[PATCH V6 0/3] scsi: Configure number of LUs reported by 'report-luns'

[PATCH V6 0/3] scsi: Configure number of LUs reported by 'report-luns'

[Rob Evers]

This patch set retrieves the number of LUs available on a target
using the report-luns command by re-sizing the returned data
buffer and retrying report luns.

A minor bug fix is included.

scsi_mod parameter max_report_luns is no longer used and is removed.

Changes from previous posting:

 - remove exteraneous else

 - remove INITIAL_MAX_REPORT_LUNS, hardwire buffer sizing, and touch up
   related comment

Rob Evers (3):
  scsi: Avoid unnecessary GFP_ATOMIC allocation in scsi_report_lun_scan
  scsi: Use set/get_unaligned_be32 in report_luns
  scsi: retry report-luns when reported LU count requres more memory

 drivers/scsi/scsi_scan.c | 54 ++++++++++++++----------------------------------
 1 file changed, 15 insertions(+), 39 deletions(-)

-- 
1.8.3.1

[PATCH V6 1/3] scsi: Avoid unnecessary GFP_ATOMIC allocation in scsi_report_lun_scan

[Rob Evers]

Signed-off-by: Rob Evers <revers@redhat.com>
---
 drivers/scsi/scsi_scan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index ba3f1e8..e460b35 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1408,7 +1408,7 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
 	 * prevent us from finding any LUNs on this target.
 	 */
 	length = (max_scsi_report_luns + 1) * sizeof(struct scsi_lun);
-	lun_data = kmalloc(length, GFP_ATOMIC |
+	lun_data = kmalloc(length, GFP_KERNEL |
 			   (sdev->host->unchecked_isa_dma ? __GFP_DMA : 0));
 	if (!lun_data) {
 		printk(ALLOC_FAILURE_MSG, __func__);
-- 
1.8.3.1

[PATCH V6 2/3] scsi: Use set/get_unaligned_be32 in report_luns

[Rob Evers]

Signed-off-by: Rob Evers <revers@redhat.com>
---
 drivers/scsi/scsi_scan.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index e460b35..8db1f6f 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -34,6 +34,7 @@
 #include <linux/spinlock.h>
 #include <linux/async.h>
 #include <linux/slab.h>
+#include <asm/unaligned.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -1359,7 +1360,6 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
 	unsigned int retries;
 	int result;
 	struct scsi_lun *lunp, *lun_data;
-	u8 *data;
 	struct scsi_sense_hdr sshdr;
 	struct scsi_device *sdev;
 	struct Scsi_Host *shost = dev_to_shost(&starget->dev);
@@ -1425,10 +1425,7 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
 	/*
 	 * bytes 6 - 9: length of the command.
 	 */
-	scsi_cmd[6] = (unsigned char) (length >> 24) & 0xff;
-	scsi_cmd[7] = (unsigned char) (length >> 16) & 0xff;
-	scsi_cmd[8] = (unsigned char) (length >> 8) & 0xff;
-	scsi_cmd[9] = (unsigned char) length & 0xff;
+	put_unaligned_be32(length, &scsi_cmd[6]);
 
 	scsi_cmd[10] = 0;	/* reserved */
 	scsi_cmd[11] = 0;	/* control */
@@ -1476,9 +1473,7 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
 	/*
 	 * Get the length from the first four bytes of lun_data.
 	 */
-	data = (u8 *) lun_data->scsi_lun;
-	length = ((data[0] << 24) | (data[1] << 16) |
-		  (data[2] << 8) | (data[3] << 0));
+	length = get_unaligned_be32(lun_data->scsi_lun);
 
 	num_luns = (length / sizeof(struct scsi_lun));
 	if (num_luns > max_scsi_report_luns) {
-- 
1.8.3.1

[PATCH V6 3/3] scsi: retry report-luns when reported LU count requres more memory

[Rob Evers]

Update scsi_report_lun_scan to initially always report up to 511 LUs,
as the previous default max_report_luns did.  Retry in a loop if not
enough memory is available for the number of LUs reported.  Parameter
max_report_luns is removed as it is no longer used.

