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[SCSI] st: expand ability to write immediate filemarks 

The st tape driver recently added the MTWEOFI ioctl, which writes
a tape filemark (EOF), like the MTWEOF ioctl, except that MTWEOFI
returns immediately. This makes certain applications, like backup
software, run much more quickly on buffered tape drives.

Since legacy applications do not know about this new MTWEOFI ioctl,
this patch adds a new ioctl option that tells the st driver to return
immediately when writing an EOF (i.e. a filemark). This new flag
is much like the existing flag that tells the st driver to perform
writes (and certain other IOs) immediately, but this new flag only
applies to writing EOFs.

This new feature is controlled via the MTSETDRVBUFFER ioctl, using
the newly-defined MT_ST_NOWAIT_EOF flag.

Use of this new feature is displayed via the sysfs tape "options"
attribute.

The st documentation was updated to mention this new flag, as well
as the problems that can occur from using it.

Signed-off-by: Lee Duncan <lduncan@suse.com>
Acked-by: Kai Makisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Lee Duncan 2012-03-01 12:41:01 -08:00 committed by James Bottomley
parent 3194eef325
commit c743e44fbb
4 changed files with 24 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/scsi/st.txt
View File

@ -390,6 +390,10 @@ MTSETDRVBUFFER
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
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
reading in variable block mode to enhance performance when
reading blocks shorter than the byte count; set this only

21
drivers/scsi/st.c
View File

@ -1106,6 +1106,12 @@ static int check_tape(struct scsi_tape *STp, struct file *filp)
STp->drv_buffer));
}
STp->drv_write_prot = ((STp->buffer)->b_data[2] & 0x80) != 0;
if (!STp->drv_buffer && STp->immediate_filemark) {
printk(KERN_WARNING
"%s: non-buffered tape: disabling writing immediate filemarks\n",
name);
STp->immediate_filemark = 0;
}
}
st_release_request(SRpnt);
SRpnt = NULL;
@ -1314,6 +1320,8 @@ static int st_flush(struct file *filp, fl_owner_t id)
memset(cmd, 0, MAX_COMMAND_SIZE);
cmd[0] = WRITE_FILEMARKS;
if (STp->immediate_filemark)
cmd[1] = 1;
cmd[4] = 1 + STp->two_fm;
SRpnt = st_do_scsi(NULL, STp, cmd, 0, DMA_NONE,
@ -2181,8 +2189,9 @@ static void st_log_options(struct scsi_tape * STp, struct st_modedef * STm, char
name, STm->defaults_for_writes, STp->omit_blklims, STp->can_partitions,
STp->scsi2_logical);
printk(KERN_INFO
"%s: sysv: %d nowait: %d sili: %d\n", name, STm->sysv, STp->immediate,
STp->sili);
"%s: sysv: %d nowait: %d sili: %d nowait_filemark: %d\n",
name, STm->sysv, STp->immediate, STp->sili,
STp->immediate_filemark);
printk(KERN_INFO "%s: debugging: %d\n",
name, debugging);
}
@ -2224,6 +2233,7 @@ static int st_set_options(struct scsi_tape *STp, long options)
STp->can_partitions = (options & MT_ST_CAN_PARTITIONS) != 0;
STp->scsi2_logical = (options & MT_ST_SCSI2LOGICAL) != 0;
STp->immediate = (options & MT_ST_NOWAIT) != 0;
STp->immediate_filemark = (options & MT_ST_NOWAIT_EOF) != 0;
STm->sysv = (options & MT_ST_SYSV) != 0;
STp->sili = (options & MT_ST_SILI) != 0;
DEB( debugging = (options & MT_ST_DEBUGGING) != 0;
@ -2255,6 +2265,8 @@ static int st_set_options(struct scsi_tape *STp, long options)
STp->scsi2_logical = value;
if ((options & MT_ST_NOWAIT) != 0)
STp->immediate = value;
if ((options & MT_ST_NOWAIT_EOF) != 0)
STp->immediate_filemark = value;
if ((options & MT_ST_SYSV) != 0)
STm->sysv = value;
if ((options & MT_ST_SILI) != 0)
@ -2714,7 +2726,8 @@ static int st_int_ioctl(struct scsi_tape *STp, unsigned int cmd_in, unsigned lon
cmd[0] = WRITE_FILEMARKS;
if (cmd_in == MTWSM)
cmd[1] = 2;
if (cmd_in == MTWEOFI)
if (cmd_in == MTWEOFI ||
(cmd_in == MTWEOF && STp->immediate_filemark))
cmd[1] |= 1;
cmd[2] = (arg >> 16);
cmd[3] = (arg >> 8);
@ -4093,6 +4106,7 @@ static int st_probe(struct device *dev)
tpnt->scsi2_logical = ST_SCSI2LOGICAL;
tpnt->sili = ST_SILI;
tpnt->immediate = ST_NOWAIT;
tpnt->immediate_filemark = 0;
tpnt->default_drvbuffer = 0xff; /* No forced buffering */
tpnt->partition = 0;
tpnt->new_partition = 0;
@ -4478,6 +4492,7 @@ st_options_show(struct device *dev, struct device_attribute *attr, char *buf)
options |= STp->scsi2_logical ? MT_ST_SCSI2LOGICAL : 0;
options |= STm->sysv ? MT_ST_SYSV : 0;
options |= STp->immediate ? MT_ST_NOWAIT : 0;
options |= STp->immediate_filemark ? MT_ST_NOWAIT_EOF : 0;
options |= STp->sili ? MT_ST_SILI : 0;
l = snprintf(buf, PAGE_SIZE, "0x%08x\n", options);

1
drivers/scsi/st.h
View File

@ -120,6 +120,7 @@ struct scsi_tape {
unsigned char c_algo; /* compression algorithm */
unsigned char pos_unknown; /* after reset position unknown */
unsigned char sili; /* use SILI when reading in variable b mode */
unsigned char immediate_filemark; /* write filemark immediately */
int tape_type;
int long_timeout; /* timeout for commands known to take long time */

1
include/linux/mtio.h
View File

@ -194,6 +194,7 @@ struct mtpos {
#define MT_ST_SYSV 0x1000
#define MT_ST_NOWAIT 0x2000
#define MT_ST_SILI 0x4000
#define MT_ST_NOWAIT_EOF 0x8000
/* The mode parameters to be controlled. Parameter chosen with bits 20-28 */
#define MT_ST_CLEAR_DEFAULT 0xfffff