[RFC 04/11] ext4: Convert mballoc cr (criteria) to enum

Ojaswin Mujoo
2023-01-27T12:38:20Z

Convert criteria to be an enum so it easier to maintain. This change
also makes it easier to insert new criterias in the future.

Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
fs/ext4/ext4.h | 14 ++++++--
fs/ext4/mballoc.c | 88 +++++++++++++++++++++++------------------------
fs/ext4/mballoc.h | 10 ++++++
3 files changed, 65 insertions(+), 47 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b8b00457da8d..6037b8e0af86 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -126,6 +126,14 @@ enum SHIFT_DIRECTION {
SHIFT_RIGHT,
};

+/*
+ * Number of criterias defined. For each criteria, mballoc has slightly
+ * different way of finding the required blocks nad usually, higher the
+ * criteria the slower the allocation. We start at lower criterias and keep
+ * falling back to higher ones if we are not able to find any blocks.
+ */
+#define EXT4_MB_NUM_CRS 4
+
/*
* Flags used in mballoc's allocation_context flags field.
*
@@ -1631,9 +1639,9 @@ struct ext4_sb_info {
atomic_t s_bal_2orders; /* 2^order hits */
atomic_t s_bal_cr0_bad_suggestions;
atomic_t s_bal_cr1_bad_suggestions;
- atomic64_t s_bal_cX_groups_considered[4];
- atomic64_t s_bal_cX_hits[4];
- atomic64_t s_bal_cX_failed[4]; /* cX loop didn't find blocks */
+ atomic64_t s_bal_cX_groups_considered[EXT4_MB_NUM_CRS];
+ atomic64_t s_bal_cX_hits[EXT4_MB_NUM_CRS];
+ atomic64_t s_bal_cX_failed[EXT4_MB_NUM_CRS]; /* cX loop didn't find blocks */
atomic_t s_mb_buddies_generated; /* number of buddies generated */
atomic64_t s_mb_generation_time;
atomic_t s_mb_lost_chunks;
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 8b22cc07b054..323604a2ff45 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -409,7 +409,7 @@ static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac);

static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
- ext4_group_t group, int cr);
+ ext4_group_t group, enum criteria cr);

static int ext4_try_to_trim_range(struct super_block *sb,
struct ext4_buddy *e4b, ext4_grpblk_t start,
@@ -857,7 +857,7 @@ mb_update_avg_fragment_size(struct super_block *sb, struct ext4_group_info *grp)
* cr level needs an update.
*/
static void ext4_mb_choose_next_group_cr0(struct ext4_allocation_context *ac,
- int *new_cr, ext4_group_t *group, ext4_group_t ngroups)
+ enum criteria *new_cr, ext4_group_t *group, ext4_group_t ngroups)
{
struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
struct ext4_group_info *iter, *grp;
@@ -882,8 +882,8 @@ static void ext4_mb_choose_next_group_cr0(struct ext4_allocation_context *ac,
list_for_each_entry(iter, &sbi->s_mb_largest_free_orders[i],
bb_largest_free_order_node) {
if (sbi->s_mb_stats)
- atomic64_inc(&sbi->s_bal_cX_groups_considered[0]);
- if (likely(ext4_mb_good_group(ac, iter->bb_group, 0))) {
+ atomic64_inc(&sbi->s_bal_cX_groups_considered[CR0]);
+ if (likely(ext4_mb_good_group(ac, iter->bb_group, CR0))) {
grp = iter;
break;
}
@@ -895,7 +895,7 @@ static void ext4_mb_choose_next_group_cr0(struct ext4_allocation_context *ac,

if (!grp) {
/* Increment cr and search again */
- *new_cr = 1;
+ *new_cr = CR1;
} else {
*group = grp->bb_group;
ac->ac_flags |= EXT4_MB_CR0_OPTIMIZED;
@@ -907,7 +907,7 @@ static void ext4_mb_choose_next_group_cr0(struct ext4_allocation_context *ac,
* order. Updates *new_cr if cr level needs an update.
*/
static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac,
- int *new_cr, ext4_group_t *group, ext4_group_t ngroups)
+ enum criteria *new_cr, ext4_group_t *group, ext4_group_t ngroups)
{
struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
struct ext4_group_info *grp = NULL, *iter;
@@ -930,8 +930,8 @@ static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac,
list_for_each_entry(iter, &sbi->s_mb_avg_fragment_size[i],
bb_avg_fragment_size_node) {
if (sbi->s_mb_stats)
- atomic64_inc(&sbi->s_bal_cX_groups_considered[1]);
- if (likely(ext4_mb_good_group(ac, iter->bb_group, 1))) {
+ atomic64_inc(&sbi->s_bal_cX_groups_considered[CR1]);
+ if (likely(ext4_mb_good_group(ac, iter->bb_group, CR1))) {
grp = iter;
break;
}
@@ -945,7 +945,7 @@ static void ext4_mb_choose_next_group_cr1(struct ext4_allocation_context *ac,
*group = grp->bb_group;
ac->ac_flags |= EXT4_MB_CR1_OPTIMIZED;
} else {
- *new_cr = 2;
+ *new_cr = CR2;
}
}

