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Date:   Wed, 24 Oct 2018 01:00:26 +0100
From:   David Howells <dhowells@...hat.com>
To:     viro@...iv.linux.org.uk
Cc:     dhowells@...hat.com, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 22/25] afs: Allow dumping of server cursor on operation
 failure [ver #2]

Provide an option to allow the file or volume location server cursor to be
dumped if the rotation routine falls off the end without managing to
contact a server.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/Kconfig     |   12 +++++++++++
 fs/afs/addr_list.c |    2 ++
 fs/afs/internal.h  |    3 +++
 fs/afs/rotate.c    |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/afs/vl_rotate.c |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 127 insertions(+)

diff --git a/fs/afs/Kconfig b/fs/afs/Kconfig
index ebba3b18e5da..701aaa9b1899 100644
--- a/fs/afs/Kconfig
+++ b/fs/afs/Kconfig
@@ -27,3 +27,15 @@ config AFS_FSCACHE
 	help
 	  Say Y here if you want AFS data to be cached locally on disk through
 	  the generic filesystem cache manager
+
+config AFS_DEBUG_CURSOR
+	bool "AFS server cursor debugging"
+	depends on AFS_FS
+	help
+	  Say Y here to cause the contents of a server cursor to be dumped to
+	  the dmesg log if the server rotation algorithm fails to successfully
+	  contact a server.
+
+	  See <file:Documentation/filesystems/afs.txt> for more information.
+
+	  If unsure, say N.
diff --git a/fs/afs/addr_list.c b/fs/afs/addr_list.c
index 3f60b4012587..bc5ce31a4ae4 100644
--- a/fs/afs/addr_list.c
+++ b/fs/afs/addr_list.c
@@ -358,6 +358,8 @@ bool afs_iterate_addresses(struct afs_addr_cursor *ac)
 	if (!ac->alist)
 		return false;
 
+	ac->nr_iterations++;
+
 	if (ac->begun) {
 		ac->index++;
 		if (ac->index == ac->alist->nr_addrs)
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index ce79bd514331..ac9da1e4050e 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -660,6 +660,7 @@ struct afs_addr_cursor {
 	short			error;
 	bool			begun;		/* T if we've begun iteration */
 	bool			responded;	/* T if the current address responded */
+	unsigned short		nr_iterations;	/* Number of address iterations */
 };
 
 /*
@@ -677,6 +678,7 @@ struct afs_vl_cursor {
 #define AFS_VL_CURSOR_STOP	0x0001		/* Set to cease iteration */
 #define AFS_VL_CURSOR_RETRY	0x0002		/* Set to do a retry */
 #define AFS_VL_CURSOR_RETRIED	0x0004		/* Set if started a retry */
+	unsigned short		nr_iterations;	/* Number of server iterations */
 };
 
 /*
@@ -700,6 +702,7 @@ struct afs_fs_cursor {
 #define AFS_FS_CURSOR_VNOVOL	0x0008		/* Set if seen VNOVOL */
 #define AFS_FS_CURSOR_CUR_ONLY	0x0010		/* Set if current server only (file lock held) */
 #define AFS_FS_CURSOR_NO_VSLEEP	0x0020		/* Set to prevent sleep on VBUSY, VOFFLINE, ... */
+	unsigned short		nr_iterations;	/* Number of server iterations */
 };
 
 /*
diff --git a/fs/afs/rotate.c b/fs/afs/rotate.c
index 41405dde0113..7c4487781637 100644
--- a/fs/afs/rotate.c
+++ b/fs/afs/rotate.c
@@ -156,6 +156,8 @@ bool afs_select_fileserver(struct afs_fs_cursor *fc)
 		return false;
 	}
 
+	fc->nr_iterations++;
+
 	/* Evaluate the result of the previous operation, if there was one. */
 	switch (error) {
 	case SHRT_MAX:
@@ -519,6 +521,56 @@ bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
 	return false;
 }
 
