diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/scsi/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/scsi/scsi-parameters.rst | 4 | ||||
| -rw-r--r-- | Documentation/scsi/st.rst (renamed from Documentation/scsi/st.txt) | 301 |
3 files changed, 194 insertions, 112 deletions
diff --git a/Documentation/scsi/index.rst b/Documentation/scsi/index.rst index ff98919faed7..0cc2cfca7474 100644 --- a/Documentation/scsi/index.rst +++ b/Documentation/scsi/index.rst @@ -40,5 +40,6 @@ Linux SCSI Subsystem scsi sd-parameters smartpqi + st scsi_transport_srp/figures diff --git a/Documentation/scsi/scsi-parameters.rst b/Documentation/scsi/scsi-parameters.rst index 0c4bbb1aee94..9aba897c97ac 100644 --- a/Documentation/scsi/scsi-parameters.rst +++ b/Documentation/scsi/scsi-parameters.rst @@ -73,7 +73,7 @@ parameters may be changed at runtime by the command osst= [HW,SCSI] SCSI Tape Driver Format: <buffer_size>,<write_threshold> - See also Documentation/scsi/st.txt. + See also Documentation/scsi/st.rst. scsi_debug_*= [SCSI] See drivers/scsi/scsi_debug.c. @@ -105,7 +105,7 @@ parameters may be changed at runtime by the command See header of drivers/scsi/sim710.c. st= [HW,SCSI] SCSI tape parameters (buffers, etc.) - See Documentation/scsi/st.txt. + See Documentation/scsi/st.rst. wd33c93= [HW,SCSI] See header of drivers/scsi/wd33c93.c. diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.rst index ec0acf6acccd..d3b28c28d74c 100644 --- a/Documentation/scsi/st.txt +++ b/Documentation/scsi/st.rst @@ -1,3 +1,9 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +The SCSI Tape Driver +==================== + This file contains brief information about the SCSI tape driver. The driver is currently maintained by Kai Mäkisara (email Kai.Makisara@kolumbus.fi) @@ -5,7 +11,8 @@ Kai.Makisara@kolumbus.fi) Last modified: Tue Feb 9 21:54:16 2016 by kai.makisara -BASICS +Basics +====== The driver is generic, i.e., it does not contain any code tailored to any specific tape drive. The tape parameters can be specified with @@ -110,15 +117,17 @@ tape in the drive (commands trying to write something return error if attempted). -MINOR NUMBERS +Minor Numbers +============= 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: +The minor numbers consist of the following bit fields:: + + dev_upper non-rew mode dev-lower + 20 - 8 7 6 5 4 0 -dev_upper non-rew mode dev-lower - 20 - 8 7 6 5 4 0 The non-rewind bit is always bit 7 (the uppermost bit in the lowermost byte). The bits defining the mode are below the non-rewind bit. The remaining bits define the tape device number. This numbering is @@ -126,7 +135,8 @@ backward compatible with the numbering used when the minor number was only 8 bits wide. -SYSFS SUPPORT +Sysfs Support +============= The driver creates the directory /sys/class/scsi_tape and populates it with directories corresponding to the existing tape devices. There are autorewind @@ -148,10 +158,11 @@ bit definitions are the same as those used with MTSETDRVBUFFER in setting the options. A link named 'tape' is made from the SCSI device directory to the class -directory corresponding to the mode 0 auto-rewind device (e.g., st0). +directory corresponding to the mode 0 auto-rewind device (e.g., st0). -SYSFS AND STATISTICS FOR TAPE DEVICES +Sysfs and Statistics for Tape Devices +===================================== The st driver maintains statistics for tape drives inside the sysfs filesystem. The following method can be used to locate the statistics that are @@ -160,10 +171,10 @@ available (assuming that sysfs is mounted at /sys): 1. Use opendir(3) on the directory /sys/class/scsi_tape 2. Use readdir(3) to read the directory contents 3. Use regcomp(3)/regexec(3) to match directory entries to the extended - regular expression "^st[0-9]+$" + regular expression "^st[0-9]+$" 4. Access the statistics from the /sys/class/scsi_tape/<match>/stats - directory (where <match> is a directory entry from /sys/class/scsi_tape - that matched the extended regular expression) + directory (where <match> is a directory entry from /sys/class/scsi_tape + that matched the extended regular expression) The reason for using this approach is that all the character devices pointing to the same tape drive use the same statistics. That means @@ -171,29 +182,41 @@ that st0 would have the same statistics as nst0. The directory contains the following statistics files: -1. in_flight - The number of I/Os currently outstanding to this device. -2. io_ns - The amount of time spent waiting (in nanoseconds) for all I/O +1. in_flight + - The number of I/Os currently outstanding to this device. +2. io_ns + - The amount of time spent waiting (in nanoseconds) for all I/O to complete (including