Handle STATUS_IO_TIMEOUT gracefully

Currently STATUS_IO_TIMEOUT is not treated as retriable error.
It is currently mapped to ETIMEDOUT and returned to userspace
for most system calls. STATUS_IO_TIMEOUT is returned by server
in case of unavailability or throttling errors.

This patch will map the STATUS_IO_TIMEOUT to EAGAIN, so that it
can be retried. Also, added a check to drop the connection to
not overload the server in case of ongoing unavailability.
Signed-off-by: Rohith Surabattula <rohiths@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsglob.h

@@ -510,6 +510,8 @@ struct smb_version_operations {
 		      struct fiemap_extent_info *, u64, u64);
 	/* version specific llseek implementation */
 	loff_t (*llseek)(struct file *, struct cifs_tcon *, loff_t, int);
+	/* Check for STATUS_IO_TIMEOUT */
+	bool (*is_status_io_timeout)(char *buf);
 };
 
 struct smb_version_values {

fs/cifs/connect.c

@@ -69,6 +69,9 @@ extern bool disable_legacy_dialects;
 #define TLINK_ERROR_EXPIRE	(1 * HZ)
 #define TLINK_IDLE_EXPIRE	(600 * HZ)
 
+/* Drop the connection to not overload the server */
+#define NUM_STATUS_IO_TIMEOUT   5
+
 enum {
 	/* Mount options that take no arguments */
 	Opt_user_xattr, Opt_nouser_xattr,
@@ -1117,7 +1120,7 @@ cifs_demultiplex_thread(void *p)
 	struct task_struct *task_to_wake = NULL;
 	struct mid_q_entry *mids[MAX_COMPOUND];
 	char *bufs[MAX_COMPOUND];
-	unsigned int noreclaim_flag;
+	unsigned int noreclaim_flag, num_io_timeout = 0;
 
 	noreclaim_flag = memalloc_noreclaim_save();
 	cifs_dbg(FYI, "Demultiplex PID: %d\n", task_pid_nr(current));
@@ -1213,6 +1216,16 @@ cifs_demultiplex_thread(void *p)
 			continue;
 		}
 
+		if (server->ops->is_status_io_timeout &&
+		    server->ops->is_status_io_timeout(buf)) {
+			num_io_timeout++;
+			if (num_io_timeout > NUM_STATUS_IO_TIMEOUT) {
+				cifs_reconnect(server);
+				num_io_timeout = 0;
+				continue;
+			}
+		}
+
 		server->lstrp = jiffies;
 
 		for (i = 0; i < num_mids; i++) {

fs/cifs/smb2maperror.c

@@ -488,7 +488,7 @@ static const struct status_to_posix_error smb2_error_map_table[] = {
 	{STATUS_PIPE_CONNECTED, -EIO, "STATUS_PIPE_CONNECTED"},
 	{STATUS_PIPE_LISTENING, -EIO, "STATUS_PIPE_LISTENING"},
 	{STATUS_INVALID_READ_MODE, -EIO, "STATUS_INVALID_READ_MODE"},
-	{STATUS_IO_TIMEOUT, -ETIMEDOUT, "STATUS_IO_TIMEOUT"},
+	{STATUS_IO_TIMEOUT, -EAGAIN, "STATUS_IO_TIMEOUT"},
 	{STATUS_FILE_FORCED_CLOSED, -EIO, "STATUS_FILE_FORCED_CLOSED"},
 	{STATUS_PROFILING_NOT_STARTED, -EIO, "STATUS_PROFILING_NOT_STARTED"},
 	{STATUS_PROFILING_NOT_STOPPED, -EIO, "STATUS_PROFILING_NOT_STOPPED"},

fs/cifs/smb2ops.c

@@ -2354,6 +2354,17 @@ smb2_is_session_expired(char *buf)
 	return true;
 }
 
+static bool
+smb2_is_status_io_timeout(char *buf)
+{
+	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buf;
+
+	if (shdr->Status == STATUS_IO_TIMEOUT)
+		return true;
+	else
+		return false;
+}
+
 static int
 smb2_oplock_response(struct cifs_tcon *tcon, struct cifs_fid *fid,
 		     struct cifsInodeInfo *cinode)
@@ -4817,6 +4828,7 @@ struct smb_version_operations smb20_operations = {
 	.make_node = smb2_make_node,
 	.fiemap = smb3_fiemap,
 	.llseek = smb3_llseek,
+	.is_status_io_timeout = smb2_is_status_io_timeout,
 };
 
 struct smb_version_operations smb21_operations = {
@@ -4917,6 +4929,7 @@ struct smb_version_operations smb21_operations = {
 	.make_node = smb2_make_node,
 	.fiemap = smb3_fiemap,
 	.llseek = smb3_llseek,
+	.is_status_io_timeout = smb2_is_status_io_timeout,
 };
 
 struct smb_version_operations smb30_operations = {
@@ -5027,6 +5040,7 @@ struct smb_version_operations smb30_operations = {
 	.make_node = smb2_make_node,
 	.fiemap = smb3_fiemap,
 	.llseek = smb3_llseek,
+	.is_status_io_timeout = smb2_is_status_io_timeout,
 };
 
 struct smb_version_operations smb311_operations = {
@@ -5138,6 +5152,7 @@ struct smb_version_operations smb311_operations = {
 	.make_node = smb2_make_node,
 	.fiemap = smb3_fiemap,
 	.llseek = smb3_llseek,
+	.is_status_io_timeout = smb2_is_status_io_timeout,
 };
 
 struct smb_version_values smb20_values = {