+/*
+ * Dump cursor state in the case of the error being EDESTADDRREQ.
+ */
+static void afs_dump_edestaddrreq(const struct afs_fs_cursor *fc)
+{
+	static int count;
+	int i;
+
+	if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
+		return;
+	count++;
+
+	rcu_read_lock();
+
+	pr_notice("EDESTADDR occurred\n");
+	pr_notice("FC: cbb=%x cbb2=%x fl=%hx err=%hd\n",
+		  fc->cb_break, fc->cb_break_2, fc->flags, fc->error);
+	pr_notice("FC: st=%u ix=%u ni=%u\n",
+		  fc->start, fc->index, fc->nr_iterations);
+
+	if (fc->server_list) {
+		const struct afs_server_list *sl = fc->server_list;
+		pr_notice("FC: SL nr=%u ix=%u vnov=%hx\n",
+			  sl->nr_servers, sl->index, sl->vnovol_mask);
+		for (i = 0; i < sl->nr_servers; i++) {
+			const struct afs_server *s = sl->servers[i].server;
+			pr_notice("FC: server fl=%lx av=%u %pU\n",
+				  s->flags, s->addr_version, &s->uuid);
+			if (s->addresses) {
+				const struct afs_addr_list *a =
+					rcu_dereference(s->addresses);
+				pr_notice("FC:  - av=%u nr=%u/%u/%u ax=%u\n",
+					  a->version,
+					  a->nr_ipv4, a->nr_addrs, a->max_addrs,
+					  a->index);
+				pr_notice("FC:  - pr=%lx yf=%lx\n",
+					  a->probed, a->yfs);
+				if (a == fc->ac.alist)
+					pr_notice("FC:  - current\n");
+			}
+		}
+	}
+
+	pr_notice("AC: as=%u ax=%u ac=%d er=%d b=%u r=%u ni=%u\n",
+		  fc->ac.start, fc->ac.index, fc->ac.abort_code, fc->ac.error,
+		  fc->ac.begun, fc->ac.responded, fc->ac.nr_iterations);
+
+	rcu_read_unlock();
+}
+
 /*
  * Tidy up a filesystem cursor and unlock the vnode.
  */
@@ -526,6 +578,11 @@ int afs_end_vnode_operation(struct afs_fs_cursor *fc)
 {
 	struct afs_net *net = afs_v2net(fc->vnode);
 
+	if (fc->error == -EDESTADDRREQ ||
+	    fc->error == -ENETUNREACH ||
+	    fc->error == -EHOSTUNREACH)
+		afs_dump_edestaddrreq(fc);
+
 	mutex_unlock(&fc->vnode->io_lock);
 
 	afs_end_cursor(&fc->ac);
diff --git a/fs/afs/vl_rotate.c b/fs/afs/vl_rotate.c
index 44a936ad9c7a..5b99ea7be194 100644
--- a/fs/afs/vl_rotate.c
+++ b/fs/afs/vl_rotate.c
@@ -83,6 +83,8 @@ bool afs_select_vlserver(struct afs_vl_cursor *vc)
 		return false;
 	}
 
+	vc->nr_iterations++;
+
 	/* Evaluate the result of the previous operation, if there was one. */
 	switch (error) {
 	case SHRT_MAX:
@@ -234,6 +236,52 @@ bool afs_select_vlserver(struct afs_vl_cursor *vc)
 	return false;
 }
 
+/*
+ * Dump cursor state in the case of the error being EDESTADDRREQ.
+ */
+static void afs_vl_dump_edestaddrreq(const struct afs_vl_cursor *vc)
+{
+	static int count;
+	int i;
+
+	if (!IS_ENABLED(CONFIG_AFS_DEBUG_CURSOR) || count > 3)
+		return;
+	count++;
+
+	rcu_read_lock();
+	pr_notice("EDESTADDR occurred\n");
+	pr_notice("VC: st=%u ix=%u ni=%hu fl=%hx err=%hd\n",
+		  vc->start, vc->index, vc->nr_iterations, vc->flags, vc->error);
+
+	if (vc->server_list) {
+		const struct afs_vlserver_list *sl = vc->server_list;
+		pr_notice("VC: SL nr=%u ix=%u\n",
+			  sl->nr_servers, sl->index);
+		for (i = 0; i < sl->nr_servers; i++) {
+			const struct afs_vlserver *s = sl->servers[i].server;
+			pr_notice("VC: server fl=%lx %s+%hu\n",
+				  s->flags, s->name, s->port);
+			if (s->addresses) {
+				const struct afs_addr_list *a =
+					rcu_dereference(s->addresses);
+				pr_notice("VC:  - av=%u nr=%u/%u/%u ax=%u\n",
+					  a->version,
+					  a->nr_ipv4, a->nr_addrs, a->max_addrs,
+					  a->index);
+				pr_notice("VC:  - pr=%lx yf=%lx\n",
+					  a->probed, a->yfs);
+				if (a == vc->ac.alist)
+					pr_notice("VC:  - current\n");
+			}
+		}
+	}
+
+	pr_notice("AC: as=%u ax=%u ac=%d er=%d b=%u r=%u ni=%hu\n",
+		  vc->ac.start, vc->ac.index, vc->ac.abort_code, vc->ac.error,
+		  vc->ac.begun, vc->ac.responded, vc->ac.nr_iterations);
+	rcu_read_unlock();
+}
+
 /*
  * Tidy up a volume location server cursor and unlock the vnode.
  */
@@ -241,6 +289,11 @@ int afs_end_vlserver_operation(struct afs_vl_cursor *vc)
 {
 	struct afs_net *net = vc->cell->net;
 
+	if (vc->error == -EDESTADDRREQ ||
+	    vc->error == -ENETUNREACH ||
+	    vc->error == -EHOSTUNREACH)
+		afs_vl_dump_edestaddrreq(vc);
+
 	afs_end_cursor(&vc->ac);
 	afs_put_vlserverlist(net, vc->server_list);
 

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