Commit Graph

13 Commits

Author SHA1 Message Date
Kiyoshi Ueda
2e93ccc193 [PATCH] dm: suspend: add noflush pushback
In device-mapper I/O is sometimes queued within targets for later processing.
For example the multipath target can be configured to store I/O when no paths
are available instead of returning it -EIO.

This patch allows the device-mapper core to instruct a target to transfer the
contents of any such in-target queue back into the core.  This frees up the
resources used by the target so the core can replace that target with an
alternative one and then resend the I/O to it.  Without this patch the only
way to change the target in such circumstances involves returning the I/O with
an error back to the filesystem/application.  In the multipath case, this
patch will let us add new paths for existing I/O to try after all the existing
paths have failed.

    DMF_NOFLUSH_SUSPENDING
    ----------------------

If the DM_NOFLUSH_FLAG ioctl option is specified at suspend time, the
DMF_NOFLUSH_SUSPENDING flag is set in md->flags during dm_suspend().  It
is always cleared before dm_suspend() returns.

The flag must be visible while the target is flushing pending I/Os so it
is set before presuspend where the flush starts and unset after the wait
for md->pending where the flush ends.

Target drivers can check this flag by calling dm_noflush_suspending().

    DM_MAPIO_REQUEUE / DM_ENDIO_REQUEUE
    -----------------------------------

A target's map() function can now return DM_MAPIO_REQUEUE to request the
device mapper core queue the bio.

Similarly, a target's end_io() function can return DM_ENDIO_REQUEUE to request
the same.  This has been labelled 'pushback'.

The __map_bio() and clone_endio() functions in the core treat these return
values as errors and call dec_pending() to end the I/O.

    dec_pending
    -----------

dec_pending() saves the pushback request in struct dm_io->error.  Once all
the split clones have ended, dec_pending() will put the original bio on
the md->pushback list.  Note that this supercedes any I/O errors.

It is possible for the suspend with DM_NOFLUSH_FLAG to be aborted while
in progress (e.g. by user interrupt).  dec_pending() checks for this and
returns -EIO if it happened.

    pushdback list and pushback_lock
    --------------------------------

The bio is queued on md->pushback temporarily in dec_pending(), and after
all pending I/Os return, md->pushback is merged into md->deferred in
dm_suspend() for re-issuing at resume time.

md->pushback_lock protects md->pushback.
The lock should be held with irq disabled because dec_pending() can be
called from interrupt context.

Queueing bios to md->pushback in dec_pending() must be done atomically
with the check for DMF_NOFLUSH_SUSPENDING flag.  So md->pushback_lock is
held when checking the flag.  Otherwise dec_pending() may queue a bio to
md->pushback after the interrupted dm_suspend() flushes md->pushback.
Then the bio would be left in md->pushback.

Flag setting in dm_suspend() can be done without md->pushback_lock because
the flag is checked only after presuspend and the set value is already
made visible via the target's presuspend function.

The flag can be checked without md->pushback_lock (e.g. the first part of
the dec_pending() or target drivers), because the flag is checked again
with md->pushback_lock held when the bio is really queued to md->pushback
as described above.  So even if the flag is cleared after the lockless
checkings, the bio isn't left in md->pushback but returned to applications
with -EIO.

    Other notes on the current patch
    --------------------------------

- md->pushback is added to the struct mapped_device instead of using
  md->deferred directly because md->io_lock which protects md->deferred is
  rw_semaphore and can't be used in interrupt context like dec_pending(),
  and md->io_lock protects the DMF_BLOCK_IO flag of md->flags too.

- Don't issue lock_fs() in dm_suspend() if the DM_NOFLUSH_FLAG
  ioctl option is specified, because I/Os generated by lock_fs() would be
  pushed back and never return if there were no valid devices.

- If an error occurs in dm_suspend() after the DMF_NOFLUSH_SUSPENDING
  flag is set, md->pushback must be flushed because I/Os may be queued to
  the list already.  (flush_and_out label in dm_suspend())

    Test results
    ------------

I have tested using multipath target with the next patch.

The following tests are for regression/compatibility:
  - I/Os succeed when valid paths exist;
  - I/Os fail when there are no valid paths and queue_if_no_path is not
    set;
  - I/Os are queued in the multipath target when there are no valid paths and
    queue_if_no_path is set;
  - The queued I/Os above fail when suspend is issued without the
    DM_NOFLUSH_FLAG ioctl option.  I/Os spanning 2 multipath targets also
    fail.

The following tests are for the normal code path of new pushback feature:
  - Queued I/Os in the multipath target are flushed from the target
    but don't return when suspend is issued with the DM_NOFLUSH_FLAG
    ioctl option;
  - The I/Os above are queued in the multipath target again when
    resume is issued without path recovery;
  - The I/Os above succeed when resume is issued after path recovery
    or table load;
  - Queued I/Os in the multipath target succeed when resume is issued
    with the DM_NOFLUSH_FLAG ioctl option after table load. I/Os
    spanning 2 multipath targets also succeed.

