linux-toradex.git/drivers/md/dm-mpath.c, branch v4.4.91

dm mpath: check if path's request_queue is dying in activate_path()

2016-10-28T07:01:28+00:00

commit f10e06b744074824fb8ec7066bc03ecc90918f5b upstream.

If pg_init_retries is set and a request is queued against a multipath
device with all underlying block device request_queues in the "dying"
state then an infinite loop is triggered because activate_path() never
succeeds and hence never calls pg_init_done().

This change avoids that device removal triggers an infinite loop by
failing the activate_path() which causes the "dying" path to be failed.

Reported-by: Bart Van Assche 
Signed-off-by: Mike Snitzer 
Signed-off-by: Greg Kroah-Hartman

dm mpath: fix infinite recursion in ioctl when no paths and !queue_if_no_path

2015-11-17T19:19:00+00:00

In multipath_prepare_ioctl(),
  - pgpath is a path selected from available paths
  - m->queue_io is true if we cannot send a request immediately to
    paths, either because:
      * there is no available path
      * the path group needs activation (pg_init)
          - pg_init is not started
          - pg_init is still running
  - m->queue_if_no_path is true if the device is configured to queue
    I/O if there are no available paths

If !pgpath && !m->queue_if_no_path, the handler should return -EIO.
However in the course of refactoring the condition check has broken
and returns success in that case.  Since bdev points to the dm device
itself, dm_blk_ioctl() calls __blk_dev_driver_ioctl() for itself and
recurses until crash.

You could reproduce the problem like this:

  # dmsetup create mp --table '0 1024 multipath 0 0 0 0'
  # sg_inq /dev/mapper/mp
  
  [  172.648615] BUG: unable to handle kernel paging request at fffffffc81b10268
  [  172.662843] PGD 19dd067 PUD 0
  [  172.666269] Thread overran stack, or stack corrupted
  [  172.671808] Oops: 0000 [#1] SMP
  ...

Fix the condition check with some clarifications.

Fixes: e56f81e0b01e ("dm: refactor ioctl handling")
Signed-off-by: Jun'ichi Nomura 
Cc: Christoph Hellwig 
Cc: Mike Snitzer 
Signed-off-by: Mike Snitzer

dm: fix ioctl retry termination with signal

2015-11-17T19:04:32+00:00

dm-mpath retries ioctl, when no path is readily available and the device
is configured to queue I/O in such a case. If you want to stop the retry
before multipathd decides to turn off queueing mode, you could send
signal for the process to exit from the loop.

However the check of fatal signal has not carried along when commit
6c182cd88d17 ("dm mpath: fix ioctl deadlock when no paths") moved the
loop from dm-mpath to dm core. As a result, we can't terminate such
a process in the retry loop.

Easy reproducer of the situation is:

  # dmsetup create mp --table '0 1024 multipath 0 0 0 0'
  # dmsetup message mp 0 'queue_if_no_path'
  # sg_inq /dev/mapper/mp

then you should be able to terminate sg_inq by pressing Ctrl+C.

Fixes: 6c182cd88d17 ("dm mpath: fix ioctl deadlock when no paths")
Signed-off-by: Jun'ichi Nomura 
Cc: Hannes Reinecke 
Cc: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Cc: stable@vger.kernel.org

dm: add support for passing through persistent reservations

2015-10-31T23:05:59+00:00

This adds support to pass through persistent reservation requests
similar to the existing ioctl handling, and with the same limitations,
e.g. devices may only have a single target attached.

This is mostly intended for multipathing.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Mike Snitzer

dm: refactor ioctl handling

2015-10-31T23:05:59+00:00

This moves the call to blkdev_ioctl and the argument checking to DM core
code, and only leaves a callout to find the block device to operate on
in the targets.  This simplifies the code and allows us to pass through
ioctl-like command using other methods in the next patch.

Also split out a helper around calling the prepare_ioctl method that
will be reused for persistent reservation handling.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Mike Snitzer

Revert "dm mpath: fix stalls when handling invalid ioctls"

2015-10-31T22:53:51+00:00

This reverts commit a1989b330093578ea5470bea0a00f940c444c466.

