From: Filipe Manana Date: Fri, 17 Oct 2025 13:57:27 +0000 (+0100) Subject: btrfs: avoid recomputing used space in btrfs_try_granting_tickets() X-Git-Tag: v6.19-rc1~167^2~100 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=60532c2136ea205c5db0a622e1a51420c8530d0f;p=thirdparty%2Fkernel%2Flinux.git btrfs: avoid recomputing used space in btrfs_try_granting_tickets() In every iteration of the loop we call btrfs_space_info_used() which sums a bunch of fields from a space_info object. This implies doing a function call besides the sum, and we are holding the space_info's spinlock while we do this, so we want to keep the critical section as short as possible since that spinlock is used in all the code for space reservation and flushing (therefore it's heavily used). So call btrfs_try_granting_tickets() only once, before entering the loop, and then update it as we remove tickets. Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c index 8b1cf7f6c2231..c0bad6914bb7b 100644 --- a/fs/btrfs/space-info.c +++ b/fs/btrfs/space-info.c @@ -526,6 +526,7 @@ void btrfs_try_granting_tickets(struct btrfs_space_info *space_info) { struct list_head *head; enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_NO_FLUSH; + u64 used = btrfs_space_info_used(space_info, true); lockdep_assert_held(&space_info->lock); @@ -533,18 +534,20 @@ void btrfs_try_granting_tickets(struct btrfs_space_info *space_info) again: while (!list_empty(head)) { struct reserve_ticket *ticket; - u64 used = btrfs_space_info_used(space_info, true); + u64 used_after; ticket = list_first_entry(head, struct reserve_ticket, list); + used_after = used + ticket->bytes; /* Check and see if our ticket can be satisfied now. */ - if ((used + ticket->bytes <= space_info->total_bytes) || + if (used_after <= space_info->total_bytes || btrfs_can_overcommit(space_info, ticket->bytes, flush)) { btrfs_space_info_update_bytes_may_use(space_info, ticket->bytes); remove_ticket(space_info, ticket); ticket->bytes = 0; space_info->tickets_id++; wake_up(&ticket->wait); + used = used_after; } else { break; }