[PATCH v3 4/8] ext4: Move overlap assert logic into a separate function

Ojaswin Mujoo
2023-01-16T08:04:38Z

Abstract out the logic to double check for overlaps in normalize_pa to
a separate function. Since there has been no reports in past where we
have seen any overlaps which hits this bug_on(), in future we can
consider calling this function under "#ifdef AGGRESSIVE_CHECK" only.

There are no functional changes in this patch

Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
fs/ext4/mballoc.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index f4e699bce99f..1628b008a096 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3984,6 +3984,29 @@ static void ext4_mb_normalize_group_request(struct ext4_allocation_context *ac)
mb_debug(sb, "goal %u blocks for locality group\n", ac->ac_g_ex.fe_len);
}

+static inline void
+ext4_mb_pa_assert_overlap(struct ext4_allocation_context *ac,
+ ext4_lblk_t start, ext4_lblk_t end)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
+ struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
+ struct ext4_prealloc_space *tmp_pa;
+ ext4_lblk_t tmp_pa_start, tmp_pa_end;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {
+ spin_lock(&tmp_pa->pa_lock);
+ if (tmp_pa->pa_deleted == 0) {
+ tmp_pa_start = tmp_pa->pa_lstart;
+ tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);
+
+ BUG_ON(!(start >= tmp_pa_end || end <= tmp_pa_start));
+ }
+ spin_unlock(&tmp_pa->pa_lock);
+ }
+ rcu_read_unlock();
+}
+
/*
* Normalization means making request better in terms of
* size and alignment
@@ -4140,18 +4163,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
size = end - start;

/* XXX: extra loop to check we really don't overlap preallocations */
- rcu_read_lock();
- list_for_each_entry_rcu(tmp_pa, &ei->i_prealloc_list, pa_inode_list) {
- spin_lock(&tmp_pa->pa_lock);
- if (tmp_pa->pa_deleted == 0) {
- tmp_pa_start = tmp_pa->pa_lstart;
- tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);
-
- BUG_ON(!(start >= tmp_pa_end || end <= tmp_pa_start));
- }
- spin_unlock(&tmp_pa->pa_lock);
- }
- rcu_read_unlock();
+ ext4_mb_pa_assert_overlap(ac, start, end);

/*
* In this function "start" and "size" are normalized for better
--
2.31.1