[PATCH 6.12 076/265] ext4: factor out ext4_mb_scan_group()

Greg Kroah-Hartman
2026-03-12T20:16:25Z

From: Baokun Li <libaokun1@huawei.com>

[ Upstream commit 9c08e42db9056d423dcef5e7998c73182180ff83 ]

Extract ext4_mb_scan_group() to make the code clearer and to
prepare for the later conversion of 'choose group' to 'scan groups'.
No functional changes.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20250714130327.1830534-15-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Stable-dep-of: 4865c768b563 ("ext4: always allocate blocks only from groups inode can use")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ext4/mballoc.c | 93 +++++++++++++++++++++++++----------------------
fs/ext4/mballoc.h | 2 +
2 files changed, 51 insertions(+), 44 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index af014b43d0b3f..03c0886da0571 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2861,12 +2861,56 @@ void ext4_mb_prefetch_fini(struct super_block *sb, ext4_group_t group,
}
}

+static int ext4_mb_scan_group(struct ext4_allocation_context *ac,
+ ext4_group_t group)
+{
+ int ret;
+ struct super_block *sb = ac->ac_sb;
+ enum criteria cr = ac->ac_criteria;
+
+ ext4_mb_might_prefetch(ac, group);
+
+ /* prevent unnecessary buddy loading. */
+ if (cr < CR_ANY_FREE && spin_is_locked(ext4_group_lock_ptr(sb, group)))
+ return 0;
+
+ /* This now checks without needing the buddy page */
+ ret = ext4_mb_good_group_nolock(ac, group, cr);
+ if (ret <= 0) {
+ if (!ac->ac_first_err)
+ ac->ac_first_err = ret;
+ return 0;
+ }
+
+ ret = ext4_mb_load_buddy(sb, group, ac->ac_e4b);
+ if (ret)
+ return ret;
+
+ /* skip busy group */
+ if (cr >= CR_ANY_FREE)
+ ext4_lock_group(sb, group);
+ else if (!ext4_try_lock_group(sb, group))
+ goto out_unload;
+
+ /* We need to check again after locking the block group. */
+ if (unlikely(!ext4_mb_good_group(ac, group, cr)))
+ goto out_unlock;
+
+ __ext4_mb_scan_group(ac);
+
+out_unlock:
+ ext4_unlock_group(sb, group);
+out_unload:
+ ext4_mb_unload_buddy(ac->ac_e4b);
+ return ret;
+}
+
static noinline_for_stack int
ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
{
ext4_group_t ngroups, group, i;
enum criteria new_cr, cr = CR_GOAL_LEN_FAST;
- int err = 0, first_err = 0;
+ int err = 0;
struct ext4_sb_info *sbi;
struct super_block *sb;
struct ext4_buddy e4b;
@@ -2928,6 +2972,7 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)

ac->ac_e4b = &e4b;
ac->ac_prefetch_ios = 0;
+ ac->ac_first_err = 0;
repeat:
for (; cr < EXT4_MB_NUM_CRS && ac->ac_status == AC_STATUS_CONTINUE; cr++) {
ac->ac_criteria = cr;
@@ -2942,7 +2987,6 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)

for (i = 0, new_cr = cr; i < ngroups; i++,
ext4_mb_choose_next_group(ac, &new_cr, &group, ngroups)) {
- int ret = 0;

cond_resched();
if (new_cr != cr) {
@@ -2950,49 +2994,10 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
goto repeat;
}

- ext4_mb_might_prefetch(ac, group);
-
- /* prevent unnecessary buddy loading. */
- if (cr < CR_ANY_FREE &&
- spin_is_locked(ext4_group_lock_ptr(sb, group)))
- continue;
-
- /* This now checks without needing the buddy page */
- ret = ext4_mb_good_group_nolock(ac, group, cr);
- if (ret <= 0) {
- if (!first_err)
- first_err = ret;
- continue;
- }
-
- err = ext4_mb_load_buddy(sb, group, &e4b);
+ err = ext4_mb_scan_group(ac, group);
if (err)
goto out;

- /* skip busy group */
- if (cr >= CR_ANY_FREE) {
- ext4_lock_group(sb, group);
- } else if (!ext4_try_lock_group(sb, group)) {
- ext4_mb_unload_buddy(&e4b);
- continue;
- }
-
- /*
- * We need to check again after locking the
- * block group
- */
- ret = ext4_mb_good_group(ac, group, cr);
- if (ret == 0) {
- ext4_unlock_group(sb, group);
- ext4_mb_unload_buddy(&e4b);
- continue;
- }
-
- __ext4_mb_scan_group(ac);
-
- ext4_unlock_group(sb, group);
- ext4_mb_unload_buddy(&e4b);
-
if (ac->ac_status != AC_STATUS_CONTINUE)
break;
}
@@ -3037,8 +3042,8 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
if (sbi->s_mb_stats && ac->ac_status == AC_STATUS_FOUND)
atomic64_inc(&sbi->s_bal_cX_hits[ac->ac_criteria]);
out:
- if (!err && ac->ac_status != AC_STATUS_FOUND && first_err)
- err = first_err;
+ if (!err && ac->ac_status != AC_STATUS_FOUND && ac->ac_first_err)
+ err = ac->ac_first_err;

mb_debug(sb, "Best len %d, origin len %d, ac_status %u, ac_flags 0x%x, cr %d ret %d\n",
ac->ac_b_ex.fe_len, ac->ac_o_ex.fe_len, ac->ac_status,
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 9f66b1d5db67a..83886fc9521b7 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -196,6 +196,8 @@ struct ext4_allocation_context {
unsigned int ac_prefetch_ios;
unsigned int ac_prefetch_nr;

+ int ac_first_err;
+
__u32 ac_flags; /* allocation hints */
__u32 ac_groups_linear_remaining;
__u16 ac_groups_scanned;
--
2.51.0