The following tests are for the error paths of the new pushback feature:
  - When the bdget_disk() fails in dm_suspend(), the
    DMF_NOFLUSH_SUSPENDING flag is cleared and I/Os already queued to the
    pushback list are flushed properly.
  - When suspend with the DM_NOFLUSH_FLAG ioctl option is interrupted,
      o I/Os which had already been queued to the pushback list
        at the time don't return, and are re-issued at resume time;
      o I/Os which hadn't been returned at the time return with EIO.

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:29:09 -08:00
Kiyoshi Ueda
45cbcd7983 [PATCH] dm: map and endio return code clarification
Tighten the use of return values from the target map and end_io functions.
Values of 2 and above are now explictly reserved for future use.  There are no
existing targets using such values.

The patch has no effect on existing behaviour.

o Reserve return values of 2 and above from target map functions.
  Any positive value currently indicates "mapping complete", but all
  existing drivers use the value 1.  We now make that a requirement
  so we can assign new meaning to higher values in future.

  The new definition of return values from target map functions is:
      < 0 : error
      = 0 : The target will handle the io (DM_MAPIO_SUBMITTED).
      = 1 : Mapping completed (DM_MAPIO_REMAPPED).
      > 1 : Reserved (undefined).  Previously this was the same as '= 1'.

o Reserve return values of 2 and above from target end_io functions
  for similar reasons.
  DM_ENDIO_INCOMPLETE is introduced for a return value of 1.

Test results:

  I have tested by using the multipath target.

  I/Os succeed when valid paths exist.

  I/Os are queued in the multipath target when there are no valid paths and
queue_if_no_path is set.

  I/Os fail when there are no valid paths and queue_if_no_path is not set.

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:29:09 -08:00
Kiyoshi Ueda
a3d77d35be [PATCH] dm: suspend: parameter change
Change the interface of dm_suspend() so that we can pass several options
without increasing the number of parameters.  The existing 'do_lockfs' integer
parameter is replaced by a flag DM_SUSPEND_LOCKFS_FLAG.

There is no functional change to the code.

Test results:
I have tested 'dmsetup suspend' command with/without the '--nolockfs'
option and confirmed the do_lockfs value is correctly set.

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:29:09 -08:00
Bryn Reeves
999d816851 [PATCH] dm table: add target flush
This patch adds support for a per-target dm_flush_fn method.  This is needed
to allow dm-loop to invalidate page cache mappings in response to BLKFLSBUF
ioctl commands.

Signed-off-by: Bryn Reeves <breeves@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:16 -07:00
Bryn Reeves
3cb4021453 [PATCH] dm: extract device limit setting
Separate the setting of device I/O limits from dm_get_device().  dm-loop will
use this.

Signed-off-by: Bryn Reeves <breeves@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:16 -07:00
Milan Broz
8757b7764f [PATCH] dm table: add target preresume
This patch adds a target preresume hook.

It is called before the targets are resumed and if it returns an error the
resume gets cancelled.

The crypt target will use this to indicate that it is unable to process I/O
because no encryption key has been supplied.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:15 -07:00
Milan Broz
aa129a2247 [PATCH] dm: support ioctls on mapped devices
Extend the core device-mapper infrastructure to accept arbitrary ioctls on a
mapped device provided that it has exactly one target and it is capable of
supporting ioctls.

[We can't use unlocked_ioctl because we need 'inode': 'file' might be NULL.
Is it worth changing this?]

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

Arnd Bergmann <arnd@arndb.de> wrote:

> Am Wednesday 21 June 2006 21:31 schrieb Alasdair G Kergon:
> > static struct block_device_operations dm_blk_dops = {
> > .open = dm_blk_open,
> > .release = dm_blk_close,
> > +.ioctl = dm_blk_ioctl,
> > .getgeo = dm_blk_getgeo,
> > .owner = THIS_MODULE
>
> I guess this also needs a ->compat_ioctl method, otherwise it won't
> work for ioctl numbers that have a compat_ioctl implementation in the
> low-level device driver.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:13 -07:00
Alasdair G Kergon
72d9486169 [PATCH] dm: improve error message consistency
Tidy device-mapper error messages to include context information
automatically.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 09:58:36 -07:00
David Teigland
c2ade42dd3 [PATCH] dm: create error table
Add a library function dm_create_error_table() to create a table that rejects
any I/O sent to a device with EIO.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 09:58:36 -07:00
Alasdair G Kergon
17b2f66f2a [PATCH] dm: add exports
Move definitions of core device-mapper functions for manipulating mapped
devices and their tables to <linux/device-mapper.h> advertising their
availability for use elsewhere in the kernel.

Protect the contents of device-mapper.h with ifdef __KERNEL__.  And throw
in a few formatting clean-ups and extra comments.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 09:58:36 -07:00
NeilBrown
969429b504 [PATCH] dm: make sure QUEUE_FLAG_CLUSTER is set properly
This flag should be set for a virtual device iff it is set for all
underlying devices.

Signed-off-by: Neil Brown <neilb@suse.de>
Acked-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:59 -08:00
Alasdair G Kergon
3ee247ebce [PATCH] dm: dm-table warning fix
drivers/md/dm-table.c:500: warning: comparison of distinct pointer types lacks a cast

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-01 08:53:11 -08:00
Linus Torvalds
1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00