read and write). This includes tape movement commands such as seeking between file or set marks and implicit tape movement such as when rewind on close tape devices are used. -3. other_cnt - The number of I/Os issued to the tape drive other than read or +3. other_cnt + - The number of I/Os issued to the tape drive other than read or write commands. The time taken to complete these commands uses the following calculation io_ms-read_ms-write_ms. -4. read_byte_cnt - The number of bytes read from the tape drive. -5. read_cnt - The number of read requests issued to the tape drive. -6. read_ns - The amount of time (in nanoseconds) spent waiting for read +4. read_byte_cnt + - The number of bytes read from the tape drive. +5. read_cnt + - The number of read requests issued to the tape drive. +6. read_ns + - The amount of time (in nanoseconds) spent waiting for read requests to complete. -7. write_byte_cnt - The number of bytes written to the tape drive. -8. write_cnt - The number of write requests issued to the tape drive. -9. write_ns - The amount of time (in nanoseconds) spent waiting for write +7. write_byte_cnt + - The number of bytes written to the tape drive. +8. write_cnt + - The number of write requests issued to the tape drive. +9. write_ns + - The amount of time (in nanoseconds) spent waiting for write requests to complete. -10. resid_cnt - The number of times during a read or write we found +10. resid_cnt + - The number of times during a read or write we found the residual amount to be non-zero. This should mean that a program is issuing a read larger thean the block size on tape. For write not all data made it to tape. -Note: The in_flight value is incremented when an I/O starts the I/O -itself is not added to the statistics until it completes. +.. Note:: + + The in_flight value is incremented when an I/O starts the I/O + itself is not added to the statistics until it completes. The total of read_cnt, write_cnt, and other_cnt may not total to the same value as iodone_cnt at the device level. The tape statistics only count @@ -210,7 +233,8 @@ The value of in_flight is 0 when there are no I/Os outstanding that are issued by the st driver. Tape statistics do not take into account any I/O performed via the sg device. -BSD AND SYS V SEMANTICS +BSD and Sys V Semantics +======================= The user can choose between these two behaviours of the tape driver by defining the value of the symbol ST_SYSV. The semantics differ when a @@ -221,13 +245,15 @@ filemark unless the filemark has just been crossed. The default is BSD semantics. -BUFFERING +Buffering +========= The driver tries to do transfers directly to/from user space. If this is not possible, a driver buffer allocated at run-time is used. If direct i/o is not possible for the whole transfer, the driver buffer is used (i.e., bounce buffers for individual pages are not used). Direct i/o can be impossible because of several reasons, e.g.: + - one or more pages are at addresses not reachable by the HBA - the number of pages in the transfer exceeds the number of scatter/gather segments permitted by the HBA @@ -269,28 +295,30 @@ in the physical memory) are used if contiguous buffers can't be allocated. To support all SCSI adapters (including those not supporting scatter/gather), buffer allocation is using the following three kinds of chunks: + 1. The initial segment that is used for all SCSI adapters including -those not supporting scatter/gather. The size of this buffer will be -(PAGE_SIZE << ST_FIRST_ORDER) bytes if the system can give a chunk of -this size (and it is not larger than the buffer size specified by -ST_BUFFER_BLOCKS). If this size is not available, the driver halves -the size and tries again until the size of one page. The default -settings in st_options.h make the driver to try to allocate all of the -buffer as one chunk. + those not supporting scatter/gather. The size of this buffer will be + (PAGE_SIZE << ST_FIRST_ORDER) bytes if the system can give a chunk of + this size (and it is not larger than the buffer size specified by + ST_BUFFER_BLOCKS). If this size is not available, the driver halves + the size and tries again until the size of one page. The default + settings in st_options.h make the driver to try to allocate all of the + buffer as one chunk. 