X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=blobdiff_plain;f=lustre%2Fllite%2Fstatahead.c;h=27c41586b67e07dc09b2115cbbfedd3962e7bbe8;hp=c62b3ea0f379a257033cc8c088bf8793fe860104;hb=5db0e2de00f6b3d687fc4fe01f05a687fc74271c;hpb=83cce524dd47e5433dfdbe530f3b453807ef6976

diff --git a/lustre/llite/statahead.c b/lustre/llite/statahead.c
index c62b3ea..27c4158 100644
--- a/lustre/llite/statahead.c
+++ b/lustre/llite/statahead.c
@@ -27,7 +27,7 @@
  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  * Use is subject to license terms.
  *
- * Copyright (c) 2011, 2013, Intel Corporation.
+ * Copyright (c) 2011, 2015, Intel Corporation.
  */
 /*
  * This file is part of Lustre, http://www.lustre.org/
@@ -36,6 +36,7 @@
 
 #include <linux/fs.h>
 #include <linux/sched.h>
+#include <linux/kthread.h>
 #include <linux/mm.h>
 #include <linux/highmem.h>
 #include <linux/pagemap.h>
@@ -57,11 +58,11 @@ typedef enum {
 
 /* sa_entry is not refcounted: statahead thread allocates it and do async stat,
  * and in async stat callback ll_statahead_interpret() will add it into
- * sai_cb_entries, later statahead thread will call sa_handle_callback() to
+ * sai_interim_entries, later statahead thread will call sa_handle_callback() to
  * instantiate entry and move it into sai_entries, and then only scanner process
  * can access and free it. */
 struct sa_entry {
-	/* link into sai_cb_entries or sai_entries */
+	/* link into sai_interim_entries or sai_entries */
 	struct list_head	se_list;
 	/* link into sai hash table locally */
 	struct list_head	se_hash;
@@ -81,6 +82,8 @@ struct sa_entry {
 	struct inode	       *se_inode;
 	/* entry name */
 	struct qstr		se_qstr;
+	/* entry fid */
+	struct lu_fid		se_fid;
 };
 
 static unsigned int sai_generation = 0;
@@ -91,23 +94,20 @@ static inline int sa_unhashed(struct sa_entry *entry)
 	return list_empty(&entry->se_hash);
 }
 
-/*
- * The entry only can be released by the caller, it is necessary to hold lock.
- */
+/* sa_entry is ready to use */
 static inline int sa_ready(struct sa_entry *entry)
 {
 	smp_rmb();
 	return (entry->se_state != SA_ENTRY_INIT);
 }
 
+/* hash value to put in sai_cache */
 static inline int sa_hash(int val)
 {
 	return val & LL_SA_CACHE_MASK;
 }
 
-/*
- * Insert entry to hash SA table.
- */
+/* hash entry into sai_cache */
 static inline void
 sa_rehash(struct ll_statahead_info *sai, struct sa_entry *entry)
 {
@@ -118,9 +118,7 @@ sa_rehash(struct ll_statahead_info *sai, struct sa_entry *entry)
 	spin_unlock(&sai->sai_cache_lock[i]);
 }
 
-/*
- * Remove entry from SA table.
- */
+/* unhash entry from sai_cache */
 static inline void
 sa_unhash(struct ll_statahead_info *sai, struct sa_entry *entry)
 {
@@ -144,11 +142,13 @@ agl_first_entry(struct ll_statahead_info *sai)
 			  lli_agl_list);
 }
 
+/* statahead window is full */
 static inline int sa_sent_full(struct ll_statahead_info *sai)
 {
 	return atomic_read(&sai->sai_cache_count) >= sai->sai_max;
 }
 
+/* got async stat replies */
 static inline int sa_has_callback(struct ll_statahead_info *sai)
 {
 	return !list_empty(&sai->sai_interim_entries);
@@ -172,7 +172,7 @@ static inline int sa_low_hit(struct ll_statahead_info *sai)
 }
 
 /*
- * If the given index is behind of statahead window more than
+ * if the given index is behind of statahead window more than
  * SA_OMITTED_ENTRY_MAX, then it is old.
  */
 static inline int is_omitted_entry(struct ll_statahead_info *sai, __u64 index)
@@ -181,9 +181,10 @@ static inline int is_omitted_entry(struct ll_statahead_info *sai, __u64 index)
                  sai->sai_index);
 }
 
-/* allocate sa_entry and add it into hash to let scanner process to find it */
+/* allocate sa_entry and hash it to allow scanner process to find it */
 static struct sa_entry *
-sa_alloc(struct ll_statahead_info *sai, __u64 index, const char *name, int len)
+sa_alloc(struct ll_statahead_info *sai, __u64 index, const char *name, int len,
+	 const struct lu_fid *fid)
 {
 	struct ll_inode_info *lli;
 	struct sa_entry *entry;
@@ -209,8 +210,10 @@ sa_alloc(struct ll_statahead_info *sai, __u64 index, const char *name, int len)
 	entry->se_qstr.hash = full_name_hash(name, len);
 	entry->se_qstr.len = len;
 	entry->se_qstr.name = dname;
+	entry->se_fid = *fid;
+
+	lli = ll_i2info(sai->sai_dentry->d_inode);
 
-	lli = ll_i2info(sai->sai_inode);
 	spin_lock(&lli->lli_sa_lock);
 	INIT_LIST_HEAD(&entry->se_list);
 	sa_rehash(sai, entry);
@@ -221,7 +224,7 @@ sa_alloc(struct ll_statahead_info *sai, __u64 index, const char *name, int len)
 	RETURN(entry);
 }
 
-/* free sa_entry which should have been unhashed and not in any list */
+/* free sa_entry, which should have been unhashed and not in any list */
 static void sa_free(struct ll_statahead_info *sai, struct sa_entry *entry)
 {
 	CDEBUG(D_READA, "free sa entry %.*s(%p) index "LPU64"\n",
@@ -235,8 +238,9 @@ static void sa_free(struct ll_statahead_info *sai, struct sa_entry *entry)
 	atomic_dec(&sai->sai_cache_count);
 }
 
