Patch "btrfs: zoned: optimize hint byte for zoned allocator" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    btrfs: zoned: optimize hint byte for zoned allocator

to the 6.6-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:
     btrfs-zoned-optimize-hint-byte-for-zoned-allocator.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a5b54315a09611fe06f64cef6372f5cf69ec1829
Author: Naohiro Aota <naohiro.aota@xxxxxxx>
Date:   Tue Dec 19 01:02:29 2023 +0900

    btrfs: zoned: optimize hint byte for zoned allocator
    
    [ Upstream commit 02444f2ac26eae6385a65fcd66915084d15dffba ]
    
    Writing sequentially to a huge file on btrfs on a SMR HDD revealed a
    decline of the performance (220 MiB/s to 30 MiB/s after 500 minutes).
    
    The performance goes down because of increased latency of the extent
    allocation, which is induced by a traversing of a lot of full block groups.
    
    So, this patch optimizes the ffe_ctl->hint_byte by choosing a block group
    with sufficient size from the active block group list, which does not
    contain full block groups.
    
    After applying the patch, the performance is maintained well.
    
    Fixes: 2eda57089ea3 ("btrfs: zoned: implement sequential extent allocation")
    CC: stable@xxxxxxxxxxxxxxx # 5.15+
    Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
    Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx>
    Signed-off-by: David Sterba <dsterba@xxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 69abb6eb81df..b89b558b1592 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4152,6 +4152,24 @@ static int prepare_allocation_zoned(struct btrfs_fs_info *fs_info,
 		if (fs_info->data_reloc_bg)
 			ffe_ctl->hint_byte = fs_info->data_reloc_bg;
 		spin_unlock(&fs_info->relocation_bg_lock);
+	} else if (ffe_ctl->flags & BTRFS_BLOCK_GROUP_DATA) {
+		struct btrfs_block_group *block_group;
+
+		spin_lock(&fs_info->zone_active_bgs_lock);
+		list_for_each_entry(block_group, &fs_info->zone_active_bgs, active_bg_list) {
+			/*
+			 * No lock is OK here because avail is monotinically
+			 * decreasing, and this is just a hint.
+			 */
+			u64 avail = block_group->zone_capacity - block_group->alloc_offset;
+
+			if (block_group_bits(block_group, ffe_ctl->flags) &&
+			    avail >= ffe_ctl->num_bytes) {
+				ffe_ctl->hint_byte = block_group->start;
+				break;
+			}
+		}
+		spin_unlock(&fs_info->zone_active_bgs_lock);
 	}
 
 	return 0;