From 007145ff644cc9a2b2b0c3c88ba68824274fcb12 Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@suse.com>
Date: Tue, 21 Mar 2023 11:13:52 +0000
Subject: btrfs: accurately calculate number of delayed refs when flushing
When flushing a limited number of delayed references (FLUSH_DELAYED_REFS_NR
state), we are assuming each delayed reference is holding a number of bytes
matching the needed space for inserting for a single metadata item (the
result of btrfs_calc_insert_metadata_size()). That is not correct when
using the free space tree, as in that case we have to multiply that value
by 2 since we need to touch the free space tree as well. This is the same
computation as we do at btrfs_update_delayed_refs_rsv() and at
btrfs_delayed_refs_rsv_release().
So correct the computation for the amount of delayed references we need to
flush in case we have the free space tree. This does not fix a functional
issue, instead it makes the flush code flush less delayed references, only
the minimum necessary to satisfy a ticket.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/space-info.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
(limited to 'fs/btrfs/space-info.c')
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 5eb161d96e35..f36b16ee0a02 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -550,6 +550,30 @@ static inline u64 calc_reclaim_items_nr(struct btrfs_fs_info *fs_info,
return nr;
}
+static inline u64 calc_delayed_refs_nr(struct btrfs_fs_info *fs_info,
+ u64 to_reclaim)
+{
+ u64 bytes;
+ u64 nr;
+
+ bytes = btrfs_calc_insert_metadata_size(fs_info, 1);
+ /*
+ * We have to check the mount option here because we could be enabling
+ * the free space tree for the first time and don't have the compat_ro
+ * option set yet.
+ *
+ * We need extra reservations if we have the free space tree because
+ * we'll have to modify that tree as well.
+ */
+ if (btrfs_test_opt(fs_info, FREE_SPACE_TREE))
+ bytes *= 2;
+
+ nr = div64_u64(to_reclaim, bytes);
+ if (!nr)
+ nr = 1;
+ return nr;
+}
+
#define EXTENT_SIZE_PER_ITEM SZ_256K
/*
@@ -727,7 +751,7 @@ static void flush_space(struct btrfs_fs_info *fs_info,
break;
}
if (state == FLUSH_DELAYED_REFS_NR)
- nr = calc_reclaim_items_nr(fs_info, num_bytes);
+ nr = calc_delayed_refs_nr(fs_info, num_bytes);
else
nr = 0;
btrfs_run_delayed_refs(trans, nr);
--
cgit