-/* find sa_entry by name, used by directory scanner, lock is not needed because
- * only scanner can remove the entry from hash.
+/*
+ * find sa_entry by name, used by directory scanner, lock is not needed because
+ * only scanner can remove the entry from cache.
  */
 static struct sa_entry *
 sa_get(struct ll_statahead_info *sai, const struct qstr *qstr)
@@ -253,10 +257,11 @@ sa_get(struct ll_statahead_info *sai, const struct qstr *qstr)
 	return NULL;
 }
 
+/* unhash and unlink sa_entry, and then free it */
 static inline void
 sa_kill(struct ll_statahead_info *sai, struct sa_entry *entry)
 {
-	struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
+	struct ll_inode_info *lli = ll_i2info(sai->sai_dentry->d_inode);
 
 	LASSERT(!sa_unhashed(entry));
 	LASSERT(!list_empty(&entry->se_list));
@@ -281,7 +286,7 @@ sa_put(struct ll_statahead_info *sai, struct sa_entry *entry)
 	struct sa_entry *tmp, *next;
 
 	if (entry != NULL && entry->se_state == SA_ENTRY_SUCC) {
-		struct ll_sb_info *sbi = ll_i2sbi(sai->sai_inode);
+		struct ll_sb_info *sbi = ll_i2sbi(sai->sai_dentry->d_inode);
 
 		sai->sai_hit++;
 		sai->sai_consecutive_miss = 0;
@@ -312,12 +317,11 @@ __sa_make_ready(struct ll_statahead_info *sai, struct sa_entry *entry, int ret)
 {
 	struct sa_entry *se;
 	struct list_head *pos = &sai->sai_entries;
+	__u64 index = entry->se_index;
 
 	LASSERT(!sa_ready(entry));
 	LASSERT(list_empty(&entry->se_list));
 
-	entry->se_state = ret < 0 ? SA_ENTRY_INVA : SA_ENTRY_SUCC;
-
 	list_for_each_entry_reverse(se, &sai->sai_entries, se_list) {
 		if (se->se_index < entry->se_index) {
 			pos = &se->se_list;
@@ -325,16 +329,19 @@ __sa_make_ready(struct ll_statahead_info *sai, struct sa_entry *entry, int ret)
 		}
 	}
 	list_add(&entry->se_list, pos);
+	entry->se_state = ret < 0 ? SA_ENTRY_INVA : SA_ENTRY_SUCC;
 
-	return (entry->se_index == sai->sai_index_wait);
+	return (index == sai->sai_index_wait);
 }
 
-/* release resources used in async stat RPC, complete entry information and
- * wakeup if necessary */
+/*
+ * release resources used in async stat RPC, update entry state and wakeup if
+ * scanner process it waiting on this entry.
+ */
 static void
 sa_make_ready(struct ll_statahead_info *sai, struct sa_entry *entry, int ret)
 {
-	struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
+	struct ll_inode_info *lli = ll_i2info(sai->sai_dentry->d_inode);
 	struct md_enqueue_info *minfo = entry->se_minfo;
 	struct ptlrpc_request *req = entry->se_req;
 	bool wakeup;
@@ -360,14 +367,12 @@ sa_make_ready(struct ll_statahead_info *sai, struct sa_entry *entry, int ret)
 		wake_up(&sai->sai_waitq);
 }
 
-/*
- * Insert inode into the list of sai_agls.
- */
+/* insert inode into the list of sai_agls */
 static void ll_agl_add(struct ll_statahead_info *sai,
                        struct inode *inode, int index)
 {
 	struct ll_inode_info *child  = ll_i2info(inode);
-	struct ll_inode_info *parent = ll_i2info(sai->sai_inode);
+	struct ll_inode_info *parent = ll_i2info(sai->sai_dentry->d_inode);
 	int                   added  = 0;
 
 	spin_lock(&child->lli_agl_lock);
@@ -391,24 +396,20 @@ static void ll_agl_add(struct ll_statahead_info *sai,
 		wake_up(&sai->sai_agl_thread.t_ctl_waitq);
 }
 
-static struct ll_statahead_info *ll_sai_alloc(void)
+/* allocate sai */
+static struct ll_statahead_info *ll_sai_alloc(struct dentry *dentry)
 {
 	struct ll_statahead_info *sai;
-	int                       i;
+	struct ll_inode_info *lli = ll_i2info(dentry->d_inode);
+	int i;
 	ENTRY;
 
 	OBD_ALLOC_PTR(sai);
 	if (!sai)
 		RETURN(NULL);
 
+	sai->sai_dentry = dget(dentry);
 	atomic_set(&sai->sai_refcount, 1);
-
-	spin_lock(&sai_generation_lock);
-	sai->sai_generation = ++sai_generation;
-	if (unlikely(sai_generation == 0))
-		sai->sai_generation = ++sai_generation;
-	spin_unlock(&sai_generation_lock);
-
 	sai->sai_max = LL_SA_RPC_MIN;
 	sai->sai_index = 1;
 	init_waitqueue_head(&sai->sai_waitq);
@@ -425,9 +426,27 @@ static struct ll_statahead_info *ll_sai_alloc(void)
 	}
 	atomic_set(&sai->sai_cache_count, 0);
 
+	spin_lock(&sai_generation_lock);
+	lli->lli_sa_generation = ++sai_generation;
+	if (unlikely(sai_generation == 0))
+		lli->lli_sa_generation = ++sai_generation;
+	spin_unlock(&sai_generation_lock);
+
 	RETURN(sai);
 }
 
+/* free sai */
+static inline void ll_sai_free(struct ll_statahead_info *sai)
+{
+	LASSERT(sai->sai_dentry != NULL);
+	dput(sai->sai_dentry);
+	OBD_FREE_PTR(sai);
+}
+
+/*
+ * take refcount of sai if sai for @dir exists, which means statahead is on for
+ * this directory.
+ */
 static inline struct ll_statahead_info *ll_sai_get(struct inode *dir)
 {
 	struct ll_inode_info *lli = ll_i2info(dir);
@@ -442,13 +461,17 @@ static inline struct ll_statahead_info *ll_sai_get(struct inode *dir)
 	return sai;
 }
 
