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 <wangxg.fnst@cn.fujitsu.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ec4154f..146d1c7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -427,6 +427,7 @@
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 4483487..d09cf7a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4966,12 +4966,12 @@
*/
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 @@
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 @@
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 @@
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 @@
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",