[PATCH 0/2] Prepare for constifying SCSI host templates

[PATCH 0/2] Prepare for constifying SCSI host templates

[Bart Van Assche]

Hi Martin,

This patch series prepares for constifying SCSI host templates by moving the
members that are not constant out of the SCSI host template. Please consider
this patch series for the next merge window.

Thanks,

Bart.

Bart Van Assche (2):
  scsi: esas2r: Introduce scsi_template_proc_dir()
  scsi: core: Introduce a new list for SCSI proc directory entries

 drivers/scsi/esas2r/esas2r_main.c |  18 +++--
 drivers/scsi/scsi_proc.c          | 106 ++++++++++++++++++++++++++----
 include/scsi/scsi_host.h          |  16 ++---
 3 files changed, 108 insertions(+), 32 deletions(-)

[PATCH 1/2] scsi: esas2r: Introduce scsi_template_proc_dir()

[Bart Van Assche]

Prepare for removing the 'proc_dir' and 'present' members from the SCSI
host template. This patch does not change any functionality.

Cc: Bradley Grove <linuxdrivers@attotech.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: John Garry <john.garry@huawei.com>
Cc: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/esas2r/esas2r_main.c | 18 +++++++++++-------
 drivers/scsi/scsi_proc.c          | 11 +++++++++++
 include/scsi/scsi_host.h          |  4 ++++
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/esas2r/esas2r_main.c b/drivers/scsi/esas2r/esas2r_main.c
index 7a4eadad23d7..fbf7fdb3b52a 100644
--- a/drivers/scsi/esas2r/esas2r_main.c
+++ b/drivers/scsi/esas2r/esas2r_main.c
@@ -248,7 +248,6 @@ static struct scsi_host_template driver_template = {
 	.sg_tablesize			= SG_CHUNK_SIZE,
 	.cmd_per_lun			=
 		ESAS2R_DEFAULT_CMD_PER_LUN,
-	.present			= 0,
 	.emulated			= 0,
 	.proc_name			= ESAS2R_DRVR_NAME,
 	.change_queue_depth		= scsi_change_queue_depth,
@@ -637,10 +636,13 @@ static void __exit esas2r_exit(void)
 	esas2r_log(ESAS2R_LOG_INFO, "%s called", __func__);
 
 	if (esas2r_proc_major > 0) {
+		struct proc_dir_entry *proc_dir;
+
 		esas2r_log(ESAS2R_LOG_INFO, "unregister proc");
 
-		remove_proc_entry(ATTONODE_NAME,
-				  esas2r_proc_host->hostt->proc_dir);
+		proc_dir = scsi_template_proc_dir(esas2r_proc_host->hostt);
+		if (proc_dir)
+			remove_proc_entry(ATTONODE_NAME, proc_dir);
 		unregister_chrdev(esas2r_proc_major, ESAS2R_DRVR_NAME);
 
 		esas2r_proc_major = 0;
@@ -730,11 +732,13 @@ const char *esas2r_info(struct Scsi_Host *sh)
 			       esas2r_proc_major);
 
 		if (esas2r_proc_major > 0) {
-			struct proc_dir_entry *pde;
+			struct proc_dir_entry *proc_dir;
+			struct proc_dir_entry *pde = NULL;
 
-			pde = proc_create(ATTONODE_NAME, 0,
-					  sh->hostt->proc_dir,
-					  &esas2r_proc_ops);
+			proc_dir = scsi_template_proc_dir(sh->hostt);
+			if (proc_dir)
+				pde = proc_create(ATTONODE_NAME, 0, proc_dir,
+						  &esas2r_proc_ops);
 
 			if (!pde) {
 				esas2r_log_dev(ESAS2R_LOG_WARN,
diff --git a/drivers/scsi/scsi_proc.c b/drivers/scsi/scsi_proc.c
index 95aee1ad1383..eeb9261c93f7 100644
--- a/drivers/scsi/scsi_proc.c
+++ b/drivers/scsi/scsi_proc.c
@@ -83,6 +83,17 @@ static int proc_scsi_host_open(struct inode *inode, struct file *file)
 				4 * PAGE_SIZE);
 }
 
+/**
+ * scsi_template_proc_dir() - returns the procfs dir for a SCSI host template
+ * @sht: SCSI host template pointer.
+ */
+struct proc_dir_entry *
+scsi_template_proc_dir(const struct scsi_host_template *sht)
+{
+	return sht->proc_dir;
+}
+EXPORT_SYMBOL(scsi_template_proc_dir);
+
 static const struct proc_ops proc_scsi_ops = {
 	.proc_open	= proc_scsi_host_open,
 	.proc_release	= single_release,
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index aa7b7496c93a..ff00caed7964 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -752,6 +752,10 @@ extern struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *, int);
 extern int __must_check scsi_add_host_with_dma(struct Scsi_Host *,
 					       struct device *,
 					       struct device *);
+#if defined(CONFIG_SCSI_PROC_FS)
+struct proc_dir_entry *
+scsi_template_proc_dir(const struct scsi_host_template *sht);
+#endif
 extern void scsi_scan_host(struct Scsi_Host *);
 extern void scsi_rescan_device(struct device *);
 extern void scsi_remove_host(struct Scsi_Host *);

