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  1. 25 Oct, 2011 1 commit
    • Boaz Harrosh's avatar
      ore: RAID5 Write · 769ba8d9
      Boaz Harrosh authored 
      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: default avatarBoaz Harrosh <bharrosh@panasas.com>
      769ba8d9
  3. 24 Oct, 2011 3 commits
    • Boaz Harrosh's avatar
      ore: RAID5 read · a1fec1db
      Boaz Harrosh authored 
      This patch introduces the first stage of RAID5 support
mainly the skip-over-raid-units when reading. For
writes it inserts BLANK units, into where XOR blocks
should be calculated and written to.

It introduces the new "general raid maths", and the main
additional parameters and components needed for raid5.

Since at this stage it could corrupt future version that
actually do support raid5. The enablement of raid5
mounting and setting of parity-count > 0 is disabled. So
the raid5 code will never be used. Mounting of raid5 is
only enabled later once the basic XOR write is also in.
But if the patch "enable RAID5" is applied this code has
been tested to be able to properly read raid5 volumes
and is according to standard.

Also it has been tested that the new maths still properly
supports RAID0 and grouping code just as before.
(BTW: I have found more bugs in the pnfs-obj RAID math
 fixed here)

The ore.c file is getting too big, so new ore_raid.[hc]
files are added that will include the special raid stuff
that are not used in striping and mirrors. In future write
support these will get bigger.
When adding the ore_raid.c to Kbuild file I was forced to
rename ore.ko to libore.ko. Is it possible to keep source
file, say ore.c and module file ore.ko the same even if there
are multiple files inside ore.ko?
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      a1fec1db
    • Boaz Harrosh's avatar
      fs/Makefile: Always inspect exofs/ · 3e335672
      Boaz Harrosh authored 
      fs/exofs directory has multiple targets now, of which the
ore.ko will be needed by the pnfs-objects-layout-driver
(fs/nfs/objlayout).

As suggested by: Michal Marek <mmarek@suse.cz>  convert
inclusion of exofs/ from obj-$(CONFIG_EXOFS_FS) => obj-$(y).
So ORE can be selected also from fs/nfs/Kconfig

CC: Michal Marek <mmarek@suse.cz>
CC: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      3e335672
    • Boaz Harrosh's avatar
      ore: Make ore_calc_stripe_info EXPORT_SYMBOL · 611d7a5d
      Boaz Harrosh authored 
      ore_calc_stripe_info is needed by exofs::export.c
for the layout calculations. Make it exportable
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      611d7a5d
  5. 14 Oct, 2011 8 commits
    • Boaz Harrosh's avatar
      ore/exofs: Change ore_check_io API · 4b46c9f5
      Boaz Harrosh authored 
      Current ore_check_io API receives a residual
pointer, to report partial IO. But it is actually
not used, because in a multiple devices IO there
is never a linearity in the IO failure.

On the other hand if every failing device is reported
through a received callback measures can be taken to
handle only failed devices. One at a time.

This will also be needed by the objects-layout-driver
for it's error reporting facility.

Exofs is not currently using the new information and
keeps the old behaviour of failing the complete IO in
case of an error. (No partial completion)

TODO: Use an ore_check_io callback to set_page_error only
the failing pages. And re-dirty write pages.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      4b46c9f5
    • Boaz Harrosh's avatar
      ore/exofs: Define new ore_verify_layout · 5a51c0c7
      Boaz Harrosh authored 
      All users of the ore will need to check if current code
supports the given layout. For example RAID5/6 is not
currently supported.

So move all the checks from exofs/super.c to a new
ore_verify_layout() to be used by ore users.

Note that any new layout should be passed through the
ore_verify_layout() because the ore engine will prepare
and verify some internal members of ore_layout, and
assumes it's called.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      5a51c0c7
    • Boaz Harrosh's avatar
      ore: Support for partial component table · 3bd98568
      Boaz Harrosh authored 
      Users like the objlayout-driver would like to only pass
a partial device table that covers the IO in question.
For example exofs divides the file into raid-group-sized
chunks and only serves group_width number of devices at
a time.

