Re: [PATCH 14/17] staging: lustre: change sai_thread to sai_task.

From: Dilger, Andreas
Date: Thu Mar 08 2018 - 19:20:36 EST

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> On Mar 1, 2018, at 16:31, NeilBrown <neilb@xxxxxxxx> wrote:
>
> Rather than allocating a ptlrpc_thread for the
> stat-ahead thread, just use the task_struct provided
> by kthreads directly.
>
> As nothing ever waits for the sai_task, it must call do_exit()
> directly rather than simply return from the function.
> Also it cannot use kthread_should_stop() to know when to stop.
>
> There is one caller which can ask it to stop so we need a simple
> signaling mechanism. I've chosen to set ->sai_task to NULL
> when the thread should finish up. The thread notices this and
> cleans up and exits.
> lli_sa_lock is used to avoid races between waking up the process
> and the process exiting.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>

CC'd Fan Yong, who is the author for this code.

Reviewed-by: Andreas Dilger <andreas.dilger@xxxxxxxxx>

> ---
> .../staging/lustre/lustre/llite/llite_internal.h | 2
> drivers/staging/lustre/lustre/llite/statahead.c | 118 +++++++++-----------
> 2 files changed, 54 insertions(+), 66 deletions(-)
>
> diff --git a/drivers/staging/lustre/lustre/llite/llite_internal.h b/drivers/staging/lustre/lustre/llite/llite_internal.h
> index 0c2d717fd526..d46bcf71b273 100644
> --- a/drivers/staging/lustre/lustre/llite/llite_internal.h
> +++ b/drivers/staging/lustre/lustre/llite/llite_internal.h
> @@ -1070,7 +1070,7 @@ struct ll_statahead_info {
> sai_agl_valid:1,/* AGL is valid for the dir */
> sai_in_readpage:1;/* statahead in readdir() */
> wait_queue_head_t sai_waitq; /* stat-ahead wait queue */
> - struct ptlrpc_thread sai_thread; /* stat-ahead thread */
> + struct task_struct *sai_task; /* stat-ahead thread */
> struct task_struct *sai_agl_task; /* AGL thread */
> struct list_head sai_interim_entries; /* entries which got async
> * stat reply, but not
> diff --git a/drivers/staging/lustre/lustre/llite/statahead.c b/drivers/staging/lustre/lustre/llite/statahead.c
> index 39241b952bf4..155ce3cf6f60 100644
> --- a/drivers/staging/lustre/lustre/llite/statahead.c
> +++ b/drivers/staging/lustre/lustre/llite/statahead.c
> @@ -267,7 +267,7 @@ sa_kill(struct ll_statahead_info *sai, struct sa_entry *entry)
>
> /* called by scanner after use, sa_entry will be killed */
> static void
> -sa_put(struct ll_statahead_info *sai, struct sa_entry *entry)
> +sa_put(struct ll_statahead_info *sai, struct sa_entry *entry, struct ll_inode_info *lli)
> {
> struct sa_entry *tmp, *next;
>
> @@ -295,7 +295,11 @@ sa_put(struct ll_statahead_info *sai, struct sa_entry *entry)
> sa_kill(sai, tmp);
> }
>
> - wake_up(&sai->sai_thread.t_ctl_waitq);
> + spin_lock(&lli->lli_sa_lock);
> + if (sai->sai_task)
> + wake_up_process(sai->sai_task);
> + spin_unlock(&lli->lli_sa_lock);
> +
> }
>
> /*
> @@ -403,7 +407,6 @@ static struct ll_statahead_info *ll_sai_alloc(struct dentry *dentry)
> sai->sai_max = LL_SA_RPC_MIN;
> sai->sai_index = 1;
> init_waitqueue_head(&sai->sai_waitq);
> - init_waitqueue_head(&sai->sai_thread.t_ctl_waitq);
>
> INIT_LIST_HEAD(&sai->sai_interim_entries);
> INIT_LIST_HEAD(&sai->sai_entries);
> @@ -465,7 +468,7 @@ static void ll_sai_put(struct ll_statahead_info *sai)
> lli->lli_sai = NULL;
> spin_unlock(&lli->lli_sa_lock);
>
> - LASSERT(thread_is_stopped(&sai->sai_thread));
> + LASSERT(sai->sai_task == NULL);
> LASSERT(sai->sai_agl_task == NULL);
> LASSERT(sai->sai_sent == sai->sai_replied);
> LASSERT(!sa_has_callback(sai));
> @@ -646,7 +649,6 @@ static int ll_statahead_interpret(struct ptlrpc_request *req,
> struct ll_inode_info *lli = ll_i2info(dir);
> struct ll_statahead_info *sai = lli->lli_sai;
> struct sa_entry *entry = (struct sa_entry *)minfo->mi_cbdata;
