[SSI] openssi/kernel/cluster/ssi/util rmtfb.c,1.34,1.35

Update of /cvsroot/ssic-linux/openssi/kernel/cluster/ssi/util
In directory sfp-cvsdas-3.v30.ch3.sourceforge.com:/tmp/cvs-serv2164/cluster/ssi/util

Modified Files:
      Tag: OPENSSI-FC
	rmtfb.c 
Log Message:
cluster/ssi/util/rmtfb.c (#ifdef RMTFB_HASH_LOCKLESS)
- rmtfb_getcli_id: remove retry of __rmtfb_getcli_id(). SMP-safe.
- rmtfb_newcli: no longer do early check for an existing rmtfb_cli struct with same rfb_id. caller already checked. in one possible code path we were doing total of three checks.
- rmtfb_newcli: remove retry of __rmtfb_getcli_id(). SMP-safe.
- rmtfb_newcli: move rmtfb_setcli_re/open() till after we've added the rmtfb_cli structure to the hashed chained linked list to avoid racing with rmtfb_rclose(). fix -ERFB_TRYAGAIN error when rmtfb_rclose() lost the race.
- rmtfb_newcli: add comment before function about circular reference between file struct and rmtfb_cli struct.
- __rmtfb_getcli_id: no need to return -ERFB_RELEASE error. just return NULL since there is nothing for caller to do.
- __rmtfb_getcli_id: wait for rmtfb_setcli_re/open() completion. return -EREMOTE on failure.

cluster/ssi/util/rmtfb.c (#ifdef REOP_EXPORT_PATH_SVRNODE)
- rmtfb_getcli_id: indicate to compiler unlikely branch direction.


Index: rmtfb.c
===================================================================
RCS file: /cvsroot/ssic-linux/openssi/kernel/cluster/ssi/util/rmtfb.c,v
retrieving revision 1.34
retrieving revision 1.35
diff -u -d -r1.34 -r1.35
--- rmtfb.c	17 Jan 2011 06:33:53 -0000	1.34
+++ rmtfb.c	17 Jan 2011 07:05:45 -0000	1.35
@@ -50,9 +50,10 @@
 #include <cluster/gen/ics_rmtfb_macros_gen.h>
 #include <cluster/gen/ics_rmtfb_protos_gen.h>
 
+#ifndef RMTFB_HASH_LOCKLESS
 #define ERFB_RELEASE	700
-
 #define rmtfb_maxloops HZ
+#endif
 
 #ifdef RFBDEBUG
 #define RMTFB_MAGIC 0xDEAD2A9E
@@ -964,22 +965,42 @@
 
 #ifdef RMTFB_HASH_LOCKLESS
 static struct rmtfb_cli *
-__rmtfb_getcli_id(unsigned long id)
+__rmtfb_getcli_id(unsigned long id, struct semaphore *sem)
 {
 	struct rmtfb_cli *rfb;
+	task_t *curtask;
+	sigset_t oldmask;
 
-	rfb = (struct rmtfb_cli *) rmtfb_getcmn(
-					&rmtfb_clitbl[rfbhash(id)],
-					rmtfb_test_id,
-					(void *)&id);
+#ifdef RFBDEBUG
+	SSI_ASSERT(!sem || sem_owned(sem));
+#endif
+	rfb = (typeof(rfb)) rmtfb_getcmn(&rmtfb_clitbl[rfbhash(id)],
+					rmtfb_test_id, (void *)&id);
 	if (!rfb)
 		return NULL;
-
 	/* Do implicit get_file() */
 	if (!atomic_test_and_add(1, &rfb->common.rfb_file->f_count)) {
 		/* Lost race with final fput() */
 		rmtfb_putcli(rfb);
-		return ERR_PTR(-ERFB_RELEASE);
+		return NULL;
+	}
+	/* Got a valid rmtfb_cli structure */
+	if (sem)
+		up(sem);
+
+	if (!atomic_read(&rfb->rfb_state)) {
+		curtask = current;
+		ssi_block_signals(curtask, &oldmask);
+		/* Wait for rmtfb_setcli_re/open() */
+		wait_event_interruptible(rfb->rfb_wait,
+					 atomic_read(&rfb->rfb_state));
+		ssi_unblock_signals(curtask, &oldmask);
+	}
+	if (unlikely(atomic_read(&rfb->rfb_state) == 2)) {
+		/* rmtfb_setcli_re/open() failed */
+		fput(rfb->common.rfb_file);
+		rmtfb_putcli(rfb);
+		return ERR_PTR(-EREMOTE);
 	}
 	return rfb;
 }
@@ -1040,11 +1061,13 @@
 {
 	struct rmtfb_cli *rfb;
 	struct file *file;
-	int loop;
+#ifndef RMTFB_HASH_LOCKLESS
+	int loop = 0;
+#endif
 #ifdef REOP_EXPORT_PATH_SVRNODE
 	int svr = 0;
 
