Re: [Scst-devel] system crash

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my understanding, not 100% right.

fileio is more flexible, it can export any regular file and block device
as a scsi disk. so it can be very useful for stuff like lvm, evms, ...

fileio can introduce file system cache and lead to some performance gain
and data inconsistency point; 

diskio is like a bridge, so less overhead to export a scsi disk compared
with fileio. it should be useful as a FC-SCSI bridge.

for other device handlers, frankly i do not know. since i do not have
such devices at all.

i only know a little about scsi_fileio.

Ming

On Fri, 2006-05-19 at 11:36 -0500, Brad Johnson wrote:
> What are the advantages/disadvantages of using fileio instead of diskio?
> Also, how does the raid device handler work?
> 
> ...Brad
> 
> 
> On Fri, 2006-05-19 at 12:29 -0400, Ming Zhang wrote:
> > thx for the info. i never run diskio so i am not aware of its stability.
> > maybe Vlad has better idea on this.
> > 
> > Ming
> > 
> > 
> > On Fri, 2006-05-19 at 11:25 -0500, Brad Johnson wrote:
> > > I tried it again, this time using the fileio handler (I exported an
> > > entire device /dev/sda1).
> > > This time I did not have any problems. From the initiator system I ran
> > > an entire bonnie disk I/O test run without failure.
> > > 
> > > ...Brad
> > > 
> > > 
> > > On Thu, 2006-05-18 at 18:38 -0400, Ming Zhang wrote:
> > > > 1) can u try latest code from scst cvs
> > > > 
> > > > 2) can u try to export it via scst_fileio module? see if oops in same
> > > > place.
> > > > 
> > > > ming
> > > > 
> > > > 
> > > > 
> > > > 
> > > > On Thu, 2006-05-18 at 17:20 -0500, Brad Johnson wrote:
> > > > > The system running scst crashes when doing I/O to target from remote
> > > > > system.
> > > > > 
> > > > > Here is my setup:
> > > > > My target system has 2 Intel Xeon processors (3.2 MHz) and 1 GB RAM.
> > > > > It is running Linux 2.6.15.7.
> > > > > It has scst-0.9.4 and qla2x00-target-26-0.9.3.8 installed.
> > > > > It has a Qlogic 2312 HBA connected to a switch. This is my FC target
> > > > > host. (My FC Initiator is another x86 system with a Qlogic HBA also
> > > > > connected to the switch.)
> > > > > For back-end devices it has an LSI FC949X HBA connected to a Hitachi
> > > > > Fibre-channel drive.
> > > > > 
> > > > > Here is my start script:
> > > > > --------------------------------------------------------
> > > > > modprobe -v qla2x00tgt
> > > > > modprobe -v scst_disk
> > > > > echo "add 2:0:3:0 0" >/proc/scsi_tgt/groups/Default/devices
> > > > > echo "1" >/sys/class/scsi_host/host5/target_mode_enabled
> > > > > --------------------------------------------------------
> > > > > 
> > > > > In the script, 2:0:3:0 refers to my Hitachi drive, host5 refers to my
> > > > > Qlogic target-mode port. Everything starts successfully (including
> > > > > scsi_tgt module since it is a dependency of scst_disk).
> > > > > 
> > > > > >From my initiator system I see the one drive I have exposed. I
> > > > > successfully partition that drive and do mkfs. At this point everything
> > > > > is still fine. I then mount the file system and copy a big file to it.
> > > > > The copy seems to work fine but at some point shortly after that my
> > > > > target system crashes. There is no oops output to the system log. So I
> > > > > did it again with a remote kgdb attached. Here is the gdb output:
> > > > > 
> > > > > 
> > > > > Program received signal SIGILL, Illegal instruction.
> > > > > __free_pages (page=0xc190a22c, order=0) at mm/page_alloc.c:1055
> > > > > 1055            if (put_page_testzero(page)) {
> > > > > (gdb) bt
> > > > > #0  __free_pages (page=0xc190a22c, order=0) at mm/page_alloc.c:1055
> > > > > #1  0xf8d61efd in scst_release_space (cmd=0xf40a4e58)
> > > > >     at /root/mid-level/scst-0.9.4/src/scst_lib.c:1430
> > > > > #2  0xf8d60b2a in scst_free_cmd (cmd=0xf40a4e58, check_retry=1)
> > > > >     at /root/mid-level/scst-0.9.4/src/scst_lib.c:956
> > > > > #3  0xf8d599ee in scst_finish_cmd (cmd=0xf40a4e58)
> > > > >     at /root/mid-level/scst-0.9.4/src/scst_targ.c:2212
> > > > > #4  0xf8d5a7df in __scst_process_active_cmd (cmd=0xf40a4e58,
> > > > >     context=<value optimized out>, pflags=0xc046cfb8,
> > > > >     left_locked=<value optimized out>)
> > > > >     at /root/mid-level/scst-0.9.4/src/scst_targ.c:2461
> > > > > #5  0xf8d5aa81 in scst_do_job_active (active_cmd_list=0xf8d756d0,
> > > > >     pflags=0xc046cfb8, context=268435457)
> > > > >     at /root/mid-level/scst-0.9.4/src/scst_targ.c:54
> > > > > #6  0xf8d5af99 in scst_cmd_tasklet (p=<value optimized out>)
> > > > >     at /root/mid-level/scst-0.9.4/src/scst_targ.c:2672
> > > > > #7  0xc012d905 in tasklet_action (a=<value optimized out>)
> > > > >     at kernel/softirq.c:267
> > > > > #8  0xc012d552 in __do_softirq () at kernel/softirq.c:95
> > > > > #9  0xc010619e in do_softirq () at arch/i386/kernel/irq.c:187
> > > > > #10 0xc012d689 in irq_exit () at kernel/softirq.c:169
> > > > > #11 0xc010604e in do_IRQ (regs=0xc1cf4f48) at arch/i386/kernel/irq.c:110
> > > > > #12 0xc010499e in common_interrupt () at thread_info.h:91
> > > > > #13 0xc1cf4000 in ?? ()
> > > > > #14 0x00000000 in ?? ()
> > > > > 
> > > > > 
> > > > > I can reproduce this easily every time. Let me know if you want any
> > > > > further information about this.
> > > > > 
> > > > > ...Brad Johnson
> > > > > 
> > > > > 
> > > > > 
> > > > > 
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> > > 
> > > 
> > > 
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> > 
> 
> 
> 
> -------------------------------------------------------
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