linux/include/scsi
Boaz Harrosh 769ba8d920 ore: RAID5 Write
This is finally the RAID5 Write support.

The bigger part of this patch is not the XOR engine itself, But the
read4write logic, which is a complete mini prepare_for_striping
reading engine that can read scattered pages of a stripe into cache
so it can be used for XOR calculation. That is, if the write was not
stripe aligned.

The main algorithm behind the XOR engine is the 2 dimensional array:
	struct __stripe_pages_2d.
A drawing might save 1000 words
---

__stripe_pages_2d
       |
 n = pages_in_stripe_unit;
 w = group_width - parity;
       |                            pages array presented to the XOR lib
       |                                                |
       V                                                |
 __1_page_stripe[0].pages --> [c0][c1]..[cw][c_par] <---|
       |                                                |
 __1_page_stripe[1].pages --> [c0][c1]..[cw][c_par] <---
       |
...    |                         ...
       |
 __1_page_stripe[n].pages --> [c0][c1]..[cw][c_par]
                               ^
                               |
           data added columns first then row

---
The pages are put on this array columns first. .i.e:
	p0-of-c0, p1-of-c0, ... pn-of-c0, p0-of-c1, ...
So we are doing a corner turn of the pages.

Note that pages will zigzag down and left. but are put sequentially
in growing order. So when the time comes to XOR the stripe, only the
beginning and end of the array need be checked. We scan the array
and any NULL spot will be field by pages-to-be-read.

The FS that wants to support RAID5 needs to supply an
operations-vector that searches a given page in cache, and specifies
if the page is uptodate or need reading. All these pages to be read
are put on a slave ore_io_state and synchronously read. All the pages
of a stripe are read in one IO, using the scatter gather mechanism.

In write we constrain our IO to only be incomplete on a single
stripe. Meaning either the complete IO is within a single stripe so
we might have pages to read from both beginning  or end of the
strip. Or we have some reading to do at beginning but end at strip
boundary. The left over pages are pushed to the next IO by the API
already established by previous work, where an IO offset/length
combination presented to the ORE might get the length truncated and
the user must re-submit the leftover pages. (Both exofs and NFS
support this)

But any ORE user should make it's best effort to align it's IO
before hand and avoid complications. A cached ore_layout->stripe_size
member can be used for that calculation. (NOTE: that ORE demands
that stripe_size may not be bigger then 32bit)

