FAILED: patch "[PATCH] ext4: use buckets for cr 1 block scan instead of rbtree" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

83e80a6e3543 ("ext4: use buckets for cr 1 block scan instead of rbtree") 359745d78351 ("proc: remove PDE_DATA() completely")
6dfbbae14a7b ("fs: proc: store PDE()->data into inode->i_private") 87b93329fdd6 ("hwmon: (dell-smm) Unify i8k_ioctl() and i8k_ioctl_unlocked()") 024053877469 ("hwmon: (dell-smm) Simplify ioctl handler") 59a2ceeef6d6 ("Merge branch 'akpm' (patches from Andrew)")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 83e80a6e3543f37f74c8e48a5f305b054b65ce2a Mon Sep 17 00:00:00 2001
From: Jan Kara <[email protected]>
Date: Thu, 8 Sep 2022 11:21:28 +0200
Subject: [PATCH] ext4: use buckets for cr 1 block scan instead of rbtree

Using rbtree for sorting groups by average fragment size is relatively expensive (needs rbtree update on every block freeing or allocation) and leads to wide spreading of allocations because selection of block group is very sentitive both to changes in free space and amount of blocks allocated. Furthermore selecting group with the best matching average fragment size is not necessary anyway, even more so because the variability of fragment sizes within a group is likely large so average is not telling much. We just need a group with large enough average fragment size so that we have high probability of finding large enough free extent and we don't want average fragment size to be too big so that we are likely to find free extent only somewhat larger than what we need.

So instead of maintaing rbtree of groups sorted by fragment size keep bins (lists) or groups where average fragment size is in the interval [2^i, 2^(i+1)). This structure requires less updates on block allocation / freeing, generally avoids chaotic spreading of allocations into block groups, and still is able to quickly (even faster that the rbtree) provide a block group which is likely to have a suitably sized free space extent.

This patch reduces number of block groups used when untarring archive with medium sized files (size somewhat above 64k which is default mballoc limit for avoiding locality group preallocation) to about half and thus improves write speeds for eMMC flash significantly.

index 9bca5565547b..3bf9a6926798 100644
@@ -167,8 +167,6 @@ enum SHIFT_DIRECTION {
 #define EXT4_MB_CR0_OPTIMIZED		0x8000
 /* Avg fragment size rb tree lookup succeeded at least once for cr = 1 */
 #define EXT4_MB_CR1_OPTIMIZED		0x00010000
-/* Perform linear traversal for one group */
-#define EXT4_MB_SEARCH_NEXT_LINEAR	0x00020000
 struct ext4_allocation_request {
 	/* target inode for block we're allocating */
 	struct inode *inode;

@@ -1600,8 +1598,8 @@ struct ext4_sb_info {
 	struct list_head s_discard_list;
 	struct work_struct s_discard_work;
 	atomic_t s_retry_alloc_pending;
-	struct rb_root s_mb_avg_fragment_size_root;
-	rwlock_t s_mb_rb_lock;
+	struct list_head *s_mb_avg_fragment_size;
+	rwlock_t *s_mb_avg_fragment_size_locks;
 	struct list_head *s_mb_largest_free_orders;
 	rwlock_t *s_mb_largest_free_orders_locks;
 

@@ -3413,6 +3411,8 @@ struct ext4_group_info {
 	ext4_grpblk_t	bb_first_free;	/* first free block */
 	ext4_grpblk_t	bb_free;	/* total free blocks */
 	ext4_grpblk_t	bb_fragments;	/* nr of freespace fragments */
+	int		bb_avg_fragment_size_order;	/* order of average
+							   fragment in BG */
 	ext4_grpblk_t	bb_largest_free_order;/* order of largest frag in BG */
 	ext4_group_t	bb_group;	/* Group number */
 	struct          list_head bb_prealloc_list;

@@ -3420,7 +3420,7 @@ struct ext4_group_info {
 	void            *bb_bitmap;
 #endif
 	struct rw_semaphore alloc_sem;
-	struct rb_node	bb_avg_fragment_size_rb;
+	struct list_head bb_avg_fragment_size_node;
 	struct list_head bb_largest_free_order_node;
 	ext4_grpblk_t	bb_counters[];	/* Nr of free power-of-two-block
 					 * regions, index is order.

index 39da92ceabf8..dcda2a943cee 100644
@@ -178,7 +178,6 @@ struct ext4_allocation_context {
 	/* copy of the best found extent taken before preallocation efforts */
 	struct ext4_free_extent ac_f_ex;
 
-	ext4_group_t ac_last_optimal_group;
 	__u32 ac_groups_considered;
 	__u32 ac_flags;		/* allocation hints */
 	__u16 ac_groups_scanned;