2. The scatter/gather segments to fill the specified buffer size are -allocated so that as many segments as possible are used but the number -of segments does not exceed ST_FIRST_SG. + allocated so that as many segments as possible are used but the number + of segments does not exceed ST_FIRST_SG. 3. The remaining segments between ST_MAX_SG (or the module parameter -max_sg_segs) and the number of segments used in phases 1 and 2 -are used to extend the buffer at run-time if this is necessary. The -number of scatter/gather segments allowed for the SCSI adapter is not -exceeded if it is smaller than the maximum number of scatter/gather -segments specified. If the maximum number allowed for the SCSI adapter -is smaller than the number of segments used in phases 1 and 2, -extending the buffer will always fail. + max_sg_segs) and the number of segments used in phases 1 and 2 + are used to extend the buffer at run-time if this is necessary. The + number of scatter/gather segments allowed for the SCSI adapter is not + exceeded if it is smaller than the maximum number of scatter/gather + segments specified. If the maximum number allowed for the SCSI adapter + is smaller than the number of segments used in phases 1 and 2, + extending the buffer will always fail. -EOM BEHAVIOUR WHEN WRITING +EOM Behaviour When Writing +========================== When the end of medium early warning is encountered, the current write is finished and the number of bytes is returned. The next write @@ -300,12 +328,13 @@ bytes is returned. After this, -1 and the number of bytes are alternately returned until the physical end of medium (or some other error) is encountered. - -MODULE PARAMETERS +Module Parameters +================= The buffer size, write threshold, and the maximum number of allocated buffers are configurable when the driver is loaded as a module. The keywords are: +========================== =========================================== buffer_kbs=xxx the buffer size for fixed block mode is set to xxx kilobytes write_threshold_kbs=xxx the write threshold in kilobytes set to xxx @@ -313,12 +342,14 @@ max_sg_segs=xxx the maximum number of scatter/gather segments try_direct_io=x try direct transfer between user buffer and tape drive if this is non-zero +========================== =========================================== Note that if the buffer size is changed but the write threshold is not set, the write threshold is set to the new buffer size - 2 kB. -BOOT TIME CONFIGURATION +Boot Time Configuration +======================= If the driver is compiled into the kernel, the same parameters can be also set using, e.g., the LILO command line. The preferred syntax is @@ -332,21 +363,23 @@ versions is supported. The same keywords can be used as when loading the driver as module. If several parameters are set, the keyword-value pairs are separated with a comma (no spaces allowed). A colon can be used instead of the equal mark. The definition is prepended by the -string st=. Here is an example: +string st=. Here is an example:: st=buffer_kbs:64,write_threshold_kbs:60 -The following syntax used by the old kernel versions is also supported: +The following syntax used by the old kernel versions is also supported:: st=aa[,bb[,dd]] -where - aa is the buffer size for fixed block mode in 1024 byte units - bb is the write threshold in 1024 byte units - dd is the maximum number of scatter/gather segments +where: + - aa is the buffer size for fixed block mode in 1024 byte units + - bb is the write threshold in 1024 byte units + - dd is the maximum number of scatter/gather segments -IOCTLS + +IOCTLs +====== The tape is positioned and the drive parameters are set with ioctls defined in mtio.h The tape control program 'mt' uses these ioctls. Try @@ -359,55 +392,80 @@ The supported ioctls are: The following use the structure mtop: -MTFSF Space forward over count filemarks. Tape positioned after filemark. -MTFSFM As above but tape positioned before filemark. -MTBSF Space backward over count filemarks. Tape positioned before +MTFSF + Space forward over count filemarks. Tape positioned after filemark. +MTFSFM + As above but tape positioned before filemark. +MTBSF + Space backward over count filemarks. Tape positioned before filemark. -MTBSFM As above but ape positioned after filemark. -MTFSR Space forward over count records. -MTBSR Space backward over count records. -MTFSS Space forward over count setmarks. -MTBSS Space backward over count setmarks. -MTWEOF Write count filemarks. -MTWEOFI Write count filemarks with immediate bit set (i.e., does not +MTBSFM + As above but ape positioned after filemark. +MTFSR + Space forward over count records. +MTBSR + Space backward over count records. +MTFSS + Space forward over count setmarks. +MTBSS + Space backward over count setmarks. +MTWEOF + Write count filemarks. +MTWEOFI + Write count filemarks with immediate bit set (i.e., does not wait until data is on tape) -MTWSM Write count setmarks. -MTREW Rewind tape. -MTOFFL Set device off line (often rewind plus eject). -MTNOP Do nothing except flush the buffers. -MTRETEN Re-tension