From 24d720b726c1a85f1962831ac30ad4d2ef8276b1 Mon Sep 17 00:00:00 2001 From: Luben Tuikov Date: Fri, 22 Oct 2010 21:24:36 -0700 Subject: [PATCH] [SCSI] Retrieve the Caching mode page MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Some kernel transport drivers unconditionally disable retrieval of the Caching mode page. One such for example is the BBB/CBI transport over USB.  Such a restraint is too harsh as some devices do support the Caching mode page. Unconditionally enabling the retrieval of this mode page over those transports at their transport code level may result in some devices failing and becoming unusable. This patch implements a method of retrieving the Caching mode page without unconditionally enabling it in the transports which unconditionally disable it. The idea is to ask for all supported pages, page code 0x3F, and then search for the Caching mode page in the mode parameter data returned. The sd driver already asks for all the mode pages supported by the attached device by setting the page code to 0x3F in order to find out if the media is write protected by reading the WP bit in the Device Specific Parameter field. It then attempts to retrieve only the Caching mode page by setting the page code to 8 and actually attempting to retrieve it if and only if the transport allows it. The method implemented here is that if the transport doesn't allow retrieval of the Caching mode page and the device is not RBC, then we ask for all pages supported by setting the page code to 0x3F (similarly to how the WP bit is retrieved above), and then we search for the Caching mode page in the mode parameter data returned. With this patch, devices over SATA, report this (no change): Oct 22 18:45:58 localhost kernel: sd 0:0:0:0: [sda] 976773168 512-byte logical blocks: (500 GB/465 GiB) Oct 22 18:45:58 localhost kernel: sd 0:0:0:0: Attached scsi generic sg0 type 0 Oct 22 18:45:58 localhost kernel: sd 0:0:0:0: [sda] Write Protect is off Oct 22 18:45:58 localhost kernel: sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00 Oct 22 18:45:58 localhost kernel: sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA Smart devices report their Caching mode page. This is a change where we'd previously see the kernel making assumption about the device's cache being write-through: Oct 22 18:45:58 localhost kernel: sd 6:0:0:0: Attached scsi generic sg2 type 0 Oct 22 18:45:58 localhost kernel: sd 6:0:0:0: [sdb] 610472646 4096-byte logical blocks: (2.50 TB/2.27 TiB) Oct 22 18:45:58 localhost kernel: sd 6:0:0:0: [sdb] Write Protect is off Oct 22 18:45:58 localhost kernel: sd 6:0:0:0: [sdb] Mode Sense: 47 00 10 08 Oct 22 18:45:58 localhost kernel: sd 6:0:0:0: [sdb] Write cache: enabled, read cache: enabled, supports DPO and FUA And "dumb" devices over BBB, are correctly shown not to support reporting the Caching mode page: Oct 22 18:49:06 localhost kernel: sd 7:0:0:0: [sdc] 15663104 512-byte logical blocks: (8.01 GB/7.46 GiB) Oct 22 18:49:06 localhost kernel: sd 7:0:0:0: [sdc] Write Protect is off Oct 22 18:49:06 localhost kernel: sd 7:0:0:0: [sdc] Mode Sense: 23 00 00 00 Oct 22 18:49:06 localhost kernel: sd 7:0:0:0: [sdc] No Caching mode page present Oct 22 18:49:06 localhost kernel: sd 7:0:0:0: [sdc] Assuming drive cache: write through Signed-off-by: Luben Tuikov Signed-off-by: James Bottomley --- drivers/scsi/sd.c | 63 +++++++++++++++++++++++++++++++++++------------ 1 file changed, 47 insertions(+), 16 deletions(-) diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 26f9d54a9c92..d8e2caf9f468 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1915,10 +1915,14 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer) int old_rcd = sdkp->RCD; int old_dpofua = sdkp->DPOFUA; - if (sdp->skip_ms_page_8) - goto defaults; - - if (sdp->type == TYPE_RBC) { + if (sdp->skip_ms_page_8) { + if (sdp->type == TYPE_RBC) + goto defaults; + else { + modepage = 0x3F; + dbd = 0; + } + } else if (sdp->type == TYPE_RBC) { modepage = 6; dbd = 8; } else { @@ -1946,13 +1950,11 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer) */ if (len < 3) goto bad_sense; - if (len > 20) - len = 20; - - /* Take headers and block descriptors into account */ - len += data.header_length + data.block_descriptor_length; - if (len > SD_BUF_SIZE) - goto bad_sense; + else if (len > SD_BUF_SIZE) { + sd_printk(KERN_NOTICE, sdkp, "Truncating mode parameter " + "data from %d to %d bytes\n", len, SD_BUF_SIZE); + len = SD_BUF_SIZE; + } /* Get the data */ res = sd_do_mode_sense(sdp, dbd, modepage, buffer, len, &data, &sshdr); @@ -1960,16 +1962,45 @@ sd_read_cache_type(struct scsi_disk *sdkp, unsigned char *buffer) if (scsi_status_is_good(res)) { int offset = data.header_length + data.block_descriptor_length; - if (offset >= SD_BUF_SIZE - 2) { - sd_printk(KERN_ERR, sdkp, "Malformed MODE SENSE response\n"); - goto defaults; + while (offset < len) { + u8 page_code = buffer[offset] & 0x3F; + u8 spf = buffer[offset] & 0x40; + + if (page_code == 8 || page_code == 6) { + /* We're interested only in the first 3 bytes. + */ + if (len - offset <= 2) { + sd_printk(KERN_ERR, sdkp, "Incomplete " + "mode parameter data\n"); + goto defaults; + } else { + modepage = page_code; + goto Page_found; + } + } else { + /* Go to the next page */ + if (spf && len - offset > 3) + offset += 4 + (buffer[offset+2] << 8) + + buffer[offset+3]; + else if (!spf && len - offset > 1) + offset += 2 + buffer[offset+1]; + else { + sd_printk(KERN_ERR, sdkp, "Incomplete " + "mode parameter data\n"); + goto defaults; + } + } } - if ((buffer[offset] & 0x3f) != modepage) { + if (modepage == 0x3F) { + sd_printk(KERN_ERR, sdkp, "No Caching mode page " + "present\n"); + goto defaults; + } else if ((buffer[offset] & 0x3f) != modepage) { sd_printk(KERN_ERR, sdkp, "Got wrong page\n"); goto defaults; } - + Page_found: if (modepage == 8) { sdkp->WCE = ((buffer[offset + 2] & 0x04) != 0); sdkp->RCD = ((buffer[offset + 2] & 0x01) != 0); -- 2.20.1