Commit daa5611c authored by NeilBrown's avatar NeilBrown Committed by Greg Kroah-Hartman
Browse files

staging: lustre: fid: convert lcs_mutex to a spinlock 



There is only one place where this lock is held
while the task might sleep - in
  ldebugfs_fid_space_seq_write()
while ldebugfs_fid_write_common() is called.

This call can easily be taken out of the locked region
by asking it to parse the user data into a local variable,
and then copying that variable into ->lcs_space while
holding the lock.

Note that ldebugfs_gid_write_common returns >0 on
success, so use that to gate updating ->lcs_space.

So make that change, and convert lcs_mutex to a spinlock
named lcs_lock.  spinlocks are slightly cheaper than mutexes
and using one makes is clear that the lock is only held for
a short time.

Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ef8e5dbb

drivers/staging/lustre/lustre/fid/fid_request.c

+12 −12
Original line number Diff line number Diff line
@@ -198,24 +198,24 @@ static int seq_fid_alloc_prep(struct lu_client_seq *seq, 
	if (seq->lcs_update) {

		add_wait_queue(&seq->lcs_waitq, link);

		set_current_state(TASK_UNINTERRUPTIBLE);

		mutex_unlock(&seq->lcs_mutex);

		spin_unlock(&seq->lcs_lock);



		schedule();



		mutex_lock(&seq->lcs_mutex);

		spin_lock(&seq->lcs_lock);

		remove_wait_queue(&seq->lcs_waitq, link);

		set_current_state(TASK_RUNNING);

		return -EAGAIN;

	}

	++seq->lcs_update;

	mutex_unlock(&seq->lcs_mutex);

	spin_unlock(&seq->lcs_lock);

	return 0;

}



static void seq_fid_alloc_fini(struct lu_client_seq *seq)

{

	LASSERT(seq->lcs_update == 1);

	mutex_lock(&seq->lcs_mutex);

	spin_lock(&seq->lcs_lock);

	--seq->lcs_update;

	wake_up(&seq->lcs_waitq);

}
@@ -231,7 +231,7 @@ int seq_client_alloc_fid(const struct lu_env *env, 
	LASSERT(fid);



	init_waitqueue_entry(&link, current);

	mutex_lock(&seq->lcs_mutex);

	spin_lock(&seq->lcs_lock);



	if (OBD_FAIL_CHECK(OBD_FAIL_SEQ_EXHAUST))

		seq->lcs_fid.f_oid = seq->lcs_width;
@@ -256,7 +256,7 @@ int seq_client_alloc_fid(const struct lu_env *env, 
			CERROR("%s: Can't allocate new sequence, rc %d\n",

			       seq->lcs_name, rc);

			seq_fid_alloc_fini(seq);

			mutex_unlock(&seq->lcs_mutex);

			spin_unlock(&seq->lcs_lock);

			return rc;

		}
@@ -278,7 +278,7 @@ int seq_client_alloc_fid(const struct lu_env *env, 
	}



	*fid = seq->lcs_fid;

	mutex_unlock(&seq->lcs_mutex);

	spin_unlock(&seq->lcs_lock);



	CDEBUG(D_INFO,

	       "%s: Allocated FID " DFID "\n", seq->lcs_name,  PFID(fid));
@@ -296,16 +296,16 @@ void seq_client_flush(struct lu_client_seq *seq) 


	LASSERT(seq);

	init_waitqueue_entry(&link, current);

	mutex_lock(&seq->lcs_mutex);

	spin_lock(&seq->lcs_lock);



	while (seq->lcs_update) {

		add_wait_queue(&seq->lcs_waitq, &link);

		set_current_state(TASK_UNINTERRUPTIBLE);

		mutex_unlock(&seq->lcs_mutex);

		spin_unlock(&seq->lcs_lock);



		schedule();



		mutex_lock(&seq->lcs_mutex);

		spin_lock(&seq->lcs_lock);

		remove_wait_queue(&seq->lcs_waitq, &link);

		set_current_state(TASK_RUNNING);

	}
@@ -319,7 +319,7 @@ void seq_client_flush(struct lu_client_seq *seq) 
	seq->lcs_space.lsr_index = -1;



	lu_seq_range_init(&seq->lcs_space);

	mutex_unlock(&seq->lcs_mutex);

	spin_unlock(&seq->lcs_lock);