[PATCH 2/2] scsi: core: Introduce a new list for SCSI proc directory entries

[Bart Van Assche]

Instead of using scsi_host_template members to track the SCSI proc
directory entries, track these entries in a list. This patch changes the
time needed for looking up the proc dir pointer from O(1) into O(n). I
think this is acceptable since the number of SCSI host adapter types per
host is usually small (less than ten).

This patch has been tested by attaching two USB storage devices to a
qemu host:

$ grep -aH . /proc/scsi/usb-storage/*
/proc/scsi/usb-storage/7:   Host scsi7: usb-storage
/proc/scsi/usb-storage/7:       Vendor: QEMU
/proc/scsi/usb-storage/7:      Product: QEMU USB HARDDRIVE
/proc/scsi/usb-storage/7:Serial Number: 1-0000:00:02.1:00.0-6
/proc/scsi/usb-storage/7:     Protocol: Transparent SCSI
/proc/scsi/usb-storage/7:    Transport: Bulk
/proc/scsi/usb-storage/7:       Quirks: SANE_SENSE
/proc/scsi/usb-storage/8:   Host scsi8: usb-storage
/proc/scsi/usb-storage/8:       Vendor: QEMU
/proc/scsi/usb-storage/8:      Product: QEMU USB HARDDRIVE
/proc/scsi/usb-storage/8:Serial Number: 1-0000:00:02.1:00.0-7
/proc/scsi/usb-storage/8:     Protocol: Transparent SCSI
/proc/scsi/usb-storage/8:    Transport: Bulk
/proc/scsi/usb-storage/8:       Quirks: SANE_SENSE

This patch prepares for constifying most SCSI host templates.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: John Garry <john.garry@huawei.com>
Cc: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_proc.c | 97 ++++++++++++++++++++++++++++++++++------
 include/scsi/scsi_host.h | 12 -----
 2 files changed, 83 insertions(+), 26 deletions(-)

diff --git a/drivers/scsi/scsi_proc.c b/drivers/scsi/scsi_proc.c
index eeb9261c93f7..702b78963c2e 100644
--- a/drivers/scsi/scsi_proc.c
+++ b/drivers/scsi/scsi_proc.c
@@ -43,8 +43,23 @@
 
 static struct proc_dir_entry *proc_scsi;
 
-/* Protect sht->present and sht->proc_dir */
+/* Protects scsi_proc_list */
 static DEFINE_MUTEX(global_host_template_mutex);
+static LIST_HEAD(scsi_proc_list);
+
+/**
+ * struct scsi_proc_entry - (host template, SCSI proc dir) association
+ * @entry: entry in scsi_proc_list.
+ * @sht: SCSI host template associated with the procfs directory.
+ * @proc_dir: procfs directory associated with the SCSI host template.
+ * @present: Number of SCSI hosts instantiated for @sht.
+ */
+struct scsi_proc_entry {
+	struct list_head	entry;
+	const struct scsi_host_template *sht;
+	struct proc_dir_entry	*proc_dir;
+	unsigned char		present;
+};
 
 static ssize_t proc_scsi_host_write(struct file *file, const char __user *buf,
                            size_t count, loff_t *ppos)
@@ -83,6 +98,32 @@ static int proc_scsi_host_open(struct inode *inode, struct file *file)
 				4 * PAGE_SIZE);
 }
 
+static struct scsi_proc_entry *
+__scsi_lookup_proc_entry(const struct scsi_host_template *sht)
+{
+	struct scsi_proc_entry *e;
+
+	lockdep_assert_held(&global_host_template_mutex);
+
+	list_for_each_entry(e, &scsi_proc_list, entry)
+		if (e->sht == sht)
+			return e;
+
+	return NULL;
+}
+
+static struct scsi_proc_entry *
+scsi_lookup_proc_entry(const struct scsi_host_template *sht)
+{
+	struct scsi_proc_entry *e;
+
+	mutex_lock(&global_host_template_mutex);
+	e = __scsi_lookup_proc_entry(sht);
+	mutex_unlock(&global_host_template_mutex);
+
+	return e;
+}
+
 /**
  * scsi_template_proc_dir() - returns the procfs dir for a SCSI host template
  * @sht: SCSI host template pointer.
@@ -90,7 +131,9 @@ static int proc_scsi_host_open(struct inode *inode, struct file *file)
 struct proc_dir_entry *
 scsi_template_proc_dir(const struct scsi_host_template *sht)
 {
-	return sht->proc_dir;
+	struct scsi_proc_entry *e = scsi_lookup_proc_entry(sht);
+
+	return e ? e->proc_dir : NULL;
 }
 EXPORT_SYMBOL(scsi_template_proc_dir);
 