@@ -953,7 +953,7 @@ static inline int should_optimize_scan(struct ext4_allocation_context *ac)
{
if (unlikely(!test_opt2(ac->ac_sb, MB_OPTIMIZE_SCAN)))
return 0;
- if (ac->ac_criteria >= 2)
+ if (ac->ac_criteria >= CR2)
return 0;
if (!ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS))
return 0;
@@ -998,7 +998,7 @@ next_linear_group(struct ext4_allocation_context *ac, int group, int ngroups)
* @ngroups Total number of groups
*/
static void ext4_mb_choose_next_group(struct ext4_allocation_context *ac,
- int *new_cr, ext4_group_t *group, ext4_group_t ngroups)
+ enum criteria *new_cr, ext4_group_t *group, ext4_group_t ngroups)
{
*new_cr = ac->ac_criteria;

@@ -1007,9 +1007,9 @@ static void ext4_mb_choose_next_group(struct ext4_allocation_context *ac,
return;
}

- if (*new_cr == 0) {
+ if (*new_cr == CR0) {
ext4_mb_choose_next_group_cr0(ac, new_cr, group, ngroups);
- } else if (*new_cr == 1) {
+ } else if (*new_cr == CR1) {
ext4_mb_choose_next_group_cr1(ac, new_cr, group, ngroups);
} else {
/*
@@ -2378,13 +2378,13 @@ void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,
* for the allocation or not.
*/
static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
- ext4_group_t group, int cr)
+ ext4_group_t group, enum criteria cr)
{
ext4_grpblk_t free, fragments;
int flex_size = ext4_flex_bg_size(EXT4_SB(ac->ac_sb));
struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);

- BUG_ON(cr < 0 || cr >= 4);
+ BUG_ON(cr < CR0 || cr >= EXT4_MB_NUM_CRS);

if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
return false;
@@ -2398,7 +2398,7 @@ static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
return false;

switch (cr) {
- case 0:
+ case CR0:
BUG_ON(ac->ac_2order == 0);

/* Avoid using the first bg of a flexgroup for data files */
@@ -2417,15 +2417,15 @@ static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
return false;

return true;
- case 1:
+ case CR1:
if ((free / fragments) >= ac->ac_g_ex.fe_len)
return true;
break;
- case 2:
+ case CR2:
if (free >= ac->ac_g_ex.fe_len)
return true;
break;
- case 3:
+ case CR3:
return true;
default:
BUG();
@@ -2446,7 +2446,7 @@ static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
* out"!
*/
static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
- ext4_group_t group, int cr)
+ ext4_group_t group, enum criteria cr)
{
struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);
struct super_block *sb = ac->ac_sb;
@@ -2464,7 +2464,7 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
free = grp->bb_free;
if (free == 0)
goto out;
- if (cr <= 2 && free < ac->ac_g_ex.fe_len)
+ if (cr <= CR2 && free < ac->ac_g_ex.fe_len)
goto out;
if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
goto out;
@@ -2479,7 +2479,7 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
ext4_get_group_desc(sb, group, NULL);
int ret;

- /* cr=0/1 is a very optimistic search to find large
+ /* cr=CR0/CR1 is a very optimistic search to find large
* good chunks almost for free. If buddy data is not
* ready, then this optimization makes no sense. But
* we never skip the first block group in a flex_bg,
@@ -2487,7 +2487,7 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
* and we want to make sure we locate metadata blocks
* in the first block group in the flex_bg if possible.
*/
- if (cr < 2 &&
+ if (cr < CR2 &&
(!sbi->s_log_groups_per_flex ||
((group & ((1 << sbi->s_log_groups_per_flex) - 1)) != 0)) &&
!(ext4_has_group_desc_csum(sb) &&
@@ -2593,7 +2593,7 @@ static noinline_for_stack int
ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
{
ext4_group_t prefetch_grp = 0, ngroups, group, i;
- int cr = -1, new_cr;
+ enum criteria cr, new_cr;
int err = 0, first_err = 0;
unsigned int nr = 0, prefetch_ios = 0;
struct ext4_sb_info *sbi;
@@ -2651,13 +2651,13 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
}

