This is a note to let you know that I've just added the patch titled
ext4: drop s_mb_bal_lock and convert protected fields to atomic
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-drop-s_mb_bal_lock-and-convert-protected-fields.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 8fa6eeecde84fc767348b00b4286f4258bb1ed2b
Author: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
Date: Thu Apr 1 10:21:23 2021 -0700
ext4: drop s_mb_bal_lock and convert protected fields to atomic
[ Upstream commit 67d25186046145748d5fe4c5019d832215e01c1e ]
s_mb_buddies_generated gets used later in this patch series to
determine if the cr 0 and cr 1 optimziations should be performed or
not. Currently, s_mb_buddies_generated is protected under a
spin_lock. In the allocation path, it is better if we don't depend on
the lock and instead read the value atomically. In order to do that,
we drop s_bal_lock altogether and we convert the only two protected
fields by it s_mb_buddies_generated and s_mb_generation_time to atomic
type.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@xxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
Reviewed-by: Ritesh Harjani <ritesh.list@xxxxxxxxx>
Link: https://lore.kernel.org/r/20210401172129.189766-2-harshadshirwadkar@xxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Stable-dep-of: 5354b2af3406 ("ext4: allow ext4_get_group_info() to fail")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 246573a4e8041..5efd48d7c9a79 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1538,9 +1538,8 @@ struct ext4_sb_info {
atomic_t s_bal_goals; /* goal hits */
atomic_t s_bal_breaks; /* too long searches */
atomic_t s_bal_2orders; /* 2^order hits */
- spinlock_t s_bal_lock;
- unsigned long s_mb_buddies_generated;
- unsigned long long s_mb_generation_time;
+ atomic_t s_mb_buddies_generated; /* number of buddies generated */
+ atomic64_t s_mb_generation_time;
atomic_t s_mb_lost_chunks;
atomic_t s_mb_preallocated;
atomic_t s_mb_discarded;
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 708a5fa3c69f6..beee54480562a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -816,10 +816,8 @@ void ext4_mb_generate_buddy(struct super_block *sb,
clear_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
period = get_cycles() - period;
- spin_lock(&sbi->s_bal_lock);
- sbi->s_mb_buddies_generated++;
- sbi->s_mb_generation_time += period;
- spin_unlock(&sbi->s_bal_lock);
+ atomic_inc(&sbi->s_mb_buddies_generated);
+ atomic64_add(period, &sbi->s_mb_generation_time);
}
/* The buddy information is attached the buddy cache inode
@@ -2855,7 +2853,6 @@ int ext4_mb_init(struct super_block *sb)
} while (i <= sb->s_blocksize_bits + 1);
spin_lock_init(&sbi->s_md_lock);
- spin_lock_init(&sbi->s_bal_lock);
sbi->s_mb_free_pending = 0;
INIT_LIST_HEAD(&sbi->s_freed_data_list);
@@ -2991,9 +2988,9 @@ int ext4_mb_release(struct super_block *sb)
atomic_read(&sbi->s_bal_breaks),
atomic_read(&sbi->s_mb_lost_chunks));
ext4_msg(sb, KERN_INFO,
- "mballoc: %lu generated and it took %Lu",
- sbi->s_mb_buddies_generated,
- sbi->s_mb_generation_time);
+ "mballoc: %u generated and it took %llu",
+ atomic_read(&sbi->s_mb_buddies_generated),
+ atomic64_read(&sbi->s_mb_generation_time));
ext4_msg(sb, KERN_INFO,
"mballoc: %u preallocated, %u discarded",
atomic_read(&sbi->s_mb_preallocated),