+/*
+ * put sai refcount after use, if refcount reaches zero, free sai and sa_entries
+ * attached to it.
+ */
 static void ll_sai_put(struct ll_statahead_info *sai)
 {
-	struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
+	struct ll_inode_info *lli = ll_i2info(sai->sai_dentry->d_inode);
 
 	if (atomic_dec_and_lock(&sai->sai_refcount, &lli->lli_sa_lock)) {
 		struct sa_entry *entry, *next;
-		struct ll_sb_info *sbi = ll_i2sbi(sai->sai_inode);
+		struct ll_sb_info *sbi = ll_i2sbi(sai->sai_dentry->d_inode);
 
 		lli->lli_sai = NULL;
 		spin_unlock(&lli->lli_sa_lock);
@@ -465,8 +488,7 @@ static void ll_sai_put(struct ll_statahead_info *sai)
 		LASSERT(atomic_read(&sai->sai_cache_count) == 0);
 		LASSERT(agl_list_empty(sai));
 
-		iput(sai->sai_inode);
-		OBD_FREE_PTR(sai);
+		ll_sai_free(sai);
 		atomic_dec(&sbi->ll_sa_running);
 	}
 }
@@ -534,12 +556,14 @@ static void ll_agl_trigger(struct inode *inode, struct ll_statahead_info *sai)
         EXIT;
 }
 
-/* prepare inode for sa entry, add it into agl list, now sa_entry is ready
- * to be used by scanner process. */
+/*
+ * prepare inode for sa entry, add it into agl list, now sa_entry is ready
+ * to be used by scanner process.
+ */
 static void sa_instantiate(struct ll_statahead_info *sai,
 				 struct sa_entry *entry)
 {
-	struct inode *dir = sai->sai_inode;
+	struct inode *dir = sai->sai_dentry->d_inode;
 	struct inode *child;
 	struct md_enqueue_info *minfo;
 	struct lookup_intent *it;
@@ -557,31 +581,18 @@ static void sa_instantiate(struct ll_statahead_info *sai,
         if (body == NULL)
                 GOTO(out, rc = -EFAULT);
 
-        child = entry->se_inode;
-        if (child == NULL) {
-                /*
-                 * lookup.
-                 */
-                LASSERT(fid_is_zero(&minfo->mi_data.op_fid2));
-
-                /* XXX: No fid in reply, this is probaly cross-ref case.
-                 * SA can't handle it yet. */
-		if (body->mbo_valid & OBD_MD_MDS)
-			GOTO(out, rc = -EAGAIN);
-	} else {
-		/*
-		 * revalidate.
-		 */
-		/* unlinked and re-created with the same name */
+	child = entry->se_inode;
+	if (child != NULL) {
+		/* revalidate; unlinked and re-created with the same name */
 		if (unlikely(!lu_fid_eq(&minfo->mi_data.op_fid2,
 					&body->mbo_fid1))) {
-                        entry->se_inode = NULL;
-                        iput(child);
-                        child = NULL;
-                }
-        }
+			entry->se_inode = NULL;
+			iput(child);
+			child = NULL;
+		}
+	}
 
-        it->d.lustre.it_lock_handle = entry->se_handle;
+	it->it_lock_handle = entry->se_handle;
 	rc = md_revalidate_lock(ll_i2mdexp(dir), it, ll_inode2fid(dir), NULL);
         if (rc != 1)
                 GOTO(out, rc = -EAGAIN);
@@ -610,12 +621,12 @@ out:
 	sa_make_ready(sai, entry, rc);
 }
 
-/* once there are async stat replies, instantiate sa_entry */
+/* once there are async stat replies, instantiate sa_entry from replies */
 static void sa_handle_callback(struct ll_statahead_info *sai)
 {
 	struct ll_inode_info *lli;
 
-	lli = ll_i2info(sai->sai_inode);
+	lli = ll_i2info(sai->sai_dentry->d_inode);
 
 	while (sa_has_callback(sai)) {
 		struct sa_entry *entry;
@@ -632,25 +643,13 @@ static void sa_handle_callback(struct ll_statahead_info *sai)
 
 		sa_instantiate(sai, entry);
 	}
-
-	spin_lock(&lli->lli_agl_lock);
-	while (!agl_list_empty(sai)) {
-		struct ll_inode_info *clli;
-
-		clli = agl_first_entry(sai);
-		list_del_init(&clli->lli_agl_list);
-		spin_unlock(&lli->lli_agl_lock);
-
-		ll_agl_trigger(&clli->lli_vfs_inode, sai);
-
-		spin_lock(&lli->lli_agl_lock);
-	}
-	spin_unlock(&lli->lli_agl_lock);
 }
 
-/* callback for async stat, because this is called in ptlrpcd context, we only
- * put sa_entry in sai_cb_entries list, and let sa_handle_callback() to really
- * prepare inode and instantiate sa_entry later. */
+/*
+ * callback for async stat RPC, because this is called in ptlrpcd context, we
+ * only put sa_entry in sai_interim_entries, and wake up statahead thread to
+ * really prepare inode and instantiate sa_entry later.
+ */
 static int ll_statahead_interpret(struct ptlrpc_request *req,
 				  struct md_enqueue_info *minfo, int rc)
 {
@@ -660,7 +659,7 @@ static int ll_statahead_interpret(struct ptlrpc_request *req,
 	struct ll_statahead_info *sai = lli->lli_sai;
 	struct sa_entry *entry = (struct sa_entry *)minfo->mi_cbdata;
 	__u64 handle = 0;
-	bool wakeup;
+	wait_queue_head_t *waitq = NULL;
 	ENTRY;
 
 	if (it_disposition(it, DISP_LOOKUP_NEG))
@@ -684,13 +683,14 @@ static int ll_statahead_interpret(struct ptlrpc_request *req,
 		 * thread enqueues lock on parent in readdir and another
 		 * process enqueues lock on child with parent lock held, eg.
 		 * unlink. */
-		handle = it->d.lustre.it_lock_handle;
+		handle = it->it_lock_handle;
 		ll_intent_drop_lock(it);
 	}
 
 	spin_lock(&lli->lli_sa_lock);
 	if (rc != 0) {
-		wakeup = __sa_make_ready(sai, entry, rc);
+		if (__sa_make_ready(sai, entry, rc))
+			waitq = &sai->sai_waitq;
 	} else {
 		entry->se_minfo = minfo;
 		entry->se_req = ptlrpc_request_addref(req);
@@ -699,123 +699,98 @@ static int ll_statahead_interpret(struct ptlrpc_request *req,
 		 * for readpage and other tries to enqueue lock on child
 		 * with parent's lock held, for example: unlink. */
 		entry->se_handle = handle;
-		wakeup = !sa_has_callback(sai);
+		if (!sa_has_callback(sai))
+			waitq = &sai->sai_thread.t_ctl_waitq;
+
 		list_add_tail(&entry->se_list, &sai->sai_interim_entries);
 	}
 	sai->sai_replied++;
-	if (wakeup)
-		wake_up(&sai->sai_thread.t_ctl_waitq);
+	if (waitq != NULL)
+		wake_up(waitq);
 	spin_unlock(&lli->lli_sa_lock);
 
