From ce129655c9d9aaa7b3bcc46529db1b36693575ed Mon Sep 17 00:00:00 2001 From: Wang Xiaoguang Date: Fri, 2 Sep 2016 10:58:46 +0800 Subject: btrfs: introduce tickets_id to determine whether asynchronous metadata reclaim work makes progress In btrfs_async_reclaim_metadata_space(), we use ticket's address to determine whether asynchronous metadata reclaim work is making progress. ticket = list_first_entry(&space_info->tickets, struct reserve_ticket, list); if (last_ticket == ticket) { flush_state++; } else { last_ticket = ticket; flush_state = FLUSH_DELAYED_ITEMS_NR; if (commit_cycles) commit_cycles--; } But indeed it's wrong, we should not rely on local variable's address to do this check, because addresses may be same. In my test environment, I dd one 168MB file in a 256MB fs, found that for this file, every time wait_reserve_ticket() called, local variable ticket's address is same, For above codes, assume a previous ticket's address is addrA, last_ticket is addrA. Btrfs_async_reclaim_metadata_space() finished this ticket and wake up it, then another ticket is added, but with the same address addrA, now last_ticket will be same to current ticket, then current ticket's flush work will start from current flush_state, not initial FLUSH_DELAYED_ITEMS_NR, which may result in some enospc issues(I have seen this in my test machine). Signed-off-by: Wang Xiaoguang Reviewed-by: Josef Bacik Signed-off-by: David Sterba --- fs/btrfs/ctree.h | 1 + fs/btrfs/extent-tree.c | 11 ++++++----- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index ec4154faab61..146d1c7078ed 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -427,6 +427,7 @@ struct btrfs_space_info { struct list_head ro_bgs; struct list_head priority_tickets; struct list_head tickets; + u64 tickets_id; struct rw_semaphore groups_sem; /* for block groups in our same type */ diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 4483487ef021..d09cf7aa083b 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -4966,12 +4966,12 @@ static void wake_all_tickets(struct list_head *head) */ static void btrfs_async_reclaim_metadata_space(struct work_struct *work) { - struct reserve_ticket *last_ticket = NULL; struct btrfs_fs_info *fs_info; struct btrfs_space_info *space_info; u64 to_reclaim; int flush_state; int commit_cycles = 0; + u64 last_tickets_id; fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work); space_info = __find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA); @@ -4984,8 +4984,7 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work) spin_unlock(&space_info->lock); return; } - last_ticket = list_first_entry(&space_info->tickets, - struct reserve_ticket, list); + last_tickets_id = space_info->tickets_id; spin_unlock(&space_info->lock); flush_state = FLUSH_DELAYED_ITEMS_NR; @@ -5005,10 +5004,10 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work) space_info); ticket = list_first_entry(&space_info->tickets, struct reserve_ticket, list); - if (last_ticket == ticket) { + if (last_tickets_id == space_info->tickets_id) { flush_state++; } else { - last_ticket = ticket; + last_tickets_id = space_info->tickets_id; flush_state = FLUSH_DELAYED_ITEMS_NR; if (commit_cycles) commit_cycles--; @@ -5384,6 +5383,7 @@ again: list_del_init(&ticket->list); num_bytes -= ticket->bytes; ticket->bytes = 0; + space_info->tickets_id++; wake_up(&ticket->wait); } else { ticket->bytes -= num_bytes; @@ -5426,6 +5426,7 @@ again: num_bytes -= ticket->bytes; space_info->bytes_may_use += ticket->bytes; ticket->bytes = 0; + space_info->tickets_id++; wake_up(&ticket->wait); } else { trace_btrfs_space_reservation(fs_info, "space_info", -- cgit