03T08:06:49Z

Replace the custom exfat_walk_fat_chain() function and open-coded
FAT chain walking logic with the exfat_cluster_walk() helper across
exfat_find_location, __exfat_get_dentry_set, and exfat_map_cluster.

Suggested-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
---
fs/exfat/dir.c | 47 +++++++++++------------------------------------
fs/exfat/inode.c | 11 ++---------
2 files changed, 13 insertions(+), 45 deletions(-)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 7619410d668e..ca5827046a1f 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -562,38 +562,6 @@ int exfat_put_dentry_set(struct exfat_entry_set_cache *es, int sync)
return err;
}

-static int exfat_walk_fat_chain(struct super_block *sb,
- struct exfat_chain *p_dir, unsigned int byte_offset,
- unsigned int *clu)
-{
- struct exfat_sb_info *sbi = EXFAT_SB(sb);
- unsigned int clu_offset;
- unsigned int cur_clu;
-
- clu_offset = EXFAT_B_TO_CLU(byte_offset, sbi);
- cur_clu = p_dir->dir;
-
- if (p_dir->flags == ALLOC_NO_FAT_CHAIN) {
- cur_clu += clu_offset;
- } else {
- while (clu_offset > 0) {
- if (exfat_get_next_cluster(sb, &cur_clu))
- return -EIO;
- if (cur_clu == EXFAT_EOF_CLUSTER) {
- exfat_fs_error(sb,
- "invalid dentry access beyond EOF (clu : %u, eidx : %d)",
- p_dir->dir,
- EXFAT_B_TO_DEN(byte_offset));
- return -EIO;
- }
- clu_offset--;
- }
- }
-
- *clu = cur_clu;
- return 0;
-}
-
static int exfat_find_location(struct super_block *sb, struct exfat_chain *p_dir,
int entry, sector_t *sector, int *offset)
{
@@ -603,10 +571,19 @@ static int exfat_find_location(struct super_block *sb, struct exfat_chain *p_dir

off = EXFAT_DEN_TO_B(entry);

- ret = exfat_walk_fat_chain(sb, p_dir, off, &clu);
+ clu = p_dir->dir;
+ ret = exfat_cluster_walk(sb, &clu, EXFAT_B_TO_CLU(off, sbi), p_dir->flags);
if (ret)
return ret;

+ if (clu == EXFAT_EOF_CLUSTER) {
+ exfat_fs_error(sb,
+ "unexpected early break in cluster chain (clu : %u, len : %d)",
+ p_dir->dir,
+ EXFAT_B_TO_CLU(off, sbi));
+ return -EIO;
+ }
+
if (!exfat_test_bitmap(sb, clu)) {
exfat_err(sb, "failed to test cluster bit(%u)", clu);
return -EIO;
@@ -792,9 +769,7 @@ static int __exfat_get_dentry_set(struct exfat_entry_set_cache *es,
if (exfat_is_last_sector_in_cluster(sbi, sec)) {
unsigned int clu = exfat_sector_to_cluster(sbi, sec);

- if (p_dir->flags == ALLOC_NO_FAT_CHAIN)
- clu++;
- else if (exfat_get_next_cluster(sb, &clu))
+ if (exfat_cluster_walk(sb, &clu, 1, p_dir->flags))
goto put_es;
sec = exfat_cluster_to_sector(sbi, clu);
} else {
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index beb9ea7cca9f..cde2eb0f31ad 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -225,15 +225,8 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
* *clu = (the first cluster of the allocated chain) =>
* (the last cluster of ...)
*/
- if (ei->flags == ALLOC_NO_FAT_CHAIN) {
- *clu += num_to_be_allocated - 1;
- } else {
- while (num_to_be_allocated > 1) {
- if (exfat_get_next_cluster(sb, clu))
- return -EIO;
- num_to_be_allocated--;
- }
- }
+ if (exfat_cluster_walk(sb, clu, num_to_be_allocated - 1, ei->flags))
+ return -EIO;
*count = 1;
}

--
2.43.0