3.18-stable review patch. If anyone has any objections, please let me know.
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From: Ivan Mironov mironov.ivan@gmail.com
commit 44759979a49bfd2d20d789add7fa81a21eb1a4ab upstream.
Changing of caching mode via /sys/devices/.../scsi_disk/.../cache_type may fail if device responds to MODE SENSE command with DPOFUA flag set, and then checks this flag to be not set on MODE SELECT command.
In this scenario, when trying to change cache_type, write always fails:
# echo "none" >cache_type bash: echo: write error: Invalid argument
And following appears in dmesg:
[13007.865745] sd 1:0:1:0: [sda] Sense Key : Illegal Request [current] [13007.865753] sd 1:0:1:0: [sda] Add. Sense: Invalid field in parameter list
From SBC-4 r15, 6.5.1 "Mode pages overview", description of DEVICE-SPECIFIC
PARAMETER field in the mode parameter header: ... The write protect (WP) bit for mode data sent with a MODE SELECT command shall be ignored by the device server. ... The DPOFUA bit is reserved for mode data sent with a MODE SELECT command. ...
The remaining bits in the DEVICE-SPECIFIC PARAMETER byte are also reserved and shall be set to zero.
[mkp: shuffled commentary to commit description]
Cc: stable@vger.kernel.org Signed-off-by: Ivan Mironov mironov.ivan@gmail.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/scsi/sd.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -205,6 +205,12 @@ cache_type_store(struct device *dev, str buffer_data[2] |= wce << 2 | rcd; sp = buffer_data[0] & 0x80 ? 1 : 0;
+ /* + * Ensure WP, DPOFUA, and RESERVED fields are cleared in + * received mode parameter buffer before doing MODE SELECT. + */ + data.device_specific = 0; + if (scsi_mode_select(sdp, 1, sp, 8, buffer_data, len, SD_TIMEOUT, SD_MAX_RETRIES, &data, &sshdr)) { if (scsi_sense_valid(&sshdr))