What else? Well read it and tell me.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
2011-10-24 17:15:33 -07:00
..
fc Fix common misspellings 2011-03-31 11:26:23 -03:00
fc_encode.h [SCSI] libfc: introduce __fc_fill_fc_hdr that accepts fc_hdr as an argument 2011-02-28 18:32:33 -06:00
fc_frame.h [SCSI] fcoe: remove unused ptype field in fcoe_rcv_info 2011-07-28 12:08:55 +04:00
iscsi_if.h Fix common misspellings 2011-03-31 11:26:23 -03:00
iscsi_proto.h iscsi: Add Serial Number Arithmetic LT and GT into iscsi_proto.h 2011-07-25 07:48:08 +00:00
Kbuild [SCSI] Unexport scsi/scsi.h from headers_install 2010-05-02 11:45:12 -04:00
libfc.h [SCSI] libfc, tcm_fc: add ddp_targ() to libfc function template to supprot FCoE DDP in target mode 2011-06-29 16:28:39 -05:00
libfcoe.h [SCSI] libfcoe: Move FCOE_MTU definition from fcoe.h to libfcoe.h 2011-02-28 18:33:12 -06:00
libiscsi_tcp.h Fix common misspellings 2011-03-31 11:26:23 -03:00
libiscsi.h iscsi: Use struct scsi_lun in iscsi structs instead of u8[8] 2011-07-25 07:47:59 +00:00
libsas.h [SCSI] libsas: Add option for SATA soft reset 2011-05-26 22:49:33 -05:00
libsrp.h libsrp: fix compile failure 2009-12-30 12:23:27 -08:00
osd_attributes.h [SCSI] libosd: OSD2r05: Attribute definitions 2009-06-10 08:54:07 -05:00
osd_initiator.h treewide: Fix recieve/receive typos 2011-06-24 11:18:57 +02:00
osd_ore.h ore: RAID5 Write 2011-10-24 17:15:33 -07:00
osd_protocol.h [SCSI] libosd: Support for scatter gather write/read commands 2010-10-26 10:42:34 -05:00
osd_sec.h [SCSI] libosd: OSDv1 Headers 2009-03-12 12:58:06 -05:00
osd_sense.h [SCSI] libosd: osd_sense: OSD_CFO_PERMISSIONS 2009-12-04 12:01:44 -06:00
osd_types.h [SCSI] libosd: Support for scatter gather write/read commands 2010-10-26 10:42:34 -05:00
sas_ata.h libsas: convert to libata new error handler 2011-03-02 02:36:45 -05:00
sas.h [SCSI] libsas: Convert sas_proto users to sas_protocol 2008-01-11 18:22:41 -06:00
scsi_bsg_fc.h [SCSI] fc-transport: Use packed modifier for fc_bsg_request structure. 2010-01-17 12:36:33 -06:00
scsi_cmnd.h [SCSI] Deprecate SCSI_PROT_*_CONVERT operations 2009-10-02 09:46:25 -05:00
scsi_dbg.h [SCSI] Fix device not ready printk 2007-10-12 14:51:56 -04:00
scsi_device.h atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
scsi_devinfo.h Merge ../scsi-rc-fixes-2.6 2006-04-14 15:47:45 -05:00
scsi_dh.h [SCSI] scsi_dh: Change the scsidh_activate interface to be asynchronous 2009-12-04 12:00:46 -06:00
scsi_driver.h sd, sr: fix Driver 'sd' needs updating message 2009-06-21 12:01:27 -05:00
scsi_eh.h [SCSI] scsi_eh_prep_cmnd should save scmd->underflow 2008-07-26 15:14:56 -04:00
scsi_host.h Fix common misspellings 2011-03-31 11:26:23 -03:00
scsi_ioctl.h [PATCH] don't mess with file in scsi_nonblockable_ioctl() 2008-10-21 07:47:28 -04:00
scsi_netlink_fc.h [SCSI] SCSI & FC transport: extend event vendor id's to 64bits 2006-09-02 15:35:15 -05:00
scsi_netlink.h scsi: use __uX types for headers exported to user space 2010-08-11 08:59:01 -07:00
scsi_scan.h PM/Hibernate: Wait for SCSI devices scan to complete during resume 2009-04-13 11:37:07 -07:00
scsi_tcq.h [SCSI] target: Convert TASK_ATTR to scsi_tcq.h definitions 2011-05-24 13:03:56 -04:00
scsi_tgt_if.h [SCSI] tgt: add I_T nexus support 2007-10-12 14:37:50 -04:00
scsi_tgt.h [SCSI] tgt: add I_T nexus support 2007-10-12 14:37:50 -04:00
scsi_transport_fc.h Fix common misspellings 2011-03-31 11:26:23 -03:00
scsi_transport_iscsi.h [SCSI] iscsi class: add callout to get iscsi_endpoint values 2011-02-24 12:41:12 -05:00
scsi_transport_sas.h [SCSI] scsi_transport_sas: add support for transport layer retries (TLR) 2010-02-08 17:15:19 -06:00
scsi_transport_spi.h [SCSI] aic79xx: make driver respect nvram for IU and QAS settings 2009-06-15 10:09:35 -05:00
scsi_transport_srp.h [SCSI] tgt: move tsk_mgmt_response callback to transport class 2007-10-12 14:38:01 -04:00
scsi_transport.h block: unify request timeout handling 2008-10-09 08:56:13 +02:00
scsi.h treewide: fix potentially dangerous trailing ';' in #defined values/expressions 2011-07-21 14:10:00 +02:00
scsicam.h
sg.h sysctl extern cleanup: sg 2010-03-12 15:53:10 -08:00
srp.h IB/srp: Implement SRP_CRED_REQ and SRP_AER_REQ 2010-10-22 22:19:10 -07:00