On 9 Feb 2021, at 23:28, Harshad Shirwadkar [off-list ref] wrote:

A few arrays in mballoc.c use the total number of valid orders as
their size. Currently, this value is set as "sb->s_blocksize_bits +
2". This makes code harder to read. So, instead add a new macro
MB_NUM_ORDERS(sb) to make the code more readable.

Signed-off-by: Harshad Shirwadkar <redacted>
Reviewed-by: Andreas Dilger <redacted>
---
fs/ext4/mballoc.c | 15 ++++++++-------
fs/ext4/mballoc.h |  5 +++++
2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index fffd0770e930..b7f25120547d 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c

@@ -756,7 +756,7 @@ mb_set_largest_free_order(struct super_block *sb, struct ext4_group_info *grp)

	grp->bb_largest_free_order = -1; /* uninit */

-	bits = sb->s_blocksize_bits + 1;
+	bits = MB_NUM_ORDERS(sb) - 1;
	for (i = bits; i >= 0; i--) {
		if (grp->bb_counters[i] > 0) {
			grp->bb_largest_free_order = i;

@@ -1928,7 +1928,7 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,

	int max;

	BUG_ON(ac->ac_2order <= 0);
-	for (i = ac->ac_2order; i <= sb->s_blocksize_bits + 1; i++) {
+	for (i = ac->ac_2order; i < MB_NUM_ORDERS(sb); i++) {
		if (grp->bb_counters[i] == 0)
			continue;

@@ -2314,13 +2314,13 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)

	 * We also support searching for power-of-two requests only for
	 * requests upto maximum buddy size we have constructed.
	 */
-	if (i >= sbi->s_mb_order2_reqs && i <= sb->s_blocksize_bits + 2) {
+	if (i >= sbi->s_mb_order2_reqs && i <= MB_NUM_ORDERS(sb)) {
		/*
		 * This should tell if fe_len is exactly power of 2
		 */
		if ((ac->ac_g_ex.fe_len & (~(1 << (i - 1)))) == 0)
			ac->ac_2order = array_index_nospec(i - 1,
-							   sb->s_blocksize_bits + 2);
+							   MB_NUM_ORDERS(sb));
	}

	/* if stream allocation is enabled, use global goal */

@@ -2850,7 +2850,7 @@ int ext4_mb_init(struct super_block *sb)

	unsigned max;
	int ret;

-	i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_offsets);
+	i = MB_NUM_ORDERS(sb) * sizeof(*sbi->s_mb_offsets);

	sbi->s_mb_offsets = kmalloc(i, GFP_KERNEL);
	if (sbi->s_mb_offsets == NULL) {

@@ -2858,7 +2858,7 @@ int ext4_mb_init(struct super_block *sb)

		goto out;
	}

-	i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_maxs);
+	i = MB_NUM_ORDERS(sb) * sizeof(*sbi->s_mb_maxs);
	sbi->s_mb_maxs = kmalloc(i, GFP_KERNEL);
	if (sbi->s_mb_maxs == NULL) {
		ret = -ENOMEM;

@@ -2884,7 +2884,8 @@ int ext4_mb_init(struct super_block *sb)

		offset_incr = offset_incr >> 1;
		max = max >> 1;
		i++;
-	} while (i <= sb->s_blocksize_bits + 1);
+	} while (i < MB_NUM_ORDERS(sb));
+

	spin_lock_init(&sbi->s_md_lock);
	sbi->s_mb_free_pending = 0;

diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 7597330dbdf8..02861406932f 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h

@@ -78,6 +78,11 @@
 */

#define MB_DEFAULT_MAX_INODE_PREALLOC	512

+/*
+ * Number of valid buddy orders
+ */
+#define MB_NUM_ORDERS(sb)		((sb)->s_blocksize_bits + 2)
+
struct ext4_free_data {
	/* this links the free block information from sb_info */
	struct list_head		efd_list;
-- 
2.30.0.478.g8a0d178c01-goog