 	RETURN(rc);
 }
 
-static void sa_fini_data(struct md_enqueue_info *minfo,
-                         struct ldlm_enqueue_info *einfo)
+/* finish async stat RPC arguments */
+static void sa_fini_data(struct md_enqueue_info *minfo)
 {
-        LASSERT(minfo && einfo);
         iput(minfo->mi_dir);
-        capa_put(minfo->mi_data.op_capa1);
-        capa_put(minfo->mi_data.op_capa2);
         OBD_FREE_PTR(minfo);
-        OBD_FREE_PTR(einfo);
 }
 
-/**
- * There is race condition between "capa_put" and "ll_statahead_interpret" for
- * accessing "op_data.op_capa[1,2]" as following:
- * "capa_put" releases "op_data.op_capa[1,2]"'s reference count after calling
- * "md_intent_getattr_async". But "ll_statahead_interpret" maybe run first, and
- * fill "op_data.op_capa[1,2]" as POISON, then cause "capa_put" access invalid
- * "ocapa". So here reserve "op_data.op_capa[1,2]" in "pcapa" before calling
- * "md_intent_getattr_async".
+/*
+ * prepare arguments for async stat RPC.
  */
-static int sa_prep_data(struct inode *dir, struct inode *child,
-			struct sa_entry *entry, struct md_enqueue_info **pmi,
-			struct ldlm_enqueue_info **pei,
-			struct obd_capa **pcapa)
+static struct md_enqueue_info *
+sa_prep_data(struct inode *dir, struct inode *child, struct sa_entry *entry)
 {
-        struct qstr              *qstr = &entry->se_qstr;
-        struct md_enqueue_info   *minfo;
-        struct ldlm_enqueue_info *einfo;
-        struct md_op_data        *op_data;
-
-        OBD_ALLOC_PTR(einfo);
-        if (einfo == NULL)
-                return -ENOMEM;
-
-        OBD_ALLOC_PTR(minfo);
-        if (minfo == NULL) {
-                OBD_FREE_PTR(einfo);
-                return -ENOMEM;
-        }
+	struct md_enqueue_info   *minfo;
+	struct ldlm_enqueue_info *einfo;
+	struct md_op_data        *op_data;
 
-        op_data = ll_prep_md_op_data(&minfo->mi_data, dir, child, qstr->name,
-                                     qstr->len, 0, LUSTRE_OPC_ANY, NULL);
-        if (IS_ERR(op_data)) {
-                OBD_FREE_PTR(einfo);
-                OBD_FREE_PTR(minfo);
-                return PTR_ERR(op_data);
-        }
+	OBD_ALLOC_PTR(minfo);
+	if (minfo == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	op_data = ll_prep_md_op_data(&minfo->mi_data, dir, child, NULL, 0, 0,
+				     LUSTRE_OPC_ANY, NULL);
+	if (IS_ERR(op_data)) {
+		OBD_FREE_PTR(minfo);
+		return (struct md_enqueue_info *)op_data;
+	}
+
+	if (child == NULL)
+		op_data->op_fid2 = entry->se_fid;
 
 	minfo->mi_it.it_op = IT_GETATTR;
 	minfo->mi_dir = igrab(dir);
 	minfo->mi_cb = ll_statahead_interpret;
 	minfo->mi_cbdata = entry;
 
-        einfo->ei_type   = LDLM_IBITS;
-        einfo->ei_mode   = it_to_lock_mode(&minfo->mi_it);
-        einfo->ei_cb_bl  = ll_md_blocking_ast;
-        einfo->ei_cb_cp  = ldlm_completion_ast;
-        einfo->ei_cb_gl  = NULL;
-        einfo->ei_cbdata = NULL;
-
-        *pmi = minfo;
-        *pei = einfo;
-        pcapa[0] = op_data->op_capa1;
-        pcapa[1] = op_data->op_capa2;
+	einfo = &minfo->mi_einfo;
+	einfo->ei_type   = LDLM_IBITS;
+	einfo->ei_mode   = it_to_lock_mode(&minfo->mi_it);
+	einfo->ei_cb_bl  = ll_md_blocking_ast;
+	einfo->ei_cb_cp  = ldlm_completion_ast;
+	einfo->ei_cb_gl  = NULL;
+	einfo->ei_cbdata = NULL;
 
-        return 0;
+	return minfo;
 }
 
+/* async stat for file not found in dcache */
 static int sa_lookup(struct inode *dir, struct sa_entry *entry)
 {
 	struct md_enqueue_info   *minfo;
-	struct ldlm_enqueue_info *einfo;
-	struct obd_capa          *capas[2];
 	int                       rc;
 	ENTRY;
 
-	rc = sa_prep_data(dir, NULL, entry, &minfo, &einfo, capas);
-	if (rc)
-		RETURN(rc);
+	minfo = sa_prep_data(dir, NULL, entry);
+	if (IS_ERR(minfo))
+		RETURN(PTR_ERR(minfo));
 
-	rc = md_intent_getattr_async(ll_i2mdexp(dir), minfo, einfo);
-	if (!rc) {
-		capa_put(capas[0]);
-		capa_put(capas[1]);
-	} else {
-		sa_fini_data(minfo, einfo);
-	}
+	rc = md_intent_getattr_async(ll_i2mdexp(dir), minfo);
+	if (rc < 0)
+		sa_fini_data(minfo);
 