Signed-off-by: Rob Evers <revers@redhat.com>
---
 drivers/scsi/scsi_scan.c | 41 +++++++++++------------------------------
 1 file changed, 11 insertions(+), 30 deletions(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 8db1f6f..88eee50 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -99,20 +99,6 @@ char scsi_scan_type[6] = SCSI_SCAN_TYPE_DEFAULT;
 module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO);
 MODULE_PARM_DESC(scan, "sync, async or none");
 
-/*
- * max_scsi_report_luns: the maximum number of LUNS that will be
- * returned from the REPORT LUNS command. 8 times this value must
- * be allocated. In theory this could be up to an 8 byte value, but
- * in practice, the maximum number of LUNs suppored by any device
- * is about 16k.
- */
-static unsigned int max_scsi_report_luns = 511;
-
-module_param_named(max_report_luns, max_scsi_report_luns, uint, S_IRUGO|S_IWUSR);
-MODULE_PARM_DESC(max_report_luns,
-		 "REPORT LUNS maximum number of LUNS received (should be"
-		 " between 1 and 16384)");
-
 static unsigned int scsi_inq_timeout = SCSI_TIMEOUT/HZ + 18;
 
 module_param_named(inq_timeout, scsi_inq_timeout, uint, S_IRUGO|S_IWUSR);
@@ -1399,15 +1385,11 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
 
 	/*
 	 * Allocate enough to hold the header (the same size as one scsi_lun)
-	 * plus the max number of luns we are requesting.
-	 *
-	 * Reallocating and trying again (with the exact amount we need)
-	 * would be nice, but then we need to somehow limit the size
-	 * allocated based on the available memory and the limits of
-	 * kmalloc - we don't want a kmalloc() failure of a huge value to
-	 * prevent us from finding any LUNs on this target.
+	 * plus the number of luns we are requesting.  511 was the default
+	 * value of the now removed max_report_luns parameter.
 	 */
-	length = (max_scsi_report_luns + 1) * sizeof(struct scsi_lun);
+	length = (511 + 1) * sizeof(struct scsi_lun);
+retry:
 	lun_data = kmalloc(length, GFP_KERNEL |
 			   (sdev->host->unchecked_isa_dma ? __GFP_DMA : 0));
 	if (!lun_data) {
@@ -1473,17 +1455,16 @@ static int scsi_report_lun_scan(struct scsi_target *starget, int bflags,
 	/*
 	 * Get the length from the first four bytes of lun_data.
 	 */
+	if (get_unaligned_be32(lun_data->scsi_lun) +
+	    sizeof(struct scsi_lun) > length) {
+		length = get_unaligned_be32(lun_data->scsi_lun) +
+			 sizeof(struct scsi_lun);
+		kfree(lun_data);
+		goto retry;
+	}
 	length = get_unaligned_be32(lun_data->scsi_lun);
 
 	num_luns = (length / sizeof(struct scsi_lun));
-	if (num_luns > max_scsi_report_luns) {
-		sdev_printk(KERN_WARNING, sdev,
-			    "Only %d (max_scsi_report_luns)"
-			    " of %d luns reported, try increasing"
-			    " max_scsi_report_luns.\n",
-			    max_scsi_report_luns, num_luns);
-		num_luns = max_scsi_report_luns;
-	}
 
 	SCSI_LOG_SCAN_BUS(3, sdev_printk (KERN_INFO, sdev,
 		"scsi scan: REPORT LUN scan\n"));
-- 
1.8.3.1

Re: [PATCH V6 0/3] scsi: Configure number of LUs reported by 'report-luns'

[Ewan Milne]

On Tue, 2014-12-16 at 11:01 -0500, Rob Evers wrote:
> This patch set retrieves the number of LUs available on a target
> using the report-luns command by re-sizing the returned data
> buffer and retrying report luns.
> 
> A minor bug fix is included.
> 
> scsi_mod parameter max_report_luns is no longer used and is removed.
> 
> Changes from previous posting:
> 
>  - remove exteraneous else
> 
>  - remove INITIAL_MAX_REPORT_LUNS, hardwire buffer sizing, and touch up
>    related comment
> 
> Rob Evers (3):
>   scsi: Avoid unnecessary GFP_ATOMIC allocation in scsi_report_lun_scan
>   scsi: Use set/get_unaligned_be32 in report_luns
>   scsi: retry report-luns when reported LU count requres more memory
> 
>  drivers/scsi/scsi_scan.c | 54 ++++++++++++++----------------------------------
>  1 file changed, 15 insertions(+), 39 deletions(-)
> 

Looks good.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>

Re: [PATCH V6 0/3] scsi: Configure number of LUs reported by 'report-luns'

[Christoph Hellwig]

Thanks, applied to scsi-for-3.20.