Martin K. Petersen wrote:
This version fixes 64-bit modulo on 32-bit as well as inadvertent map updates when TP was disabled. Implement support for thin provisioning in scsi_debug. No actual memory de-allocation is taking place. The intent is to emulate a thinly provisioned storage device, not to be one. There are four new module options: - unmap_granularity specifies the granularity at which to track mapped blocks (specified in number of logical blocks). 2048 (1 MB) is a realistic value for disk arrays although some may have a finer granularity. - unmap_alignment specifies the first LBA which is naturally aligned on an unmap_granularity boundary. - unmap_max_desc specifies the maximum number of ranges that can be unmapped using one UNMAP command. If this is 0, only WRITE SAME is supported and UNMAP will cause a check condition. - unmap_max_blocks specifies the maximum number of blocks that can be unmapped using a single UNMAP command. Default is 0xffffffff. These parameters are reported in the new and extended block limits VPD. If unmap_granularity is specified the device is tagged as thin provisioning capable in READ CAPACITY(16). A bitmap is allocated to track whether blocks are mapped or not. A WRITE request will cause a block to be mapped. So will WRITE SAME unless the UNMAP bit is set. Blocks can be unmapped using either WRITE SAME or UNMAP. No accounting is done to track partial blocks. This means that only whole blocks will be marked free. This is how the array people tell me their firmwares work. GET LBA STATUS is also supported. This command reports whether a block is mapped or not, and how long the adjoining mapped/unmapped extent is. The block allocation bitmap can also be viewed from user space via: /sys/bus/pseudo/drivers/scsi_debug/map Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Acked-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx> While testing scsi_debug with these patches I found a problem with the Block Limits VPD page function. The length returned by the inquiry_evpd_b0() function was too short. A patch to fix that and a cosmetic change (that the form factor of scsi_debug is less than 1.8 inches) is attached. Signed-of-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
--- linux/drivers/scsi/scsi_debug.c2631mp2 2009-10-14 11:41:17.000000000 -0400 +++ linux/drivers/scsi/scsi_debug.c 2009-10-15 14:52:08.000000000 -0400 @@ -685,10 +685,12 @@ } +/* Block limits VPD page (SBC-3) */ static unsigned char vpdb0_data[] = { - /* from 4th byte */ 0,0,0,4, - 0,0,0x4,0, - 0,0,0,64, + /* from 4th byte */ 0,0,0,4, 0,0,0x4,0, 0,0,0,64, + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, + 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, }; static int inquiry_evpd_b0(unsigned char * arr) @@ -731,11 +733,14 @@ return sizeof(vpdb0_data); } +/* Block device characteristics VPD page (SBC-3) */ static int inquiry_evpd_b1(unsigned char *arr) { memset(arr, 0, 0x3c); arr[0] = 0; - arr[1] = 1; + arr[1] = 1; /* non rotating medium (e.g. solid state) */ + arr[2] = 0; + arr[3] = 5; /* less than 1.8" */ return 0x3c; }