Commit 20a5eab4 authored by Dave Chinner's avatar Dave Chinner
Browse files

xfs: convert xfs_ialloc_next_ag() to an atomic 



This is currently a spinlock lock protected rotor which can be
implemented with a single atomic operation. Change it to be more
efficient and get rid of the m_agirotor_lock. Noticed while
converting the inode allocation AG selection loop to active perag
references.

Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarAllison Henderson <allison.henderson@oracle.com>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
parent bab8b795

fs/xfs/libxfs/xfs_ialloc.c

+1 −16
Original line number Diff line number Diff line
@@ -1576,21 +1576,6 @@ xfs_dialloc_roll( 
	return error;

}



static xfs_agnumber_t

xfs_ialloc_next_ag(

	xfs_mount_t	*mp)

{

	xfs_agnumber_t	agno;



	spin_lock(&mp->m_agirotor_lock);

	agno = mp->m_agirotor;

	if (++mp->m_agirotor >= mp->m_maxagi)

		mp->m_agirotor = 0;

	spin_unlock(&mp->m_agirotor_lock);



	return agno;

}



static bool

xfs_dialloc_good_ag(

	struct xfs_perag	*pag,
@@ -1748,7 +1733,7 @@ xfs_dialloc( 
	 * an AG has enough space for file creation.

	 */

	if (S_ISDIR(mode))

		start_agno = xfs_ialloc_next_ag(mp);

		start_agno = atomic_inc_return(&mp->m_agirotor) % mp->m_maxagi;

	else {

		start_agno = XFS_INO_TO_AGNO(mp, parent);

		if (start_agno >= mp->m_maxagi)

fs/xfs/libxfs/xfs_sb.c

+2 −1
Original line number Diff line number Diff line
@@ -909,7 +909,8 @@ xfs_sb_mount_common( 
	struct xfs_mount	*mp,

	struct xfs_sb		*sbp)

{

	mp->m_agfrotor = mp->m_agirotor = 0;

	mp->m_agfrotor = 0;

	atomic_set(&mp->m_agirotor, 0);

	mp->m_maxagi = mp->m_sb.sb_agcount;

	mp->m_blkbit_log = sbp->sb_blocklog + XFS_NBBYLOG;

	mp->m_blkbb_log = sbp->sb_blocklog - BBSHIFT;

fs/xfs/xfs_mount.h

+1 −2
Original line number Diff line number Diff line
@@ -210,8 +210,7 @@ typedef struct xfs_mount { 
	struct xfs_error_cfg	m_error_cfg[XFS_ERR_CLASS_MAX][XFS_ERR_ERRNO_MAX];

	struct xstats		m_stats;	/* per-fs stats */

	xfs_agnumber_t		m_agfrotor;	/* last ag where space found */

	xfs_agnumber_t		m_agirotor;	/* last ag dir inode alloced */

	spinlock_t		m_agirotor_lock;/* .. and lock protecting it */

	atomic_t		m_agirotor;	/* last ag dir inode alloced */



	/* Memory shrinker to throttle and reprioritize inodegc */

	struct shrinker		m_inodegc_shrinker;

fs/xfs/xfs_super.c

+0 −1
Original line number Diff line number Diff line
@@ -1922,7 +1922,6 @@ static int xfs_init_fs_context( 
		return -ENOMEM;



	spin_lock_init(&mp->m_sb_lock);

	spin_lock_init(&mp->m_agirotor_lock);

	INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);

	spin_lock_init(&mp->m_perag_lock);

	mutex_init(&mp->m_growlock);