@@ -111,17 +154,35 @@ static const struct proc_ops proc_scsi_ops = {
 
 void scsi_proc_hostdir_add(struct scsi_host_template *sht)
 {
+	struct scsi_proc_entry *e;
+
 	if (!sht->show_info)
 		return;
 
 	mutex_lock(&global_host_template_mutex);
-	if (!sht->present++) {
-		sht->proc_dir = proc_mkdir(sht->proc_name, proc_scsi);
-        	if (!sht->proc_dir)
-			printk(KERN_ERR "%s: proc_mkdir failed for %s\n",
-			       __func__, sht->proc_name);
+	e = __scsi_lookup_proc_entry(sht);
+	if (!e) {
+		e = kzalloc(sizeof(*e), GFP_KERNEL);
+		if (!e)
+			goto unlock;
+	}
+	if (e->present++) {
+		e = NULL;
+		goto unlock;
+	}
+	e->proc_dir = proc_mkdir(sht->proc_name, proc_scsi);
+	if (!e->proc_dir) {
+		printk(KERN_ERR "%s: proc_mkdir failed for %s\n", __func__,
+		       sht->proc_name);
+		goto unlock;
 	}
+	e->sht = sht;
+	list_add_tail(&e->entry, &scsi_proc_list);
+	e = NULL;
+unlock:
 	mutex_unlock(&global_host_template_mutex);
+
+	kfree(e);
 }
 
 /**
@@ -130,13 +191,17 @@ void scsi_proc_hostdir_add(struct scsi_host_template *sht)
  */
 void scsi_proc_hostdir_rm(struct scsi_host_template *sht)
 {
+	struct scsi_proc_entry *e;
+
 	if (!sht->show_info)
 		return;
 
 	mutex_lock(&global_host_template_mutex);
-	if (!--sht->present && sht->proc_dir) {
+	e = __scsi_lookup_proc_entry(sht);
+	if (e && !--e->present) {
 		remove_proc_entry(sht->proc_name, proc_scsi);
-		sht->proc_dir = NULL;
+		list_del(&e->entry);
+		kfree(e);
 	}
 	mutex_unlock(&global_host_template_mutex);
 }
@@ -149,15 +214,17 @@ void scsi_proc_hostdir_rm(struct scsi_host_template *sht)
 void scsi_proc_host_add(struct Scsi_Host *shost)
 {
 	struct scsi_host_template *sht = shost->hostt;
+	struct scsi_proc_entry *e;
 	struct proc_dir_entry *p;
 	char name[10];
 
-	if (!sht->proc_dir)
+	e = scsi_lookup_proc_entry(sht);
+	if (!e)
 		return;
 
 	sprintf(name,"%d", shost->host_no);
-	p = proc_create_data(name, S_IRUGO | S_IWUSR,
-		sht->proc_dir, &proc_scsi_ops, shost);
+	p = proc_create_data(name, S_IRUGO | S_IWUSR, e->proc_dir,
+			     &proc_scsi_ops, shost);
 	if (!p)
 		printk(KERN_ERR "%s: Failed to register host %d in"
 		       "%s\n", __func__, shost->host_no,
@@ -170,13 +237,15 @@ void scsi_proc_host_add(struct Scsi_Host *shost)
  */
 void scsi_proc_host_rm(struct Scsi_Host *shost)
 {
+	struct scsi_proc_entry *e;
 	char name[10];
 
-	if (!shost->hostt->proc_dir)
+	e = scsi_lookup_proc_entry(shost->hostt);
+	if (!e)
 		return;
 
 	sprintf(name,"%d", shost->host_no);
-	remove_proc_entry(name, shost->hostt->proc_dir);
+	remove_proc_entry(name, e->proc_dir);
 }
 /**
  * proc_print_scsidevice - return data about this host
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index ff00caed7964..644865fa9c29 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -357,12 +357,6 @@ struct scsi_host_template {
 	 */
 	const char *proc_name;
 
-	/*
-	 * Used to store the procfs directory if a driver implements the
-	 * show_info method.
-	 */
-	struct proc_dir_entry *proc_dir;
-
 	/*
 	 * This determines if we will use a non-interrupt driven
 	 * or an interrupt driven scheme.  It is set to the maximum number
@@ -423,12 +417,6 @@ struct scsi_host_template {
 	 */
 	short cmd_per_lun;
 
-	/*
-	 * present contains counter indicating how many boards of this
-	 * type were found when we did the scan.
-	 */
-	unsigned char present;
-
 	/* If use block layer to manage tags, this is tag allocation policy */
 	int tag_alloc_policy;