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scoutfs: don't use delayed downconvert work

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The delayed downconvert work wasn't being canceled on shutdown.  60s
after unmount at least the net lock's timer would fire and crash trying
to queue the delayed work on the destroyed workqueue.

Proactively unlocking the locks isn't always beneficial to begin with.
The relative costs of mispredicting the future are wildly different if
we have to re-read item caches from segments or have to downconvert a
blocking read lock.

So we can just remove the delayed work to fix the bug and remove a
moving piece that would need to be considered and tuned.  There's still
a race where we can get basts after destroying the workqueue but before
we destroy the lockspace, we'll get there.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2017-07-19 13:30:03 -07:00
parent 47b26d7888
commit 13ebd8d18c
2 changed files with 14 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kmod/src/lock.c
+13 -17
View File
@@ -97,7 +97,8 @@ static void put_scoutfs_lock(struct super_block *sb, struct scoutfs_lock *lock)
refs = --lock->refcnt;
if (!refs) {
BUG_ON(lock->holders);
BUG_ON(delayed_work_pending(&lock->dc_work));
/* can't be (even racy) busy without refs */
BUG_ON(work_busy(&lock->dc_work));
rb_erase(&lock->node, &linfo->lock_tree);
list_del(&lock->lru_entry);
spin_unlock(&linfo->lock);
@@ -128,8 +129,7 @@ static struct scoutfs_lock *alloc_scoutfs_lock(struct super_block *sb,
lock->sb = sb;
lock->lock_name = *lock_name;
lock->mode = DLM_LOCK_IV;
INIT_DELAYED_WORK(&lock->dc_work,
scoutfs_downconvert_func);
INIT_WORK(&lock->dc_work, scoutfs_downconvert_func);
INIT_LIST_HEAD(&lock->lru_entry);
}
}
@@ -279,24 +279,24 @@ static void scoutfs_ast(void *astarg)
}
static void queue_blocking_work(struct lock_info *linfo,
struct scoutfs_lock *lock, unsigned int seconds)
struct scoutfs_lock *lock)
{
assert_spin_locked(&linfo->lock);
if (!(lock->flags & SCOUTFS_LOCK_QUEUED)) {
/* Take a ref for the workqueue */
lock->flags |= SCOUTFS_LOCK_QUEUED;
lock->refcnt++;
queue_work(linfo->downconvert_wq, &lock->dc_work);
}
mod_delayed_work(linfo->downconvert_wq, &lock->dc_work, seconds * HZ);
}
static void set_lock_blocking(struct lock_info *linfo, struct scoutfs_lock *lock,
unsigned int seconds)
static void set_lock_blocking(struct lock_info *linfo,
struct scoutfs_lock *lock)
{
assert_spin_locked(&linfo->lock);
lock->flags |= SCOUTFS_LOCK_BLOCKING;
if (lock->holders == 0)
queue_blocking_work(linfo, lock, seconds);
queue_blocking_work(linfo, lock);
}
static void scoutfs_bast(void *astarg, int mode)
@@ -307,7 +307,7 @@ static void scoutfs_bast(void *astarg, int mode)
trace_scoutfs_bast(lock->sb, lock);
spin_lock(&linfo->lock);
set_lock_blocking(linfo, lock, 0);
set_lock_blocking(linfo, lock);
spin_unlock(&linfo->lock);
}
@@ -381,7 +381,7 @@ check_lock_state:
* blocking to let the downconvert thread do it's work
* so we can reacquire at the correct mode.
*/
set_lock_blocking(linfo, lock, 0);
set_lock_blocking(linfo, lock);
spin_unlock(&linfo->lock);
goto check_lock_state;
}
@@ -512,17 +512,13 @@ int scoutfs_lock_inode_index(struct super_block *sb, int mode,
void scoutfs_unlock(struct super_block *sb, struct scoutfs_lock *lock)
{
DECLARE_LOCK_INFO(sb, linfo);
unsigned int seconds = 60;
trace_scoutfs_unlock(sb, lock);
spin_lock(&linfo->lock);
lock->holders--;
if (lock->holders == 0) {
if (lock->flags & SCOUTFS_LOCK_BLOCKING)
seconds = 0;
queue_blocking_work(linfo, lock, seconds);
}
if (lock->holders == 0 && (lock->flags & SCOUTFS_LOCK_BLOCKING))
queue_blocking_work(linfo, lock);
spin_unlock(&linfo->lock);
put_scoutfs_lock(sb, lock);
@@ -556,7 +552,7 @@ out:
static void scoutfs_downconvert_func(struct work_struct *work)
{
struct scoutfs_lock *lock = container_of(work, struct scoutfs_lock,
dc_work.work);
dc_work);
struct super_block *sb = lock->sb;
DECLARE_LOCK_INFO(sb, linfo);
kmod/src/lock.h
+1 -1
View File
@@ -21,7 +21,7 @@ struct scoutfs_lock {
unsigned int refcnt;
unsigned int holders; /* Tracks active users of this lock */
unsigned int flags;
struct delayed_work dc_work;
struct work_struct dc_work;
};
int scoutfs_lock_ino_group(struct super_block *sb, int mode, u64 ino,