That commit introduced a regression at least for the case of the SG_IO ioctl()
running without CAP_SYS_RAWIO capability (e.g., unprivileged users) when there
are no active paths: the ioctl() fails with the ENOTTY errno immediately rather
than blocking due to queue_if_no_path until a path becomes active, for example.

That case happens to be exercised by QEMU KVM guests with 'scsi-block' devices
(qemu "-device scsi-block" [1], libvirt "" [2])
from multipath devices; which leads to SCSI/filesystem errors in such a guest.

More general scenarios can hit that regression too. The following demonstration
employs a SG_IO ioctl() with a standard SCSI INQUIRY command for this objective
(some output & user changes omitted for brevity and comments added for clarity).

Reverting that commit restores normal operation (queueing) in failing scenarios;
tested on linux-next (next-20151022).

1) Test-case is based on sg_simple0 [3] (just SG_IO; remove SG_GET_VERSION_NUM)

    $ cat sg_simple0.c
    ... see [3] ...
    $ sed '/SG_GET_VERSION_NUM/,/}/d' sg_simple0.c > sgio_inquiry.c
    $ gcc sgio_inquiry.c -o sgio_inquiry

2) The ioctl() works fine with active paths present.

    # multipath -l 85ag56
    85ag56 (...) dm-19 IBM     ,2145
    size=60G features='1 queue_if_no_path' hwhandler='0' wp=rw
    |-+- policy='service-time 0' prio=0 status=active
    | |- 8:0:11:0  sdz  65:144  active undef running
    | `- 9:0:9:0   sdbf 67:144  active undef running
    `-+- policy='service-time 0' prio=0 status=enabled
      |- 8:0:12:0  sdae 65:224  active undef running
      `- 9:0:12:0  sdbo 68:32   active undef running

    $ ./sgio_inquiry /dev/mapper/85ag56
    Some of the INQUIRY command's response:
        IBM       2145              0000
    INQUIRY duration=0 millisecs, resid=0

3) The ioctl() fails with ENOTTY errno with _no_ active paths present,
   for unprivileged users (rather than blocking due to queue_if_no_path).

    # for path in $(multipath -l 85ag56 | grep -o 'sd[a-z]\+'); \
          do multipathd -k"fail path $path"; done

    # multipath -l 85ag56
    85ag56 (...) dm-19 IBM     ,2145
    size=60G features='1 queue_if_no_path' hwhandler='0' wp=rw
    |-+- policy='service-time 0' prio=0 status=enabled
    | |- 8:0:11:0  sdz  65:144  failed undef running
    | `- 9:0:9:0   sdbf 67:144  failed undef running
    `-+- policy='service-time 0' prio=0 status=enabled
      |- 8:0:12:0  sdae 65:224  failed undef running
      `- 9:0:12:0  sdbo 68:32   failed undef running

    $ ./sgio_inquiry /dev/mapper/85ag56
    sg_simple0: Inquiry SG_IO ioctl error: Inappropriate ioctl for device

4) dmesg shows that scsi_verify_blk_ioctl() failed for SG_IO (0x2285);
   it returns -ENOIOCTLCMD, later replaced with -ENOTTY in vfs_ioctl().

    $ dmesg
    <...>
    [] device-mapper: multipath: Failing path 65:144.
    [] device-mapper: multipath: Failing path 67:144.
    [] device-mapper: multipath: Failing path 65:224.
    [] device-mapper: multipath: Failing path 68:32.
    [] sgio_inquiry: sending ioctl 2285 to a partition!

5) The ioctl() only works if the SYS_CAP_RAWIO capability is present
   (then queueing happens -- in this example, queue_if_no_path is set);
   this is due to a conditional check in scsi_verify_blk_ioctl().

