From 007145ff644cc9a2b2b0c3c88ba68824274fcb12 Mon Sep 17 00:00:00 2001 From: Filipe Manana 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 Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/space-info.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) 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 v1.2.3