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Btrfs: change reserved_extents to an atomic_t

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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>
This commit is contained in:
Josef Bacik
2011-01-25 16:30:38 -05:00
parent 4a64001f00
commit 57a45ced94
3 changed files with 29 additions and 21 deletions
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5
fs/btrfs/inode.c
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@@ -6632,9 +6632,8 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
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 @@ void btrfs_destroy_inode(struct inode *inode)
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