/* Let's just scan groups to find more-less suitable blocks */
- cr = ac->ac_2order ? 0 : 1;
+ cr = ac->ac_2order ? CR0 : CR1;
/*
- * cr == 0 try to get exact allocation,
- * cr == 3 try to get anything
+ * cr == CR0 try to get exact allocation,
+ * cr == CR3 try to get anything
*/
repeat:
- for (; cr < 4 && ac->ac_status == AC_STATUS_CONTINUE; cr++) {
+ for (; cr < EXT4_MB_NUM_CRS && ac->ac_status == AC_STATUS_CONTINUE; cr++) {
ac->ac_criteria = cr;
/*
* searching for the right group start
@@ -2684,7 +2684,7 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
* spend a lot of time loading imperfect groups
*/
if ((prefetch_grp == group) &&
- (cr > 1 ||
+ (cr > CR1 ||
prefetch_ios < sbi->s_mb_prefetch_limit)) {
unsigned int curr_ios = prefetch_ios;

@@ -2726,9 +2726,9 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
}

ac->ac_groups_scanned++;
- if (cr == 0)
+ if (cr == CR0)
ext4_mb_simple_scan_group(ac, &e4b);
- else if (cr == 1 && sbi->s_stripe &&
+ else if (cr == CR1 && sbi->s_stripe &&
!(ac->ac_g_ex.fe_len % sbi->s_stripe))
ext4_mb_scan_aligned(ac, &e4b);
else
@@ -2768,7 +2768,7 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
ac->ac_b_ex.fe_len = 0;
ac->ac_status = AC_STATUS_CONTINUE;
ac->ac_flags |= EXT4_MB_HINT_FIRST;
- cr = 3;
+ cr = CR3;
goto repeat;
}
}
@@ -2891,36 +2891,36 @@ int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset)
seq_printf(seq, "\tgroups_scanned: %u\n", atomic_read(&sbi->s_bal_groups_scanned));

seq_puts(seq, "\tcr0_stats:\n");
- seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[0]));
+ seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[CR0]));
seq_printf(seq, "\t\tgroups_considered: %llu\n",
- atomic64_read(&sbi->s_bal_cX_groups_considered[0]));
+ atomic64_read(&sbi->s_bal_cX_groups_considered[CR0]));
seq_printf(seq, "\t\tuseless_loops: %llu\n",
- atomic64_read(&sbi->s_bal_cX_failed[0]));
+ atomic64_read(&sbi->s_bal_cX_failed[CR0]));
seq_printf(seq, "\t\tbad_suggestions: %u\n",
atomic_read(&sbi->s_bal_cr0_bad_suggestions));

seq_puts(seq, "\tcr1_stats:\n");
- seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[1]));
+ seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[CR1]));
seq_printf(seq, "\t\tgroups_considered: %llu\n",
- atomic64_read(&sbi->s_bal_cX_groups_considered[1]));
+ atomic64_read(&sbi->s_bal_cX_groups_considered[CR1]));
seq_printf(seq, "\t\tuseless_loops: %llu\n",
- atomic64_read(&sbi->s_bal_cX_failed[1]));
+ atomic64_read(&sbi->s_bal_cX_failed[CR1]));
seq_printf(seq, "\t\tbad_suggestions: %u\n",
atomic_read(&sbi->s_bal_cr1_bad_suggestions));

seq_puts(seq, "\tcr2_stats:\n");
- seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[2]));
+ seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[CR2]));
seq_printf(seq, "\t\tgroups_considered: %llu\n",
- atomic64_read(&sbi->s_bal_cX_groups_considered[2]));
+ atomic64_read(&sbi->s_bal_cX_groups_considered[CR2]));
seq_printf(seq, "\t\tuseless_loops: %llu\n",
- atomic64_read(&sbi->s_bal_cX_failed[2]));
+ atomic64_read(&sbi->s_bal_cX_failed[CR2]));

seq_puts(seq, "\tcr3_stats:\n");
- seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[3]));
+ seq_printf(seq, "\t\thits: %llu\n", atomic64_read(&sbi->s_bal_cX_hits[CR3]));
seq_printf(seq, "\t\tgroups_considered: %llu\n",
- atomic64_read(&sbi->s_bal_cX_groups_considered[3]));
+ atomic64_read(&sbi->s_bal_cX_groups_considered[CR3]));
seq_printf(seq, "\t\tuseless_loops: %llu\n",
- atomic64_read(&sbi->s_bal_cX_failed[3]));
+ atomic64_read(&sbi->s_bal_cX_failed[CR3]));
seq_printf(seq, "\textents_scanned: %u\n", atomic_read(&sbi->s_bal_ex_scanned));
seq_printf(seq, "\t\tgoal_hits: %u\n", atomic_read(&sbi->s_bal_goals));
seq_printf(seq, "\t\t2^n_hits: %u\n", atomic_read(&sbi->s_bal_2orders));
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 165a17893c81..f0087a85e366 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -95,6 +95,16 @@
*/
#define MB_NUM_ORDERS(sb) ((sb)->s_blocksize_bits + 2)

+/*
+ * All possible allocation criterias for mballoc
+ */
+enum criteria {
+ CR0,
+ CR1,
+ CR2,
+ CR3,
+};
+
struct ext4_free_data {
/* this links the free block information from sb_info */
struct list_head efd_list;
--
2.31.1