 	RETURN(rc);
 }
 
 /**
- * similar to ll_revalidate_it().
- * \retval      1 -- dentry valid
- * \retval      0 -- will send stat-ahead request
- * \retval others -- prepare stat-ahead request failed
+ * async stat for file found in dcache, similar to .revalidate
+ *
+ * \retval	1 dentry valid, no RPC sent
+ * \retval	0 dentry invalid, will send async stat RPC
+ * \retval	negative number upon error
  */
 static int sa_revalidate(struct inode *dir, struct sa_entry *entry,
 			 struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
 	struct lookup_intent it = { .it_op = IT_GETATTR,
-				    .d.lustre.it_lock_handle = 0 };
+				    .it_lock_handle = 0 };
 	struct md_enqueue_info *minfo;
-	struct ldlm_enqueue_info *einfo;
-	struct obd_capa *capas[2];
 	int rc;
 	ENTRY;
 
@@ -829,32 +804,31 @@ static int sa_revalidate(struct inode *dir, struct sa_entry *entry,
 	rc = md_revalidate_lock(ll_i2mdexp(dir), &it, ll_inode2fid(inode),
 				NULL);
 	if (rc == 1) {
-		entry->se_handle = it.d.lustre.it_lock_handle;
+		entry->se_handle = it.it_lock_handle;
 		ll_intent_release(&it);
 		RETURN(1);
 	}
 
-	rc = sa_prep_data(dir, inode, entry, &minfo, &einfo, capas);
-	if (rc) {
+	minfo = sa_prep_data(dir, inode, entry);
+	if (IS_ERR(minfo)) {
 		entry->se_inode = NULL;
 		iput(inode);
-		RETURN(rc);
+		RETURN(PTR_ERR(minfo));
 	}
 
-	rc = md_intent_getattr_async(ll_i2mdexp(dir), minfo, einfo);
-	if (!rc) {
-		capa_put(capas[0]);
-		capa_put(capas[1]);
-	} else {
+	rc = md_intent_getattr_async(ll_i2mdexp(dir), minfo);
+	if (rc < 0) {
 		entry->se_inode = NULL;
 		iput(inode);
-		sa_fini_data(minfo, einfo);
+		sa_fini_data(minfo);
 	}
 
 	RETURN(rc);
 }
 
-static void sa_statahead(struct dentry *parent, const char *name, int len)
+/* async stat for file with @name */
+static void sa_statahead(struct dentry *parent, const char *name, int len,
+			 const struct lu_fid *fid)
 {
 	struct inode *dir = parent->d_inode;
 	struct ll_inode_info *lli = ll_i2info(dir);
@@ -864,7 +838,7 @@ static void sa_statahead(struct dentry *parent, const char *name, int len)
 	int rc;
 	ENTRY;
 
-	entry = sa_alloc(sai, sai->sai_index, name, len);
+	entry = sa_alloc(sai, sai->sai_index, name, len, fid);
 	if (IS_ERR(entry))
 		RETURN_EXIT;
 
@@ -890,6 +864,7 @@ static void sa_statahead(struct dentry *parent, const char *name, int len)
 	EXIT;
 }
 
+/* async glimpse (agl) thread main function */
 static int ll_agl_thread(void *arg)
 {
 	struct dentry *parent = (struct dentry *)arg;
@@ -961,6 +936,7 @@ static int ll_agl_thread(void *arg)
 	RETURN(0);
 }
 
+/* start agl thread */
 static void ll_start_agl(struct dentry *parent, struct ll_statahead_info *sai)
 {
 	struct ptlrpc_thread *thread = &sai->sai_agl_thread;
@@ -987,6 +963,7 @@ static void ll_start_agl(struct dentry *parent, struct ll_statahead_info *sai)
 	EXIT;
 }
 
+/* statahead thread main function */
 static int ll_statahead_thread(void *arg)
 {
 	struct dentry *parent = (struct dentry *)arg;
@@ -994,7 +971,7 @@ static int ll_statahead_thread(void *arg)
 	struct ll_inode_info *lli = ll_i2info(dir);
 	struct ll_sb_info *sbi = ll_i2sbi(dir);
 	struct ll_statahead_info *sai;
-	struct ptlrpc_thread *thread;
+	struct ptlrpc_thread *sa_thread;
 	struct ptlrpc_thread *agl_thread;
 	int first = 0;
 	struct md_op_data *op_data;
@@ -1006,9 +983,9 @@ static int ll_statahead_thread(void *arg)
 	ENTRY;
 
 	sai = ll_sai_get(dir);
-	thread = &sai->sai_thread;
+	sa_thread = &sai->sai_thread;
 	agl_thread = &sai->sai_agl_thread;
-	thread->t_pid = current_pid();
+	sa_thread->t_pid = current_pid();
 	CDEBUG(D_READA, "statahead thread starting: sai %p, parent %.*s\n",
 	       sai, parent->d_name.len, parent->d_name.name);
 
@@ -1024,16 +1001,16 @@ static int ll_statahead_thread(void *arg)
 
 	atomic_inc(&sbi->ll_sa_total);
 	spin_lock(&lli->lli_sa_lock);
-	if (thread_is_init(thread))
+	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(thread, SVC_RUNNING);
+		thread_set_flags(sa_thread, SVC_RUNNING);
 	spin_unlock(&lli->lli_sa_lock);
-	wake_up(&thread->t_ctl_waitq);
+	wake_up(&sa_thread->t_ctl_waitq);
 
 	ll_dir_chain_init(&chain);
-	while (pos != MDS_DIR_END_OFF && thread_is_running(thread)) {
+	while (pos != MDS_DIR_END_OFF && thread_is_running(sa_thread)) {
 		struct lu_dirpage *dp;
 		struct lu_dirent  *ent;
 
@@ -1051,12 +1028,13 @@ static int ll_statahead_thread(void *arg)
 
 		dp = page_address(page);
 		for (ent = lu_dirent_start(dp);
-		     ent != NULL && thread_is_running(thread) &&
+		     ent != NULL && thread_is_running(sa_thread) &&
 		     !sa_low_hit(sai);
 		     ent = lu_dirent_next(ent)) {
 			__u64 hash;
 			int namelen;
 			char *name;
+			struct lu_fid fid;
 
 			hash = le64_to_cpu(ent->lde_hash);
 			if (unlikely(hash < pos))
@@ -1099,20 +1077,38 @@ static int ll_statahead_thread(void *arg)
 			if (unlikely(++first == 1))
 				continue;
 
