[PATCH V2] ubifs: correct UBIFS_DFS_DIR_LEN macro definition and improve code clarity
From: ZhaoLong Wang
Date: Mon Mar 25 2024 - 11:31:49 EST
The UBIFS_DFS_DIR_LEN macro, which defines the maximum length of the UBIFS
debugfs directory name, has an incorrect formula and misleading comments.
The current formula is (3 + 1 + 2*2 + 1), which assumes that both UBI device
number and volume ID are limited to 2 characters. However, UBI device number
ranges from 0 to 37 (2 characters), and volume ID ranges from 0 to 127 (up
to 3 characters).
Although the current code works due to the cancellation of mathematical
errors (9 + 1 = 10, which matches the correct UBIFS_DFS_DIR_LEN value), it
can lead to confusion and potential issues in the future.
This patch aims to improve the code clarity and maintainability by making
the following changes:
1. Corrects the UBIFS_DFS_DIR_LEN macro definition to (3 + 1 + 2 + 3 + 1),
accommodating the maximum lengths of both UBI device number and volume ID,
plus the separators and null terminator.
2. Updates the snprintf calls to use UBIFS_DFS_DIR_LEN instead of
UBIFS_DFS_DIR_LEN + 1, removing the unnecessary +1.
3. Modifies the error checks to compare against UBIFS_DFS_DIR_LEN using >=
instead of >, aligning with the corrected macro definition.
4. Removes the redundant +1 in the dfs_dir_name array definitions in ubi.h
and debug.h.
5. Renames the duplicated UBIFS_DFS_DIR_LEN and UBIFS_DFS_DIR_NAME macros in
the sysfs-related code (sysfs.c and ubifs.h) to UBIFS_SYSFS_DIR_LEN and
UBIFS_SYSFS_DIR_NAME, respectively, to differentiate their usage from the
debugfs constants.
While these changes do not affect the runtime behavior, they make the code
more readable, maintainable, and less prone to future errors.
Signed-off-by: ZhaoLong Wang <wangzhaolong1@xxxxxxxxxx>
---
drivers/mtd/ubi/debug.c | 4 ++--
drivers/mtd/ubi/ubi.h | 2 +-
fs/ubifs/debug.c | 4 ++--
fs/ubifs/debug.h | 7 ++++---
fs/ubifs/sysfs.c | 6 +++---
fs/ubifs/ubifs.h | 7 ++++---
6 files changed, 16 insertions(+), 14 deletions(-)
diff --git a/drivers/mtd/ubi/debug.c b/drivers/mtd/ubi/debug.c
index d57f52bd2ff3..9ec3b8b6a0aa 100644
--- a/drivers/mtd/ubi/debug.c
+++ b/drivers/mtd/ubi/debug.c
@@ -598,9 +598,9 @@ int ubi_debugfs_init_dev(struct ubi_device *ubi)
if (!IS_ENABLED(CONFIG_DEBUG_FS))
return 0;
- n = snprintf(d->dfs_dir_name, UBI_DFS_DIR_LEN + 1, UBI_DFS_DIR_NAME,
+ n = snprintf(d->dfs_dir_name, UBI_DFS_DIR_LEN, UBI_DFS_DIR_NAME,
ubi->ubi_num);
- if (n > UBI_DFS_DIR_LEN) {
+ if (n >= UBI_DFS_DIR_LEN) {
/* The array size is too small */
return -EINVAL;
}
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 32009a24869e..da4e53ef5b0a 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -420,7 +420,7 @@ struct ubi_debug_info {
unsigned int power_cut_min;
unsigned int power_cut_max;
unsigned int emulate_failures;
- char dfs_dir_name[UBI_DFS_DIR_LEN + 1];
+ char dfs_dir_name[UBI_DFS_DIR_LEN];
struct dentry *dfs_dir;
struct dentry *dfs_chk_gen;
struct dentry *dfs_chk_io;
diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index ac77ac1fd73e..d91cec93d968 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -2827,9 +2827,9 @@ void dbg_debugfs_init_fs(struct ubifs_info *c)
const char *fname;
struct ubifs_debug_info *d = c->dbg;
- n = snprintf(d->dfs_dir_name, UBIFS_DFS_DIR_LEN + 1, UBIFS_DFS_DIR_NAME,
+ n = snprintf(d->dfs_dir_name, UBIFS_DFS_DIR_LEN, UBIFS_DFS_DIR_NAME,
c->vi.ubi_num, c->vi.vol_id);
- if (n > UBIFS_DFS_DIR_LEN) {
+ if (n >= UBIFS_DFS_DIR_LEN) {
/* The array size is too small */
return;
}
diff --git a/fs/ubifs/debug.h b/fs/ubifs/debug.h
index ed966108da80..d425861e6b82 100644
--- a/fs/ubifs/debug.h
+++ b/fs/ubifs/debug.h
@@ -19,10 +19,11 @@ typedef int (*dbg_znode_callback)(struct ubifs_info *c,
/*
* The UBIFS debugfs directory name pattern and maximum name length (3 for "ubi"
- * + 1 for "_" and plus 2x2 for 2 UBI numbers and 1 for the trailing zero byte.