}

EXPORT_SYMBOL(seq_client_flush);
@@ -382,7 +382,7 @@ static int seq_client_init(struct lu_client_seq *seq, 


	seq->lcs_type = type;



	mutex_init(&seq->lcs_mutex);

	spin_lock_init(&seq->lcs_lock);

	if (type == LUSTRE_SEQ_METADATA)

		seq->lcs_width = LUSTRE_METADATA_SEQ_MAX_WIDTH;

	else

drivers/staging/lustre/lustre/fid/lproc_fid.c

+16 −13
Original line number Diff line number Diff line
@@ -98,20 +98,23 @@ ldebugfs_fid_space_seq_write(struct file *file, 
			     size_t count, loff_t *off)

{

	struct lu_client_seq *seq;

	struct lu_seq_range range;

	int rc;



	seq = ((struct seq_file *)file->private_data)->private;



	mutex_lock(&seq->lcs_mutex);

	rc = ldebugfs_fid_write_common(buffer, count, &seq->lcs_space);

	rc = ldebugfs_fid_write_common(buffer, count, &range);



	spin_lock(&seq->lcs_lock);

	if (rc > 0)

		seq->lcs_space = range;

	spin_unlock(&seq->lcs_lock);



	if (rc == 0) {

		CDEBUG(D_INFO, "%s: Space: " DRANGE "\n",

		       seq->lcs_name, PRANGE(&seq->lcs_space));

		       seq->lcs_name, PRANGE(&range));

	}



	mutex_unlock(&seq->lcs_mutex);



	return count;

}
@@ -120,9 +123,9 @@ ldebugfs_fid_space_seq_show(struct seq_file *m, void *unused) 
{

	struct lu_client_seq *seq = (struct lu_client_seq *)m->private;



	mutex_lock(&seq->lcs_mutex);

	spin_lock(&seq->lcs_lock);

	seq_printf(m, "[%#llx - %#llx]:%x:%s\n", PRANGE(&seq->lcs_space));

	mutex_unlock(&seq->lcs_mutex);

	spin_unlock(&seq->lcs_lock);



	return 0;

}
@@ -142,7 +145,7 @@ ldebugfs_fid_width_seq_write(struct file *file, 
	if (rc)

		return rc;



	mutex_lock(&seq->lcs_mutex);

	spin_lock(&seq->lcs_lock);

	if (seq->lcs_type == LUSTRE_SEQ_DATA)

		max = LUSTRE_DATA_SEQ_MAX_WIDTH;

	else
@@ -155,7 +158,7 @@ ldebugfs_fid_width_seq_write(struct file *file, 
		       seq->lcs_width);

	}



	mutex_unlock(&seq->lcs_mutex);

	spin_unlock(&seq->lcs_lock);



	return count;

}
@@ -165,9 +168,9 @@ ldebugfs_fid_width_seq_show(struct seq_file *m, void *unused) 
{

	struct lu_client_seq *seq = (struct lu_client_seq *)m->private;



	mutex_lock(&seq->lcs_mutex);

	spin_lock(&seq->lcs_lock);

	seq_printf(m, "%llu\n", seq->lcs_width);

	mutex_unlock(&seq->lcs_mutex);

	spin_unlock(&seq->lcs_lock);



	return 0;

}
@@ -177,9 +180,9 @@ ldebugfs_fid_fid_seq_show(struct seq_file *m, void *unused) 
{

	struct lu_client_seq *seq = (struct lu_client_seq *)m->private;



	mutex_lock(&seq->lcs_mutex);

	spin_lock(&seq->lcs_lock);

	seq_printf(m, DFID "\n", PFID(&seq->lcs_fid));

	mutex_unlock(&seq->lcs_mutex);

	spin_unlock(&seq->lcs_lock);



	return 0;

}

drivers/staging/lustre/lustre/include/lustre_fid.h

+1 −1
Original line number Diff line number Diff line
@@ -324,7 +324,7 @@ enum lu_mgr_type { 
struct lu_client_seq {

	/* Sequence-controller export. */

	struct obd_export      *lcs_exp;

	struct mutex		lcs_mutex;

	spinlock_t		lcs_lock;



	/*

	 * Range of allowed for allocation sequences. When using lu_client_seq on

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