+			fid_le_to_cpu(&fid, &ent->lde_fid);
+
 			/* wait for spare statahead window */
 			do {
-				l_wait_event(thread->t_ctl_waitq,
+				l_wait_event(sa_thread->t_ctl_waitq,
 					     !sa_sent_full(sai) ||
 					     sa_has_callback(sai) ||
 					     !agl_list_empty(sai) ||
-					     !thread_is_running(thread),
+					     !thread_is_running(sa_thread),
 					     &lwi);
 
 				sa_handle_callback(sai);
+
+				spin_lock(&lli->lli_agl_lock);
+				while (sa_sent_full(sai) &&
+				       !agl_list_empty(sai)) {
+					struct ll_inode_info *clli;
+
+					clli = agl_first_entry(sai);
+					list_del_init(&clli->lli_agl_list);
+					spin_unlock(&lli->lli_agl_lock);
+
+					ll_agl_trigger(&clli->lli_vfs_inode,
+							sai);
+
+					spin_lock(&lli->lli_agl_lock);
+				}
+				spin_unlock(&lli->lli_agl_lock);
 			} while (sa_sent_full(sai) &&
-				 thread_is_running(thread));
+				 thread_is_running(sa_thread));
 
-			sa_statahead(parent, name, namelen);
+			sa_statahead(parent, name, namelen, &fid);
 		}
 
 		pos = le64_to_cpu(dp->ldp_hash_end);
@@ -1137,18 +1133,17 @@ static int ll_statahead_thread(void *arg)
 
 	if (rc < 0) {
 		spin_lock(&lli->lli_sa_lock);
-		thread_set_flags(thread, SVC_STOPPING);
+		thread_set_flags(sa_thread, SVC_STOPPING);
 		lli->lli_sa_enabled = 0;
 		spin_unlock(&lli->lli_sa_lock);
 	}
 
 	/* statahead is finished, but statahead entries need to be cached, wait
 	 * for file release to stop me. */
-	while (thread_is_running(thread)) {
-		l_wait_event(thread->t_ctl_waitq,
+	while (thread_is_running(sa_thread)) {
+		l_wait_event(sa_thread->t_ctl_waitq,
 			     sa_has_callback(sai) ||
-			     !agl_list_empty(sai) ||
-			     !thread_is_running(thread),
+			     !thread_is_running(sa_thread),
 			     &lwi);
 
 		sa_handle_callback(sai);
@@ -1176,8 +1171,9 @@ out:
 	 * safely because statahead RPC will access sai data */
 	while (sai->sai_sent != sai->sai_replied) {
 		/* in case we're not woken up, timeout wait */
-		lwi = LWI_TIMEOUT(HZ >> 3, NULL, NULL);
-		l_wait_event(thread->t_ctl_waitq,
+		lwi = LWI_TIMEOUT(msecs_to_jiffies(MSEC_PER_SEC >> 3),
+				  NULL, NULL);
+		l_wait_event(sa_thread->t_ctl_waitq,
 			sai->sai_sent == sai->sai_replied, &lwi);
 	}
 
@@ -1185,19 +1181,20 @@ out:
 	sa_handle_callback(sai);
 
 	spin_lock(&lli->lli_sa_lock);
-	thread_set_flags(thread, SVC_STOPPED);
+	thread_set_flags(sa_thread, SVC_STOPPED);
 	spin_unlock(&lli->lli_sa_lock);
 
-	wake_up(&sai->sai_waitq);
-	wake_up(&thread->t_ctl_waitq);
-        ll_sai_put(sai);
 	CDEBUG(D_READA, "statahead thread stopped: sai %p, parent %.*s\n",
 	       sai, parent->d_name.len, parent->d_name.name);
-	dput(parent);
+
+	wake_up(&sai->sai_waitq);
+	wake_up(&sa_thread->t_ctl_waitq);
+	ll_sai_put(sai);
+
 	return rc;
 }
 
-/* authorize opened dir handle @key to statahead later */
+/* authorize opened dir handle @key to statahead */
 void ll_authorize_statahead(struct inode *dir, void *key)
 {
 	struct ll_inode_info *lli = ll_i2info(dir);
@@ -1216,8 +1213,10 @@ void ll_authorize_statahead(struct inode *dir, void *key)
 	spin_unlock(&lli->lli_sa_lock);
 }
 
-/* deauthorize opened dir handle @key to statahead, but statahead thread may
- * still be running, notify it to quit. */
+/*
+ * deauthorize opened dir handle @key to statahead, and notify statahead thread
+ * to quit if it's running.
+ */
 void ll_deauthorize_statahead(struct inode *dir, void *key)
 {
 	struct ll_inode_info *lli = ll_i2info(dir);
@@ -1246,20 +1245,21 @@ void ll_deauthorize_statahead(struct inode *dir, void *key)
 }
 
 enum {
-        /**
-         * not first dirent, or is "."
-         */
-        LS_NONE_FIRST_DE = 0,
-        /**
-         * the first non-hidden dirent
-         */
-        LS_FIRST_DE,
-        /**
-         * the first hidden dirent, that is "."
-         */
-        LS_FIRST_DOT_DE
+	/**
+	 * not first dirent, or is "."
+	 */
+	LS_NOT_FIRST_DE = 0,
+	/**
+	 * the first non-hidden dirent
+	 */
+	LS_FIRST_DE,
+	/**
+	 * the first hidden dirent, that is "."
+	 */
+	LS_FIRST_DOT_DE
 };
 
+/* file is first dirent under @dir */
 static int is_first_dirent(struct inode *dir, struct dentry *dentry)
 {
 	struct ll_dir_chain   chain;
@@ -1267,7 +1267,7 @@ static int is_first_dirent(struct inode *dir, struct dentry *dentry)
 	struct md_op_data    *op_data;
 	int                   dot_de;
 	struct page	     *page = NULL;
-	int                   rc     = LS_NONE_FIRST_DE;
+	int                   rc = LS_NOT_FIRST_DE;
 	__u64		      pos = 0;
 	ENTRY;
 
@@ -1346,7 +1346,7 @@ static int is_first_dirent(struct inode *dir, struct dentry *dentry)
 
 			if (target->len != namelen ||
 			    memcmp(target->name, name, namelen) != 0)
-				rc = LS_NONE_FIRST_DE;
+				rc = LS_NOT_FIRST_DE;
 			else if (!dot_de)
 				rc = LS_FIRST_DE;
 			else
@@ -1379,13 +1379,27 @@ out:
         return rc;
 }
 