+ * + 1 for "_" and 2 for UBI device numbers and 3 for volume number and 1 for
+ * the trailing zero byte.
*/
#define UBIFS_DFS_DIR_NAME "ubi%d_%d"
-#define UBIFS_DFS_DIR_LEN (3 + 1 + 2*2 + 1)
+#define UBIFS_DFS_DIR_LEN (3 + 1 + 2 + 3 + 1)
/**
* ubifs_debug_info - per-FS debugging information.
@@ -103,7 +104,7 @@ struct ubifs_debug_info {
unsigned int chk_fs:1;
unsigned int tst_rcvry:1;
- char dfs_dir_name[UBIFS_DFS_DIR_LEN + 1];
+ char dfs_dir_name[UBIFS_DFS_DIR_LEN];
struct dentry *dfs_dir;
struct dentry *dfs_dump_lprops;
struct dentry *dfs_dump_budg;
diff --git a/fs/ubifs/sysfs.c b/fs/ubifs/sysfs.c
index 1c958148bb87..7b30aac42ac5 100644
--- a/fs/ubifs/sysfs.c
+++ b/fs/ubifs/sysfs.c
@@ -91,17 +91,17 @@ static struct kset ubifs_kset = {
int ubifs_sysfs_register(struct ubifs_info *c)
{
int ret, n;
- char dfs_dir_name[UBIFS_DFS_DIR_LEN+1];
+ char dfs_dir_name[UBIFS_SYSFS_DIR_LEN];
c->stats = kzalloc(sizeof(struct ubifs_stats_info), GFP_KERNEL);
if (!c->stats) {
ret = -ENOMEM;
goto out_last;
}
- n = snprintf(dfs_dir_name, UBIFS_DFS_DIR_LEN + 1, UBIFS_DFS_DIR_NAME,
+ n = snprintf(dfs_dir_name, UBIFS_SYSFS_DIR_LEN, UBIFS_SYSFS_DIR_NAME,
c->vi.ubi_num, c->vi.vol_id);
- if (n > UBIFS_DFS_DIR_LEN) {
+ if (n >= UBIFS_SYSFS_DIR_LEN) {
/* The array size is too small */
ret = -EINVAL;
goto out_free;
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 1f3ea879d93a..549e147c5ce5 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -159,10 +159,11 @@
/*
* The UBIFS sysfs directory name pattern and maximum name length (3 for "ubi"
- * + 1 for "_" and plus 2x2 for 2 UBI numbers and 1 for the trailing zero byte.
+ * + 1 for "_" and 2 for UBI device numbers and 3 for volume number and 1 for
+ * the trailing zero byte.
*/
-#define UBIFS_DFS_DIR_NAME "ubi%d_%d"
-#define UBIFS_DFS_DIR_LEN (3 + 1 + 2*2 + 1)
+#define UBIFS_SYSFS_DIR_NAME "ubi%d_%d"
+#define UBIFS_SYSFS_DIR_LEN (3 + 1 + 2 + 3 + 1)
/*
* Lockdep classes for UBIFS inode @ui_mutex.
--
2.31.1