-	if (!path || !(svr = path->svrnode) || inval(id,svr)) {
+	if (unlikely(!path || !(svr = path->svrnode) || inval(id,svr))) {
 #else
 	if (!path || !svr || inval(id,svr)) {
 #endif
@@ -1056,25 +1079,11 @@
 		return ERR_PTR(-EINVAL);
 	}
 
-	loop = 0;
 #ifdef RMTFB_HASH_LOCKLESS
-	for (;;) {
-		rfb = __rmtfb_getcli_id(id);
-		if (!rfb)
-			break;
-		if (PTR_ERR(rfb) != -ERFB_RELEASE)
-			goto out;
-		/* Avoids a race where clrcli and setcli could
-		 * be received out of order at the server,
-		 * leaving it unaware that this node is its
-		 * client again.
-		 */
-		if (++loop > rmtfb_maxloops) {
-			printk(KERN_INFO "rmtfb_getcli_id: looping\n");
-			loop = 0;
-		}
-		yield();
-	}
+	/* See if another import made one already */
+	rfb = __rmtfb_getcli_id(id, NULL);
+	if (rfb || IS_ERR(rfb))
+		goto out;
 #else /* RMTFB_HASH_LOCKLESS */
 repeat:
 	LOCK_SHR_RW_LOCK(&rmtfb_clitbl_lock);
@@ -1202,6 +1211,10 @@
 		rfb->rfb_magic = RMTFB_MAGIC;
 #endif
 		rfb->rfb_server = svr;
+#ifdef RMTFB_HASH_LOCKLESS
+		atomic_set(&rfb->rfb_state, 0);
+		init_waitqueue_head(&rfb->rfb_wait);
+#endif
 	}
 	return rfb;
 }
@@ -1405,33 +1418,27 @@
  *
  * NOTE! fput() is called on @file before returning to caller if there is an
  * existing rmtfb_cli structure with the same rfb_id.
+ *
+ * Also get_file() is not invoked on @file to increment f_count because of the
+ * circular reference file->private_data = rfb and rfb->common.rfb_file = file.
+ * The file structure has the active reference to rmtfb_cli structure but not
+ * the other way around.
  */
 struct rmtfb_cli *
 rmtfb_newcli(struct file *file, unsigned long id,
 	     clusternode_t svr, char noremote)
 {
 static DECLARE_MUTEX(rmtfb_newcli_lock);
-	struct rmtfb_cli *rfb;
+	struct rmtfb_cli *rfb, *old;
 	unsigned long hash;
 	int error;
 	char import;
 
-	if (id) {
-		/* Fast check: see if another import didn't make one already */
-		rfb = __rmtfb_getcli_id(id);
-		if (rfb && !IS_ERR(rfb)) {
-			/* BUG: ssi_sockfs_make_cli() expects no race */
-			BUG_ON(noremote);
-			fput(file); /* rfb->common.rfb_file != file */
-			return rfb;
-		}
-	}
-
 	if (unlikely(file->private_data)) {
 		printk(KERN_ERR "%s: non-exportable filesystem (%s)\n",
 			__FUNCTION__, file->f_vfsmnt->mnt_sb->s_type->name);
 		error = -EOPNOTSUPP;
-		goto out;
+		goto out_bad;
 	}
 
 	SSI_ASSERT(svr && !inval(1,svr));
@@ -1439,61 +1446,28 @@
 	rfb = rmtfb_cli_alloc(file, id, svr);
 	if (!rfb) {
 		error = -ENOMEM;
-		goto out;
+		goto out_bad;
 	}
 	import = !!id;
 	if (!id)
 		id = rfb->common.rfb_id;
 