+/**
+ * revalidate @dentryp from statahead cache
+ *
+ * \param[in] dir	parent directory
+ * \param[in] sai	sai structure
+ * \param[out] dentryp	pointer to dentry which will be revalidated
+ * \param[in] unplug	unplug statahead window only (normally for negative
+ *			dentry)
+ * \retval		1 on success, dentry is saved in @dentryp
+ * \retval		0 if revalidation failed (no proper lock on client)
+ * \retval		negative number upon error
+ */
 static int revalidate_statahead_dentry(struct inode *dir,
 					struct ll_statahead_info *sai,
 					struct dentry **dentryp,
-					int only_unplug)
+					bool unplug)
 {
 	struct sa_entry *entry = NULL;
 	struct l_wait_info lwi = { 0 };
+	struct ll_dentry_data *ldd;
+	struct ll_inode_info *lli = ll_i2info(dir);
 	int rc = 0;
 	ENTRY;
 
@@ -1416,34 +1430,38 @@ static int revalidate_statahead_dentry(struct inode *dir,
 		}
 	}
 
+	if (unplug)
+		GOTO(out, rc = 1);
+
 	entry = sa_get(sai, &(*dentryp)->d_name);
-	if (entry == NULL || only_unplug) {
-		sa_put(sai, entry);
-		RETURN(entry ? 1 : -EAGAIN);
-	}
+	if (entry == NULL)
+		GOTO(out, rc = -EAGAIN);
 
 	/* if statahead is busy in readdir, help it do post-work */
 	if (!sa_ready(entry) && sai->sai_in_readpage)
 		sa_handle_callback(sai);
 
 	if (!sa_ready(entry)) {
+		spin_lock(&lli->lli_sa_lock);
 		sai->sai_index_wait = entry->se_index;
+		spin_unlock(&lli->lli_sa_lock);
 		lwi = LWI_TIMEOUT_INTR(cfs_time_seconds(30), NULL,
-					LWI_ON_SIGNAL_NOOP, NULL);
-		rc = l_wait_event(sai->sai_waitq,
-				sa_ready(entry) ||
-				thread_is_stopped(&sai->sai_thread),
-				&lwi);
+				       LWI_ON_SIGNAL_NOOP, NULL);
+		rc = l_wait_event(sai->sai_waitq, sa_ready(entry), &lwi);
 		if (rc < 0) {
-			sa_put(sai, entry);
-			RETURN(-EAGAIN);
+			/*
+			 * entry may not be ready, so it may be used by inflight
+			 * statahead RPC, don't free it.
+			 */
+			entry = NULL;
+			GOTO(out, rc = -EAGAIN);
 		}
 	}
 
 	if (entry->se_state == SA_ENTRY_SUCC && entry->se_inode != NULL) {
 		struct inode *inode = entry->se_inode;
 		struct lookup_intent it = { .it_op = IT_GETATTR,
-					    .d.lustre.it_lock_handle =
+					    .it_lock_handle =
 						entry->se_handle };
 		__u64 bits;
 
@@ -1455,10 +1473,13 @@ static int revalidate_statahead_dentry(struct inode *dir,
 
 				alias = ll_splice_alias(inode, *dentryp);
 				if (IS_ERR(alias)) {
-					sa_put(sai, entry);
-					RETURN(PTR_ERR(alias));
+					ll_intent_release(&it);
+					GOTO(out, rc = PTR_ERR(alias));
 				}
 				*dentryp = alias;
+				/* statahead prepared this inode, transfer inode
+				 * refcount from sa_entry to dentry */
+				entry->se_inode = NULL;
 			} else if ((*dentryp)->d_inode != inode) {
 				/* revalidate, but inode is recreated */
 				CDEBUG(D_READA,
@@ -1471,12 +1492,9 @@ static int revalidate_statahead_dentry(struct inode *dir,
 					(*dentryp)->d_name.name,
 					PFID(ll_inode2fid((*dentryp)->d_inode)),
 					PFID(ll_inode2fid(inode)));
-				sa_put(sai, entry);
-				RETURN(-ESTALE);
-			} else {
-				iput(inode);
+				ll_intent_release(&it);
+				GOTO(out, rc = -ESTALE);
 			}
-			entry->se_inode = NULL;
 
 			if ((bits & MDS_INODELOCK_LOOKUP) &&
 			    d_lustre_invalid(*dentryp))
@@ -1484,16 +1502,40 @@ static int revalidate_statahead_dentry(struct inode *dir,
 			ll_intent_release(&it);
 		}
 	}
-
+out:
+	/*
+	 * statahead cached sa_entry can be used only once, and will be killed
+	 * right after use, so if lookup/revalidate accessed statahead cache,
+	 * set dentry ldd_sa_generation to parent lli_sa_generation, later if we
+	 * stat this file again, we know we've done statahead before, see
+	 * dentry_may_statahead().
+	 */
+	ldd = ll_d2d(*dentryp);
+	/* ldd can be NULL if llite lookup failed. */
+	if (ldd != NULL)
+		ldd->lld_sa_generation = lli->lli_sa_generation;
 	sa_put(sai, entry);
+
 	RETURN(rc);
 }
 
+/**
+ * start statahead thread
+ *
+ * \param[in] dir	parent directory
+ * \param[in] dentry	dentry that triggers statahead, normally the first
+ *			dirent under @dir
+ * \retval		-EAGAIN on success, because when this function is
+ *			called, it's already in lookup call, so client should
+ *			do it itself instead of waiting for statahead thread
+ *			to do it asynchronously.
+ * \retval		negative number upon error
+ */
 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 dentry *parent;
+	struct dentry *parent = dentry->d_parent;
 	struct ptlrpc_thread *thread;
 	struct l_wait_info lwi = { 0 };
 	struct task_struct *task;
@@ -1502,72 +1544,41 @@ static int start_statahead_thread(struct inode *dir, struct dentry *dentry)
 
 	/* I am the "lli_opendir_pid" owner, only me can set "lli_sai". */
 	rc = is_first_dirent(dir, dentry);
-	if (rc == LS_NONE_FIRST_DE)
+	if (rc == LS_NOT_FIRST_DE)
 		/* It is not "ls -{a}l" operation, no need statahead for it. */
-		GOTO(out, rc = -EAGAIN);
+		GOTO(out, rc = -EFAULT);
 