> - wait_queue_head_t *waitq = NULL;
> __u64 handle = 0;
>
> if (it_disposition(it, DISP_LOOKUP_NEG))
> @@ -657,7 +659,6 @@ static int ll_statahead_interpret(struct ptlrpc_request *req,
> * sai should be always valid, no need to refcount
> */
> LASSERT(sai);
> - LASSERT(!thread_is_stopped(&sai->sai_thread));
> LASSERT(entry);
>
> CDEBUG(D_READA, "sa_entry %.*s rc %d\n",
> @@ -681,8 +682,9 @@ static int ll_statahead_interpret(struct ptlrpc_request *req,
> spin_lock(&lli->lli_sa_lock);
> if (rc) {
> if (__sa_make_ready(sai, entry, rc))
> - waitq = &sai->sai_waitq;
> + wake_up(&sai->sai_waitq);
> } else {
> + int first = 0;
> entry->se_minfo = minfo;
> entry->se_req = ptlrpc_request_addref(req);
> /*
> @@ -693,14 +695,15 @@ static int ll_statahead_interpret(struct ptlrpc_request *req,
> */
> entry->se_handle = handle;
> if (!sa_has_callback(sai))
> - waitq = &sai->sai_thread.t_ctl_waitq;
> + first = 1;
>
> list_add_tail(&entry->se_list, &sai->sai_interim_entries);
> +
> + if (first && sai->sai_task)
> + wake_up_process(sai->sai_task);
> }
> sai->sai_replied++;
>
> - if (waitq)
> - wake_up(waitq);
> spin_unlock(&lli->lli_sa_lock);
>
> return rc;
> @@ -942,17 +945,13 @@ static int ll_statahead_thread(void *arg)
> struct inode *dir = d_inode(parent);
> struct ll_inode_info *lli = ll_i2info(dir);
> struct ll_sb_info *sbi = ll_i2sbi(dir);
> - struct ll_statahead_info *sai;
> - struct ptlrpc_thread *sa_thread;
> + struct ll_statahead_info *sai = lli->lli_sai;
> struct page *page = NULL;
> __u64 pos = 0;
> int first = 0;
> int rc = 0;
> struct md_op_data *op_data;
>
> - sai = ll_sai_get(dir);
> - sa_thread = &sai->sai_thread;
> - sa_thread->t_pid = current_pid();
> CDEBUG(D_READA, "statahead thread starting: sai %p, parent %pd\n",
> sai, parent);
>
> @@ -965,21 +964,7 @@ static int ll_statahead_thread(void *arg)
>
> op_data->op_max_pages = ll_i2sbi(dir)->ll_md_brw_pages;
>
> - if (sbi->ll_flags & LL_SBI_AGL_ENABLED)
> - ll_start_agl(parent, sai);
> -
> - atomic_inc(&sbi->ll_sa_total);
> - spin_lock(&lli->lli_sa_lock);
> - if (thread_is_init(sa_thread))
> - /* If someone else has changed the thread state
> - * (e.g. already changed to SVC_STOPPING), we can't just
> - * blindly overwrite that setting.
> - */
> - thread_set_flags(sa_thread, SVC_RUNNING);
> - spin_unlock(&lli->lli_sa_lock);
> - wake_up(&sa_thread->t_ctl_waitq);
> -
> - while (pos != MDS_DIR_END_OFF && thread_is_running(sa_thread)) {
> + while (pos != MDS_DIR_END_OFF && sai->sai_task) {
> struct lu_dirpage *dp;
> struct lu_dirent *ent;
>
> @@ -996,7 +981,7 @@ static int ll_statahead_thread(void *arg)
>
> dp = page_address(page);
> for (ent = lu_dirent_start(dp);
> - ent && thread_is_running(sa_thread) && !sa_low_hit(sai);
> + ent && sai->sai_task && !sa_low_hit(sai);
> ent = lu_dirent_next(ent)) {
> struct lu_fid fid;
> __u64 hash;
> @@ -1046,13 +1031,7 @@ static int ll_statahead_thread(void *arg)
>
> fid_le_to_cpu(&fid, &ent->lde_fid);
>
> - /* wait for spare statahead window */
> do {
> - wait_event_idle(sa_thread->t_ctl_waitq,
> - !sa_sent_full(sai) ||
> - sa_has_callback(sai) ||
> - !list_empty(&sai->sai_agls) ||
> - !thread_is_running(sa_thread));
> sa_handle_callback(sai);
>
> spin_lock(&lli->lli_agl_lock);
> @@ -1072,8 +1051,16 @@ static int ll_statahead_thread(void *arg)
> spin_lock(&lli->lli_agl_lock);
> }
> spin_unlock(&lli->lli_agl_lock);
> - } while (sa_sent_full(sai) &&
> - thread_is_running(sa_thread));
> +
> + set_current_state(TASK_IDLE);
> + if (sa_sent_full(sai) &&
> + !sa_has_callback(sai) &&
> + agl_list_empty(sai) &&
> + sai->sai_task)
> + /* wait for spare statahead window */
> + schedule();
> + __set_current_state(TASK_RUNNING);
> + } while (sa_sent_full(sai) && sai->sai_task);
>
> sa_statahead(parent, name, namelen, &fid);
> }
> @@ -1096,7 +1083,7 @@ static int ll_statahead_thread(void *arg)
