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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>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.