tape. -MTEOM Space to end of recorded data. -MTERASE Erase tape. If the argument is zero, the short erase command +MTWSM + Write count setmarks. +MTREW + Rewind tape. +MTOFFL + Set device off line (often rewind plus eject). +MTNOP + Do nothing except flush the buffers. +MTRETEN + Re-tension tape. +MTEOM + Space to end of recorded data. +MTERASE + Erase tape. If the argument is zero, the short erase command is used. The long erase command is used with all other values of the argument. -MTSEEK Seek to tape block count. Uses Tandberg-compatible seek (QFA) +MTSEEK + Seek to tape block count. Uses Tandberg-compatible seek (QFA) for SCSI-1 drives and SCSI-2 seek for SCSI-2 drives. The file and block numbers in the status are not valid after a seek. -MTSETBLK Set the drive block size. Setting to zero sets the drive into +MTSETBLK + Set the drive block size. Setting to zero sets the drive into variable block mode (if applicable). -MTSETDENSITY Sets the drive density code to arg. See drive +MTSETDENSITY + Sets the drive density code to arg. See drive documentation for available codes. -MTLOCK and MTUNLOCK Explicitly lock/unlock the tape drive door. -MTLOAD and MTUNLOAD Explicitly load and unload the tape. If the +MTLOCK and MTUNLOCK + Explicitly lock/unlock the tape drive door. +MTLOAD and MTUNLOAD + Explicitly load and unload the tape. If the command argument x is between MT_ST_HPLOADER_OFFSET + 1 and MT_ST_HPLOADER_OFFSET + 6, the number x is used sent to the drive with the command and it selects the tape slot to use of HP C1553A changer. -MTCOMPRESSION Sets compressing or uncompressing drive mode using the +MTCOMPRESSION + Sets compressing or uncompressing drive mode using the SCSI mode page 15. Note that some drives other methods for control of compression. Some drives (like the Exabytes) use density codes for compression control. Some drives use another mode page but this page has not been implemented in the driver. Some drives without compression capability will accept any compression mode without error. -MTSETPART Moves the tape to the partition given by the argument at the +MTSETPART + Moves the tape to the partition given by the argument at the next tape operation. The block at which the tape is positioned is the block where the tape was previously positioned in the new active partition unless the next tape operation is MTSEEK. In this case the tape is moved directly to the block specified by MTSEEK. MTSETPART is inactive unless MT_ST_CAN_PARTITIONS set. -MTMKPART Formats the tape with one partition (argument zero) or two +MTMKPART + Formats the tape with one partition (argument zero) or two partitions (argument non-zero). If the argument is positive, it specifies the size of partition 1 in megabytes. For DDS drives and several early drives this is the physically first @@ -422,64 +480,81 @@ MTSETDRVBUFFER with mask MT_SET_OPTIONS, the low order bits are used as argument. This command is only allowed for the superuser (root). The subcommands are: - 0 + + * 0 The drive buffer option is set to the argument. Zero means no buffering. - MT_ST_BOOLEANS + * MT_ST_BOOLEANS Sets the buffering options. The bits are the new states (enabled/disabled) the following options (in the parenthesis is specified whether the option is global or can be specified differently for each mode): - MT_ST_BUFFER_WRITES write buffering (mode) - MT_ST_ASYNC_WRITES asynchronous writes (mode) - MT_ST_READ_AHEAD read ahead (mode) - MT_ST_TWO_FM writing of two filemarks (global) - MT_ST_FAST_EOM using the SCSI spacing to EOD (global) - MT_ST_AUTO_LOCK automatic locking of the drive door (global) - MT_ST_DEF_WRITES the defaults are meant only for writes (mode) - MT_ST_CAN_BSR backspacing over more than one records can + + MT_ST_BUFFER_WRITES + write buffering (mode) + MT_ST_ASYNC_WRITES + asynchronous writes (mode) + MT_ST_READ_AHEAD + read ahead (mode) + MT_ST_TWO_FM + writing of two filemarks (global) + MT_ST_FAST_EOM + using the SCSI spacing to EOD (global) + MT_ST_AUTO_LOCK + automatic locking of the drive door (global) + MT_ST_DEF_WRITES + the defaults are meant only for writes (mode) + MT_ST_CAN_BSR + backspacing over more than one records can be used for repositioning the tape (global) - MT_ST_NO_BLKLIMS the driver does not ask the block limits + MT_ST_NO_BLKLIMS + the driver does not ask the block limits from the drive (block size can be changed only to variable) (global) - MT_ST_CAN_PARTITIONS enables support for partitioned + MT_ST_CAN_PARTITIONS + enables support for partitioned tapes (global) - MT_ST_SCSI2LOGICAL the logical block number is used in + MT_ST_SCSI2LOGICAL + the logical block number is used in the MTSEEK and MTIOCPOS for SCSI-2 drives instead