>
> if (rc < 0) {
> spin_lock(&lli->lli_sa_lock);
> - thread_set_flags(sa_thread, SVC_STOPPING);
> + sai->sai_task = NULL;
> lli->lli_sa_enabled = 0;
> spin_unlock(&lli->lli_sa_lock);
> }
> @@ -1105,12 +1092,14 @@ static int ll_statahead_thread(void *arg)
> * statahead is finished, but statahead entries need to be cached, wait
> * for file release to stop me.
> */
> - while (thread_is_running(sa_thread)) {
> - wait_event_idle(sa_thread->t_ctl_waitq,
> - sa_has_callback(sai) ||
> - !thread_is_running(sa_thread));
> -
> + while (sai->sai_task) {
> sa_handle_callback(sai);
> +
> + set_current_state(TASK_IDLE);
> + if (!sa_has_callback(sai) &&
> + sai->sai_task)
> + schedule();
> + __set_current_state(TASK_RUNNING);
> }
> out:
> if (sai->sai_agl_task) {
> @@ -1126,26 +1115,23 @@ static int ll_statahead_thread(void *arg)
> */
> while (sai->sai_sent != sai->sai_replied) {
> /* in case we're not woken up, timeout wait */
> - wait_event_idle_timeout(sa_thread->t_ctl_waitq,
> - sai->sai_sent == sai->sai_replied,
> - HZ>>3);
> + schedule_timeout_idle(HZ>>3);
> }
>
> /* release resources held by statahead RPCs */
> sa_handle_callback(sai);
>
> - spin_lock(&lli->lli_sa_lock);
> - thread_set_flags(sa_thread, SVC_STOPPED);
> - spin_unlock(&lli->lli_sa_lock);
> -
> CDEBUG(D_READA, "statahead thread stopped: sai %p, parent %pd\n",
> sai, parent);
>
> + spin_lock(&lli->lli_sa_lock);
> + sai->sai_task = NULL;
> + spin_unlock(&lli->lli_sa_lock);
> +
> wake_up(&sai->sai_waitq);
> - wake_up(&sa_thread->t_ctl_waitq);
> ll_sai_put(sai);
>
> - return rc;
> + do_exit(rc);
> }
>
> /* authorize opened dir handle @key to statahead */
> @@ -1187,13 +1173,13 @@ void ll_deauthorize_statahead(struct inode *dir, void *key)
> lli->lli_opendir_pid = 0;
> lli->lli_sa_enabled = 0;
> sai = lli->lli_sai;
> - if (sai && thread_is_running(&sai->sai_thread)) {
> + if (sai && sai->sai_task) {
> /*
> * statahead thread may not quit yet because it needs to cache
> * entries, now it's time to tell it to quit.
> */
> - thread_set_flags(&sai->sai_thread, SVC_STOPPING);
> - wake_up(&sai->sai_thread.t_ctl_waitq);
> + wake_up_process(sai->sai_task);
> + sai->sai_task = NULL;
> }
> spin_unlock(&lli->lli_sa_lock);
> }
> @@ -1463,7 +1449,7 @@ static int revalidate_statahead_dentry(struct inode *dir,
> */
> ldd = ll_d2d(*dentryp);
> ldd->lld_sa_generation = lli->lli_sa_generation;
> - sa_put(sai, entry);
> + sa_put(sai, entry, lli);
> return rc;
> }
>
> @@ -1483,7 +1469,6 @@ static int start_statahead_thread(struct inode *dir, struct dentry *dentry)
> {
> struct ll_inode_info *lli = ll_i2info(dir);
> struct ll_statahead_info *sai = NULL;
> - struct ptlrpc_thread *thread;
> struct task_struct *task;
> struct dentry *parent = dentry->d_parent;
> int rc;
> @@ -1523,18 +1508,21 @@ static int start_statahead_thread(struct inode *dir, struct dentry *dentry)
> CDEBUG(D_READA, "start statahead thread: [pid %d] [parent %pd]\n",
> current_pid(), parent);
>
> - task = kthread_run(ll_statahead_thread, parent, "ll_sa_%u",
> - lli->lli_opendir_pid);
> - thread = &sai->sai_thread;
> + task = kthread_create(ll_statahead_thread, parent, "ll_sa_%u",
> + lli->lli_opendir_pid);
> if (IS_ERR(task)) {
> rc = PTR_ERR(task);
> CERROR("can't start ll_sa thread, rc : %d\n", rc);
> goto out;
> }
>
> - wait_event_idle(thread->t_ctl_waitq,
> - thread_is_running(thread) || thread_is_stopped(thread));
> - ll_sai_put(sai);
> + if (ll_i2sbi(parent->d_inode)->ll_flags & LL_SBI_AGL_ENABLED)
> + ll_start_agl(parent, sai);
> +
> + atomic_inc(&ll_i2sbi(parent->d_inode)->ll_sa_total);
> + sai->sai_task = task;
> +
> + wake_up_process(task);
>
> /*
> * We don't stat-ahead for the first dirent since we are already in
>
>

Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation

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