-	sai = ll_sai_alloc();
+	sai = ll_sai_alloc(parent);
 	if (sai == NULL)
 		GOTO(out, rc = -ENOMEM);
 
 	sai->sai_ls_all = (rc == LS_FIRST_DOT_DE);
-	sai->sai_inode = igrab(dir);
-	if (unlikely(sai->sai_inode == NULL)) {
-		CWARN("Do not start stat ahead on dying inode "DFID"\n",
-			PFID(&lli->lli_fid));
-		GOTO(out, rc = -ESTALE);
-	}
 
-	/* get parent reference count here, and put it in ll_statahead_thread */
-	parent = dget(dentry->d_parent);
-	if (unlikely(sai->sai_inode != parent->d_inode)) {
-		struct ll_inode_info *nlli = ll_i2info(parent->d_inode);
-
-		CWARN("Race condition, someone changed %.*s just now: "
-			"old parent "DFID", new parent "DFID"\n",
-			dentry->d_name.len, dentry->d_name.name,
-			PFID(&lli->lli_fid), PFID(&nlli->lli_fid));
-		dput(parent);
-		iput(sai->sai_inode);
-		GOTO(out, rc = -EAGAIN);
-	}
-
-	CDEBUG(D_READA, "start statahead thread: sai %p, parent %.*s\n",
-	       sai, parent->d_name.len, parent->d_name.name);
-
-	/* if another process started statahead thread, or deauthorized current
-	 * lli_opendir_key, don't start statahead. */
+	/* if current lli_opendir_key was deauthorized, or dir re-opened by
+	 * another process, don't start statahead, otherwise the newly spawned
+	 * statahead thread won't be notified to quit. */
 	spin_lock(&lli->lli_sa_lock);
 	if (unlikely(lli->lli_sai != NULL ||
 		     lli->lli_opendir_key == NULL ||
 		     lli->lli_opendir_pid != current->pid)) {
 		spin_unlock(&lli->lli_sa_lock);
-
-		dput(parent);
-		iput(sai->sai_inode);
-		GOTO(out, rc = -EAGAIN);
+		GOTO(out, rc = -EPERM);
 	}
 	lli->lli_sai = sai;
 	spin_unlock(&lli->lli_sa_lock);
 
 	atomic_inc(&ll_i2sbi(parent->d_inode)->ll_sa_running);
 
+	CDEBUG(D_READA, "start statahead thread: [pid %d] [parent %.*s]\n",
+	       current_pid(), parent->d_name.len, parent->d_name.name);
+
 	task = kthread_run(ll_statahead_thread, parent, "ll_sa_%u",
 			   lli->lli_opendir_pid);
 	thread = &sai->sai_thread;
 	if (IS_ERR(task)) {
 		rc = PTR_ERR(task);
-		CERROR("cannot start ll_sa thread: rc = %d\n", rc);
-		dput(parent);
-
-		spin_lock(&lli->lli_sa_lock);
-		thread_set_flags(thread, SVC_STOPPED);
-		thread_set_flags(&sai->sai_agl_thread, SVC_STOPPED);
-		spin_unlock(&lli->lli_sa_lock);
-
-		ll_sai_put(sai);
-		LASSERT(lli->lli_sai == NULL);
-		RETURN(-EAGAIN);
+		CERROR("can't start ll_sa thread, rc: %d\n", rc);
+		GOTO(out, rc);
 	}
 
 	l_wait_event(thread->t_ctl_waitq,
@@ -1582,29 +1593,35 @@ static int start_statahead_thread(struct inode *dir, struct dentry *dentry)
 	RETURN(-EAGAIN);
 
 out:
-	if (sai != NULL)
-		OBD_FREE_PTR(sai);
-
-	/* once we start statahead thread failed, disable statahead so
-	 * subsequent won't waste time to try it. */
+	/* once we start statahead thread failed, disable statahead so that
+	 * subsequent stat won't waste time to try it. */
 	spin_lock(&lli->lli_sa_lock);
 	lli->lli_sa_enabled = 0;
+	lli->lli_sai = NULL;
 	spin_unlock(&lli->lli_sa_lock);
 
+	if (sai != NULL)
+		ll_sai_free(sai);
+
 	RETURN(rc);
 }
 
 /**
- * Start statahead thread if this is the first dir entry.
- * Otherwise if a thread is started already, wait it until it is ahead of me.
- * \retval 1       -- find entry with lock in cache, the caller needs to do
- *		      nothing.
- * \retval 0       -- find entry in cache, but without lock, the caller needs
- *		      refresh from MDS.
- * \retval others  -- the caller need to process as non-statahead.
+ * statahead entry function, this is called when client getattr on a file, it
+ * will start statahead thread if this is the first dir entry, else revalidate
+ * dentry from statahead cache.
+ *
+ * \param[in]  dir	parent directory
+ * \param[out] dentryp	dentry to getattr
+ * \param[in]  unplug	unplug statahead window only (normally for negative
+ *			dentry)
+ * \retval		1 on success
+ * \retval		0 revalidation from statahead cache failed, caller needs
+ *			to getattr from server directly
+ * \retval		negative number on error, caller often ignores this and
+ *			then getattr from server
  */
-int do_statahead_enter(struct inode *dir, struct dentry **dentryp,
-		       int only_unplug)
+int ll_statahead(struct inode *dir, struct dentry **dentryp, bool unplug)
 {
 	struct ll_statahead_info *sai;
 
@@ -1612,13 +1629,11 @@ int do_statahead_enter(struct inode *dir, struct dentry **dentryp,
 	if (sai != NULL) {
 		int rc;
 
-		rc = revalidate_statahead_dentry(dir, sai, dentryp,
-						 only_unplug);
+		rc = revalidate_statahead_dentry(dir, sai, dentryp, unplug);
 		CDEBUG(D_READA, "revalidate statahead %.*s: %d.\n",
 			(*dentryp)->d_name.len, (*dentryp)->d_name.name, rc);
 		ll_sai_put(sai);
 		return rc;
 	}
-
 	return start_statahead_thread(dir, *dentryp);
 }