From 57a45ced94fe48a701361d64230fc16eefa189dd Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Tue, 25 Jan 2011 16:30:38 -0500 Subject: [PATCH] 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 --- fs/btrfs/btrfs_inode.h | 3 +-- fs/btrfs/extent-tree.c | 42 ++++++++++++++++++++++++++---------------- fs/btrfs/inode.c | 5 ++--- 3 files changed, 29 insertions(+), 21 deletions(-) diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h index ccc991c542df..57c3bb2884ce 100644 --- a/fs/btrfs/btrfs_inode.h +++ b/fs/btrfs/btrfs_inode.h @@ -136,9 +136,8 @@ struct btrfs_inode { * items we think we'll end up using, and reserved_extents is the number * of extent items we've reserved metadata for. */ - spinlock_t accounting_lock; atomic_t outstanding_extents; - int reserved_extents; + atomic_t reserved_extents; /* * ordered_data_close is set by truncate when a file that used diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 7b3089b5c2df..27376c97d85f 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3996,6 +3996,7 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes) struct btrfs_block_rsv *block_rsv = &root->fs_info->delalloc_block_rsv; u64 to_reserve; int nr_extents; + int reserved_extents; int ret; if (btrfs_transaction_in_commit(root->fs_info)) @@ -4003,25 +4004,24 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes) num_bytes = ALIGN(num_bytes, root->sectorsize); - spin_lock(&BTRFS_I(inode)->accounting_lock); nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents) + 1; - if (nr_extents > BTRFS_I(inode)->reserved_extents) { - nr_extents -= BTRFS_I(inode)->reserved_extents; + reserved_extents = atomic_read(&BTRFS_I(inode)->reserved_extents); + + if (nr_extents > reserved_extents) { + nr_extents -= reserved_extents; to_reserve = calc_trans_metadata_size(root, nr_extents); } else { nr_extents = 0; to_reserve = 0; } - spin_unlock(&BTRFS_I(inode)->accounting_lock); + to_reserve += calc_csum_metadata_size(inode, num_bytes); ret = reserve_metadata_bytes(NULL, root, block_rsv, to_reserve, 1); if (ret) return ret; - spin_lock(&BTRFS_I(inode)->accounting_lock); - BTRFS_I(inode)->reserved_extents += nr_extents; + atomic_add(nr_extents, &BTRFS_I(inode)->reserved_extents); atomic_inc(&BTRFS_I(inode)->outstanding_extents); - spin_unlock(&BTRFS_I(inode)->accounting_lock); block_rsv_add_bytes(block_rsv, to_reserve, 1); @@ -4036,20 +4036,30 @@ void btrfs_delalloc_release_metadata(struct inode *inode, u64 num_bytes) struct btrfs_root *root = BTRFS_I(inode)->root; u64 to_free; int nr_extents; + int reserved_extents; num_bytes = ALIGN(num_bytes, root->sectorsize); atomic_dec(&BTRFS_I(inode)->outstanding_extents); WARN_ON(atomic_read(&BTRFS_I(inode)->outstanding_extents) < 0); - spin_lock(&BTRFS_I(inode)->accounting_lock); - nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents); - if (nr_extents < BTRFS_I(inode)->reserved_extents) { - nr_extents = BTRFS_I(inode)->reserved_extents - nr_extents; - BTRFS_I(inode)->reserved_extents -= nr_extents; - } else { - nr_extents = 0; - } - spin_unlock(&BTRFS_I(inode)->accounting_lock); + reserved_extents = atomic_read(&BTRFS_I(inode)->reserved_extents); + do { + int old, new; + + nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents); + if (nr_extents >= reserved_extents) { + nr_extents = 0; + break; + } + old = reserved_extents; + nr_extents = reserved_extents - nr_extents; + new = reserved_extents - nr_extents; + old = atomic_cmpxchg(&BTRFS_I(inode)->reserved_extents, + reserved_extents, new); + if (likely(old == reserved_extents)) + break; + reserved_extents = old; + } while (1); to_free = calc_csum_metadata_size(inode, num_bytes); if (nr_extents > 0) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 9007bbd01dbf..d97b69afbbfb 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -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