Commit 57a45ced authored by Josef Bacik's avatar Josef Bacik
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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: default avatarJosef Bacik <josef@redhat.com>
parent 4a64001f

fs/btrfs/btrfs_inode.h

+1 −2
Original line number Original line Diff line number Diff line
@@ -136,9 +136,8 @@ struct btrfs_inode { 
	 * items we think we'll end up using, and reserved_extents is the number

	 * items we think we'll end up using, and reserved_extents is the number

	 * of extent items we've reserved metadata for.

	 * of extent items we've reserved metadata for.

	 */

	 */

	spinlock_t accounting_lock;

	atomic_t outstanding_extents;

	atomic_t outstanding_extents;

	int reserved_extents;

	atomic_t reserved_extents;





	/*

	/*

	 * ordered_data_close is set by truncate when a file that used

	 * ordered_data_close is set by truncate when a file that used

fs/btrfs/extent-tree.c

+26 −16
Original line number Original line Diff line number Diff line
@@ -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;

	struct btrfs_block_rsv *block_rsv = &root->fs_info->delalloc_block_rsv;

	u64 to_reserve;

	u64 to_reserve;

	int nr_extents;

	int nr_extents;

	int reserved_extents;

	int ret;

	int ret;





	if (btrfs_transaction_in_commit(root->fs_info))

	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);

	num_bytes = ALIGN(num_bytes, root->sectorsize);





	spin_lock(&BTRFS_I(inode)->accounting_lock);

	nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents) + 1;

	nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents) + 1;

	if (nr_extents > BTRFS_I(inode)->reserved_extents) {

	reserved_extents = atomic_read(&BTRFS_I(inode)->reserved_extents);

		nr_extents -= BTRFS_I(inode)->reserved_extents;



	if (nr_extents > reserved_extents) {

		nr_extents -= reserved_extents;

		to_reserve = calc_trans_metadata_size(root, nr_extents);

		to_reserve = calc_trans_metadata_size(root, nr_extents);

	} else {

	} else {

		nr_extents = 0;

		nr_extents = 0;

		to_reserve = 0;

		to_reserve = 0;

	}

	}

	spin_unlock(&BTRFS_I(inode)->accounting_lock);



	to_reserve += calc_csum_metadata_size(inode, num_bytes);

	to_reserve += calc_csum_metadata_size(inode, num_bytes);

	ret = reserve_metadata_bytes(NULL, root, block_rsv, to_reserve, 1);

	ret = reserve_metadata_bytes(NULL, root, block_rsv, to_reserve, 1);

	if (ret)

	if (ret)

		return ret;

		return ret;





	spin_lock(&BTRFS_I(inode)->accounting_lock);

	atomic_add(nr_extents, &BTRFS_I(inode)->reserved_extents);

	BTRFS_I(inode)->reserved_extents += nr_extents;

	atomic_inc(&BTRFS_I(inode)->outstanding_extents);

	atomic_inc(&BTRFS_I(inode)->outstanding_extents);

	spin_unlock(&BTRFS_I(inode)->accounting_lock);





	block_rsv_add_bytes(block_rsv, to_reserve, 1);

	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;

	struct btrfs_root *root = BTRFS_I(inode)->root;

	u64 to_free;

	u64 to_free;

	int nr_extents;

	int nr_extents;

	int reserved_extents;





	num_bytes = ALIGN(num_bytes, root->sectorsize);

	num_bytes = ALIGN(num_bytes, root->sectorsize);

	atomic_dec(&BTRFS_I(inode)->outstanding_extents);

	atomic_dec(&BTRFS_I(inode)->outstanding_extents);

	WARN_ON(atomic_read(&BTRFS_I(inode)->outstanding_extents) < 0);

	WARN_ON(atomic_read(&BTRFS_I(inode)->outstanding_extents) < 0);





	spin_lock(&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);

		nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents);

	if (nr_extents < BTRFS_I(inode)->reserved_extents) {

		if (nr_extents >= reserved_extents) {

		nr_extents = BTRFS_I(inode)->reserved_extents - nr_extents;

		BTRFS_I(inode)->reserved_extents -= nr_extents;

	} else {

			nr_extents = 0;

			nr_extents = 0;

			break;

		}

		}

	spin_unlock(&BTRFS_I(inode)->accounting_lock);

		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);

	to_free = calc_csum_metadata_size(inode, num_bytes);

	if (nr_extents > 0)

	if (nr_extents > 0)

fs/btrfs/inode.c

+2 −3
Original line number Original line Diff line number Diff line
@@ -6632,9 +6632,8 @@ struct inode *btrfs_alloc_inode(struct super_block *sb) 
	ei->index_cnt = (u64)-1;

	ei->index_cnt = (u64)-1;

	ei->last_unlink_trans = 0;

	ei->last_unlink_trans = 0;





	spin_lock_init(&ei->accounting_lock);

	atomic_set(&ei->outstanding_extents, 0);

	atomic_set(&ei->outstanding_extents, 0);

	ei->reserved_extents = 0;

	atomic_set(&ei->reserved_extents, 0);





	ei->ordered_data_close = 0;

	ei->ordered_data_close = 0;

	ei->orphan_meta_reserved = 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(!list_empty(&inode->i_dentry));

	WARN_ON(inode->i_data.nrpages);

	WARN_ON(inode->i_data.nrpages);

	WARN_ON(atomic_read(&BTRFS_I(inode)->outstanding_extents));

	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

	 * This can happen where we create an inode, but somebody else also

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