The partiality is communicated by setting
ore_componets->first_dev and the array covers all logical
devices from oc->first_dev upto (oc->first_dev + oc->numdevs)

The ore_comp_dev() API receives a logical device index
and returns the actual present device in the table.
An out-of-range dev_index will BUG.

Logical device index is the theoretical device index as if
all the devices of a file are present. .i.e:
	total_devs = group_width * mirror_p1 * group_count
	0 <= dev_index < total_devs
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      3bd98568
    • Boaz Harrosh's avatar
      ore: Support for short read/writes · bbf9a31b
      Boaz Harrosh authored 
      Memory conditions and max_bio constraints might cause us to
not comply to the full length of the requested IO. Instead of
failing the complete IO we can issue a shorter read/write and
report how much was actually executed in the ios->length
member.

All users must check ios->length at IO_done or upon return of
ore_read/write and re-issue the reminder of the bytes. Because
other wise there is no error returned like before.

This is part of the effort to support the pnfs-obj layout driver.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      bbf9a31b
    • Boaz Harrosh's avatar
      exofs: Support for short read/writes · 154a9300
      Boaz Harrosh authored 
      If at read/write_done the actual IO was shorter then requested,
reported in returned ios->length. It is not an error. The reminder
of the pages should just be unlocked but not marked uptodate or
end_page_writeback. They will be re issued later by the VFS.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      154a9300
    • Boaz Harrosh's avatar
      ore: Remove check for ios->kern_buff in _prepare_for_striping to later · 6851a5e5
      Boaz Harrosh authored 
      Move the check and preparation of the ios->kern_buff case to
later inside _write_mirror().

Since read was never used with ios->kern_buff its support is removed
instead of fixed.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      6851a5e5
    • Boaz Harrosh's avatar
      ore: cleanup: Embed an ore_striping_info inside ore_io_state · 98260754
      Boaz Harrosh authored 
      Now that each ore_io_state covers only a single raid group.
A single striping_info math is needed. Embed one inside
ore_io_state to cache the calculation results and eliminate
an extra call.

Also the outer _prepare_for_striping is removed since it does nothing.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      98260754
    • Boaz Harrosh's avatar
      ore: Only IO one group at a time (API change) · b916c5cd
      Boaz Harrosh authored 
      Usually a single IO is confined to one group of devices
(group_width) and at the boundary of a raid group it can
spill into a second group. Current code would allocate a
full device_table size array at each io_state so it can
comply to requests that span two groups. Needless to say
that is very wasteful, specially when device_table count
can get very large (hundreds even thousands), while a
group_width is usually 8 or 10.

* Change ore API to trim on IO that spans two raid groups.
  The user passes offset+length to ore_get_rw_state, the
  ore might trim on that length if spanning a group boundary.
  The user must check ios->length or ios->nrpages to see
  how much IO will be preformed. It is the responsibility
  of the user to re-issue the reminder of the IO.

* Modify exofs To copy spilled pages on to the next IO.
  This means one last kick is needed after all coalescing
  of pages is done.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      b916c5cd
  7. 04 Oct, 2011 1 commit
    • Boaz Harrosh's avatar
      ore/exofs: Change the type of the devices array (API change) · d866d875
      Boaz Harrosh authored 
      In the pNFS obj-LD the device table at the layout level needs
to point to a device_cache node, where it is possible and likely
that many layouts will point to the same device-nodes.

In Exofs we have a more orderly structure where we have a single
array of devices that repeats twice for a round-robin view of the
device table

This patch moves to a model that can be used by the pNFS obj-LD
where struct ore_components holds an array of ore_dev-pointers.
(ore_dev is newly defined and contains a struct osd_dev *od
 member)

Each pointer in the array of pointers will point to a bigger
user-defined dev_struct. That can be accessed by use of the
container_of macro.

In Exofs an __alloc_dev_table() function allocates the
ore_dev-pointers array as well as an exofs_dev array, in one
allocation and does the addresses dance to set everything pointing
correctly. It still keeps the double allocation trick for the
inodes round-robin view of the table.

The device table is always allocated dynamically, also for the
single device case. So it is unconditionally freed at umount.
Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
      d866d875
  9. 03 Oct, 2011 5 commits
  11. 22 Sep, 2011 1 commit
  13. 12 Sep, 2011 9 commits
  15. 11 Sep, 2011 12 commits
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