[PATCH 45/58] xfs: create a separate workqueue for copy-on-write activities

Darrick J. Wong
2015-10-07T05:00:15Z

Create a separate workqueue to handle copy on write blocks so that we
don't explode the number of kworkers if a flood of writes comes
through. We could possibly use m_buf_wq for this too...

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_mount.h | 1 +
fs/xfs/xfs_super.c | 36 +++++++++++++++++++++++++++++++++++-
2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index aba42d7..6f4c335 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -142,6 +142,7 @@ typedef struct xfs_mount {
struct workqueue_struct *m_reclaim_workqueue;
struct workqueue_struct *m_log_workqueue;
struct workqueue_struct *m_eofblocks_workqueue;
+ struct workqueue_struct *m_cow_workqueue;

/*
* Generation of the filesysyem layout. This is incremented by each
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 6dc5993..c6a26b0 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -883,6 +883,33 @@ xfs_destroy_mount_workqueues(
destroy_workqueue(mp->m_buf_workqueue);
}

+STATIC int
+xfs_init_feature_workqueues(
+ struct xfs_mount *mp)
+{
+ if (xfs_sb_version_hasreflink(&mp->m_sb)) {
+ /* XXX awful, but it'll improve when bh's go away */
+ /* XXX probably need locking around the endio rbtree */
+ mp->m_cow_workqueue = alloc_workqueue("xfs-cow/%s",
+ WQ_MEM_RECLAIM|WQ_FREEZABLE|WQ_UNBOUND,
+ 1, mp->m_fsname);
+ if (!mp->m_cow_workqueue)
+ goto out;
+ }
+
+ return 0;
+out:
+ return -ENOMEM;
+}
+
+STATIC void
+xfs_destroy_feature_workqueues(
+ struct xfs_mount *mp)
+{
+ if (mp->m_cow_workqueue)
+ destroy_workqueue(mp->m_cow_workqueue);
+}
+
/*
* Flush all dirty data to disk. Must not be called while holding an XFS_ILOCK
* or a page lock. We use sync_inodes_sb() here to ensure we block while waiting
@@ -1490,6 +1517,10 @@ xfs_fs_fill_super(
if (error)
goto out_free_sb;

+ error = xfs_init_feature_workqueues(mp);
+ if (error)
+ goto out_filestream_unmount;
+
/*
* we must configure the block size in the superblock before we run the
* full mount process as the mount process can lookup and cache inodes.
@@ -1526,7 +1557,7 @@ xfs_fs_fill_super(

error = xfs_mountfs(mp);
if (error)
- goto out_filestream_unmount;
+ goto out_destroy_feature_workqueues;

root = igrab(VFS_I(mp->m_rootip));
if (!root) {
@@ -1541,6 +1572,8 @@ xfs_fs_fill_super(

return 0;

+out_destroy_feature_workqueues:
+ xfs_destroy_feature_workqueues(mp);
out_filestream_unmount:
xfs_filestream_unmount(mp);
out_free_sb:
@@ -1570,6 +1603,7 @@ xfs_fs_put_super(
struct xfs_mount *mp = XFS_M(sb);

xfs_notice(mp, "Unmounting Filesystem");
+ xfs_destroy_feature_workqueues(mp);
xfs_filestream_unmount(mp);
xfs_unmountfs(mp);