Btrfs: change reserved_extents to an atomic_t
We track delayed allocation per inodes via 2 counters, one is
outstanding_extents and reserved_extents. Outstanding_extents is already an
atomic_t, but reserved_extents is not and is protected by a spinlock. So
convert this to an atomic_t and instead of using a spinlock, use atomic_cmpxchg
when releasing delalloc bytes. This makes our inode 72 bytes smaller, and
reduces locking overhead (albiet it was minimal to begin with). Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 9007bbd..d97b69a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6632,9 +6632,8 @@
ei->index_cnt = (u64)-1;
ei->last_unlink_trans = 0;
- spin_lock_init(&ei->accounting_lock);
atomic_set(&ei->outstanding_extents, 0);
- ei->reserved_extents = 0;
+ atomic_set(&ei->reserved_extents, 0);
ei->ordered_data_close = 0;
ei->orphan_meta_reserved = 0;
@@ -6670,7 +6669,7 @@
WARN_ON(!list_empty(&inode->i_dentry));
WARN_ON(inode->i_data.nrpages);
WARN_ON(atomic_read(&BTRFS_I(inode)->outstanding_extents));
- WARN_ON(BTRFS_I(inode)->reserved_extents);
+ WARN_ON(atomic_read(&BTRFS_I(inode)->reserved_extents));
/*
* This can happen where we create an inode, but somebody else also