scsi: retry report-luns when reported LU count requres more memory

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>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 11 insertions, 30 deletions

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index b7948d20c23b..0deb385ad4d6 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);
@@ -1407,15 +1393,11 @@ 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) {
@@ -1481,17 +1463,16 @@ 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"));