-	if (!noremote) {
-		if (import)
-			error = rmtfb_setcli_reopen(rfb);
-		else
-			error = rmtfb_setcli_open(rfb);
-		SSI_ASSERT(error != -EINVAL);
-		if (unlikely(error)) {
-			rmtfb_freecli(rfb);
-			goto out;
-		}
-	} else
-		error = 0;
-
 	hash = rfbhash(id);
-
 	down(&rmtfb_newcli_lock);
-
 	if (import) {
-		struct rmtfb_cli *old;
-		int loop = 0;
-
 		/* Make sure another import didn't make one already */
-		for (;;) {
-			old = __rmtfb_getcli_id(id);
-			if (!old || PTR_ERR(old) != -ERFB_RELEASE)
-				break;
-			up(&rmtfb_newcli_lock);
-			/* Avoids a race where clrcli and setcli could
-			 * be received out of order at the server,
-			 * leaving it unaware that this node is its
-			 * client again.
-			 */
-			if (++loop > rmtfb_maxloops) {
-				printk(KERN_INFO "rmtfb_newcli: looping\n");
-				loop = 0;
-			}
-			yield();
-			down(&rmtfb_newcli_lock);
-		}
-		if (unlikely(old)) {
-			up(&rmtfb_newcli_lock);
-			/* NB: No need to undo rmtfb_setcli_re/open() */
+		old = __rmtfb_getcli_id(id, &rmtfb_newcli_lock);
+		if (old) {
+			/* rmtfb_newcli_lock released */
 			rmtfb_freecli(rfb);
-			rfb = old;
-			if (!IS_ERR(rfb)) {
-				/* BUG: ssi_sockfs_make_cli() expects no race */
-				BUG_ON(noremote);
-				fput(file); /* rfb->common.rfb_file != file */
+			if (IS_ERR(old)) {
+				error = PTR_ERR(old);
+				goto out_bad;
 			}
+			rfb = old;
+			/* BUG: ssi_sockfs_make_cli() expects no race */
+			BUG_ON(noremote);
+			fput(file); /* rfb->common.rfb_file != file */
 			goto out;
 		}
 	}
@@ -1516,19 +1490,39 @@
 	hlist_add_head_rcu(&rfb->common.rfb_hash, &rmtfb_clitbl[hash]);
 	spin_unlock(&rmtfb_clitbl_lock);
 	up(&rmtfb_newcli_lock);
-out:
-	if (error) {
-#ifdef RFBDEBUG
-		printk(KERN_DEBUG "rmtfb_newcli: fail error=%d ino=%lu name=%s",
-			error, ftoi(file)->i_ino, file->f_dentry->d_name.name);
-#endif
-		return ERR_PTR(error);
+
+	if (!noremote) {
+		/* We save this part for last to ensure there is no other
+		 * rmtfb_cli struct with the same rfb_id. We avoid racing with
+		 * rmtfb_rclose(). If we won the race the next rmtfb_rclose()
+		 * could see -ERFB_TRYAGAIN from the server.
+		 */
+		if (import) {
+			error = rmtfb_setcli_reopen(rfb);
+		} else
+			error = rmtfb_setcli_open(rfb);
+		if (unlikely(error)) {
+			SSI_ASSERT(error != -EINVAL);
+			atomic_set(&rfb->rfb_state, 2); /* stale */
+			wake_up(&rfb->rfb_wait);
+			rmtfb_putcli(rfb);
+			goto out_bad;
+		}
 	}
+	atomic_set(&rfb->rfb_state, 1); /* ready */
+	wake_up(&rfb->rfb_wait);
+out:
 #ifdef RFBDEBUG
 	printk(KERN_DEBUG "rfb_server=%u ", svr);
 	rmtfb_cli_debug("rmtfb_newcli:",rfb);
 #endif
 	return rfb;
+out_bad:
+#ifdef RFBDEBUG
+	printk(KERN_DEBUG "rmtfb_newcli: fail error=%d ino=%lu name=%s",
+		error, ftoi(file)->i_ino, file->f_dentry->d_name.name);
+#endif
+	return ERR_PTR(error);
 }
 #else /* RMTFB_HASH_LOCKLESS */
 struct rmtfb_cli *


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