[SCSI] st: raise device limit (6ed33a4a) · Commits · 戴 / test

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>

Documentation/scsi/st.txt

+2 −4

Original line number	Diff line number	Diff line
		@@ -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:

drivers/scsi/st.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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 */

Admin message