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authorJeff Mahoney <jeffm@suse.de>2012-08-18 15:20:41 -0400
committerJames Bottomley <JBottomley@Parallels.com>2012-09-14 17:59:29 +0100
commit6ed33a4a0b86da42638b5f6a0bb9f9f9aee89f60 (patch)
treeb5ff656a99557e05d63f5e2eb16852ace1e8c7a5
parent26898afd67dfd707aa291648ca731063c8333c7f (diff)
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[SCSI] st: raise device limit
The device limit of 128 tape drives was established in 2003 as a significant increase from the 8 tape drives allowed previously. We're seeing customer sites that between a large number of drives and multipath are discovering more than 128 devices and running into problems. Now that we're not stuck having to store a pointer in array and aren't limited by kmalloc failing on higher order allocs we can lift the limit to fill the entire minor range based on the number of modes. Based on the current code, that's 2^17 devices. Reviewed-by: Lee Duncan <lduncan@suse.com> Signed-off-by: Jeff Mahoney <jeffm@suse.com> Acked-by: Kai Mäkisara <kai.makisara@kolumbus.fi> Signed-off-by: James Bottomley <JBottomley@Parallels.com>
-rw-r--r--Documentation/scsi/st.txt6
-rw-r--r--drivers/scsi/st.h2
2 files changed, 3 insertions, 5 deletions
diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.txt
index 685bf35..f346abb 100644
--- a/Documentation/scsi/st.txt
+++ b/Documentation/scsi/st.txt
@@ -112,10 +112,8 @@ attempted).
MINOR NUMBERS
-The tape driver currently supports 128 drives by default. This number
-can be increased by editing st.h and recompiling the driver if
-necessary. The upper limit is 2^17 drives if 4 modes for each drive
-are used.
+The tape driver currently supports up to 2^17 drives if 4 modes for
+each drive are used.
The minor numbers consist of the following bit fields:
diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index b7a07c7..f3eee0f 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -78,7 +78,7 @@ struct st_modedef {
#define ST_MODE_SHIFT (7 - ST_NBR_MODE_BITS)
#define ST_MODE_MASK ((ST_NBR_MODES - 1) << ST_MODE_SHIFT)
-#define ST_MAX_TAPES 128
+#define ST_MAX_TAPES (1 << (20 - (ST_NBR_MODE_BITS + 1)))
#define ST_MAX_TAPE_ENTRIES (ST_MAX_TAPES << (ST_NBR_MODE_BITS + 1))
/* The status related to each partition */