[PATCH 16/21] staging: lustre: fid: convert lcs_mutex to a spinlock
From: NeilBrown
Date: Mon Feb 19 2018 - 21:26:20 EST
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: NeilBrown <neilb@xxxxxxxx>
---
drivers/staging/lustre/lustre/fid/fid_request.c | 24 ++++++++---------
drivers/staging/lustre/lustre/fid/lproc_fid.c | 29 +++++++++++---------
drivers/staging/lustre/lustre/include/lustre_fid.h | 2 +
3 files changed, 29 insertions(+), 26 deletions(-)
diff --git a/drivers/staging/lustre/lustre/fid/fid_request.c b/drivers/staging/lustre/lustre/fid/fid_request.c
index 009c2367f74e..6b9d024bd27b 100644
--- a/drivers/staging/lustre/lustre/fid/fid_request.c
+++ b/drivers/staging/lustre/lustre/fid/fid_request.c
@@ -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
diff --git a/drivers/staging/lustre/lustre/fid/lproc_fid.c b/drivers/staging/lustre/lustre/fid/lproc_fid.c
index 083419f77697..e05487662afd 100644
--- a/drivers/staging/lustre/lustre/fid/lproc_fid.c
+++ b/drivers/staging/lustre/lustre/fid/lproc_fid.c
@@ -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;
}
diff --git a/drivers/staging/lustre/lustre/include/lustre_fid.h b/drivers/staging/lustre/lustre/include/lustre_fid.h
index d19c7a27ee48..094ad282de2c 100644
--- a/drivers/staging/lustre/lustre/include/lustre_fid.h
+++ b/drivers/staging/lustre/lustre/include/lustre_fid.h
@@ -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