of the device dependent address. It is recommended to set this flag unless there are tapes using the device dependent (from the old times) (global) - MT_ST_SYSV sets the SYSV semantics (mode) - MT_ST_NOWAIT enables immediate mode (i.e., don't wait for + MT_ST_SYSV + sets the SYSV semantics (mode) + MT_ST_NOWAIT + enables immediate mode (i.e., don't wait for the command to finish) for some commands (e.g., rewind) - MT_ST_NOWAIT_EOF enables immediate filemark mode (i.e. when + MT_ST_NOWAIT_EOF + enables immediate filemark mode (i.e. when writing a filemark, don't wait for it to complete). Please see the BASICS note about MTWEOFI with respect to the possible dangers of writing immediate filemarks. - MT_ST_SILI enables setting the SILI bit in SCSI commands when + MT_ST_SILI + enables setting the SILI bit in SCSI commands when reading in variable block mode to enhance performance when reading blocks shorter than the byte count; set this only if you are sure that the drive supports SILI and the HBA correctly returns transfer residuals - MT_ST_DEBUGGING debugging (global; debugging must be + MT_ST_DEBUGGING + debugging (global; debugging must be compiled into the driver) - MT_ST_SETBOOLEANS - MT_ST_CLEARBOOLEANS + + * MT_ST_SETBOOLEANS, MT_ST_CLEARBOOLEANS Sets or clears the option bits. - MT_ST_WRITE_THRESHOLD + * MT_ST_WRITE_THRESHOLD Sets the write threshold for this device to kilobytes specified by the lowest bits. - MT_ST_DEF_BLKSIZE + * MT_ST_DEF_BLKSIZE Defines the default block size set automatically. Value 0xffffff means that the default is not used any more. - MT_ST_DEF_DENSITY - MT_ST_DEF_DRVBUFFER + * MT_ST_DEF_DENSITY, MT_ST_DEF_DRVBUFFER Used to set or clear the density (8 bits), and drive buffer state (3 bits). If the value is MT_ST_CLEAR_DEFAULT (0xfffff) the default will not be used any more. Otherwise the lowermost bits of the value contain the new value of the parameter. - MT_ST_DEF_COMPRESSION + * MT_ST_DEF_COMPRESSION The compression default will not be used if the value of the lowermost byte is 0xff. Otherwise the lowermost bit contains the new default. If the bits 8-15 are set to a @@ -487,17 +562,17 @@ MTSETDRVBUFFER used as the compression algorithm. The value MT_ST_CLEAR_DEFAULT can be used to clear the compression default. - MT_ST_SET_TIMEOUT + * MT_ST_SET_TIMEOUT Set the normal timeout in seconds for this device. The default is 900 seconds (15 minutes). The timeout should be long enough for the retries done by the device while reading/writing. - MT_ST_SET_LONG_TIMEOUT + * MT_ST_SET_LONG_TIMEOUT Set the long timeout that is used for operations that are known to take a long time. The default is 14000 seconds (3.9 hours). For erase this value is further multiplied by eight. - MT_ST_SET_CLN + * MT_ST_SET_CLN Set the cleaning request interpretation parameters using the lowest 24 bits of the argument. The driver can set the generic status bit GMT_CLN if a cleaning request bit pattern @@ -506,7 +581,7 @@ MTSETDRVBUFFER cleaning. The bits are device-dependent. The driver is given the number of the sense data byte (the lowest eight bits of the argument; must be >= 18 (values 1 - 17 - reserved) and <= the maximum requested sense data sixe), + reserved) and <= the maximum requested sense data sixe), a mask to select the relevant bits (the bits 9-16), and the bit pattern (bits 17-23). If the bit pattern is zero, one or more bits under the mask indicate cleaning request. If @@ -518,12 +593,16 @@ MTSETDRVBUFFER MT_ST_SET_CLN.) The following ioctl uses the structure mtpos: -MTIOCPOS Reads the current position from the drive. Uses + +MTIOCPOS + Reads the current position from the drive. Uses Tandberg-compatible QFA for SCSI-1 drives and the SCSI-2 command for the SCSI-2 drives. The following ioctl uses the structure mtget to return the status: -MTIOCGET Returns some status information. + +MTIOCGET + Returns some status information. The file number and block number within file are returned. The block is -1 when it can't be determined (e.g., after MTBSF). The drive type is either MTISSCSI1 or MTISSCSI2. @@ -537,7 +616,8 @@ MTIOCGET Returns some status information. end of recorded data or end of tape. GMT_EOT means end of tape. -MISCELLANEOUS COMPILE OPTIONS +Miscellaneous Compile Options +============================= The recovered write errors are considered fatal if ST_RECOVERED_WRITE_FATAL is defined. @@ -568,7 +648,8 @@ time or the MT_ST_CAN_BSR bit is set for the drive with an ioctl. user does not request data that far.) -DEBUGGING HINTS +Debugging Hints +=============== Debugging code is now compiled in by default but debugging is turned off with the kernel module parameter debug_flag defaulting to 0. Debugging |