    # capsh --drop=cap_sys_rawio -- -c './sgio_inquiry /dev/mapper/85ag56'
    sg_simple0: Inquiry SG_IO ioctl error: Inappropriate ioctl for device

    # ./sgio_inquiry /dev/mapper/85ag56 &
    [1] 72830

    # cat /proc/72830/stack
    [] 0xc00000171c0df700
    [] __switch_to+0x204/0x350
    [] msleep+0x5c/0x80
    [] dm_blk_ioctl+0x70/0x170
    [] blkdev_ioctl+0x2b0/0x9b0
    [] block_ioctl+0x64/0xd0
    [] do_vfs_ioctl+0x490/0x780
    [] SyS_ioctl+0xd4/0xf0
    [] system_call+0x38/0xd0

6) This is the function call chain exercised in this analysis:

SYSCALL_DEFINE3(ioctl, <...>) @ fs/ioctl.c
    -> do_vfs_ioctl()
        -> vfs_ioctl()
            ...
            error = filp->f_op->unlocked_ioctl(filp, cmd, arg);
            ...
                -> dm_blk_ioctl() @ drivers/md/dm.c
                    -> multipath_ioctl() @ drivers/md/dm-mpath.c
                        ...
                        (bdev = NULL, due to no active paths)
                        ...
                        if (!bdev || <...>) {
                            int err = scsi_verify_blk_ioctl(NULL, cmd);
                            if (err)
                                r = err;
                        }
                        ...
                            -> scsi_verify_blk_ioctl() @ block/scsi_ioctl.c
                                ...
                                if (bd && bd == bd->bd_contains) // not taken (bd = NULL)
                                    return 0;
                                ...
                                if (capable(CAP_SYS_RAWIO)) // not taken (unprivileged user)
                                    return 0;
                                ...
                                printk_ratelimited(KERN_WARNING
                                           "%s: sending ioctl %x to a partition!\n" <...>);

                                return -ENOIOCTLCMD;
                            <-
                        ...
                        return r ? : <...>
                    <-
            ...
            if (error == -ENOIOCTLCMD)
                error = -ENOTTY;
             out:
                return error;
            ...

Links:
[1] http://git.qemu.org/?p=qemu.git;a=commit;h=336a6915bc7089fb20fea4ba99972ad9a97c5f52
[2] https://libvirt.org/formatdomain.html#elementsDisks (see 'disk' -> 'device')
[3] http://tldp.org/HOWTO/SCSI-Generic-HOWTO/pexample.html (Revision 1.2, 2002-05-03)

Signed-off-by: Mauricio Faria de Oliveira 
Signed-off-by: Mike Snitzer 
Cc: stable@vger.kernel.org

dm-mpath, scsi_dh: request scsi_dh modules in scsi_dh, not dm-mpath

2015-08-28T20:14:55+00:00

This way we can reused the same code any attachment method, not just those
requested from dm-mpath.

[jejb: fixup checkpatch error]
Signed-off-by: Christoph Hellwig 
Reviewed-by: Martin K. Petersen 
Reviewed-by: Hannes Reinecke 
Acked-by: Mike Snitzer 
Signed-off-by: James Bottomley

dm-mpath, scsi_dh: don't let dm detach device handlers

2015-08-28T20:14:54+00:00

While allowing dm-mpath to attach device handlers is a functionality we need
for backwards compatibility reason there is no reason to reference count
them and detach them if dm-mpath stops using the device for some reason.

If the device handler works for the given device it can just stay attached,
and we can take the retain_hw_handler codepath.

Signed-off-by: Christoph Hellwig 
Acked-by: Mike Snitzer 
Acked-by: Hannes Reinecke 
Signed-off-by: James Bottomley

dm mpath: fix leak of dm_mpath_io structure in blk-mq .queue_rq error path

2015-05-27T21:37:22+00:00

Otherwise kmemleak reported:

unreferenced object 0xffff88009b14e2b0 (size 16):
  comm "fio", pid 4274, jiffies 4294978034 (age 1253.210s)
  hex dump (first 16 bytes):
    40 12 f3 99 01 88 ff ff 00 10 00 00 00 00 00 00  @...............
  backtrace:
    [] kmemleak_alloc+0x49/0xb0
    [] kmem_cache_alloc+0xf8/0x160
    [] mempool_alloc_slab+0x10/0x20
    [] mempool_alloc+0x57/0x150
    [] __multipath_map.isra.17+0xe1/0x220 [dm_multipath]
    [] multipath_clone_and_map+0x15/0x20 [dm_multipath]
    [] map_request.isra.39+0xd5/0x220 [dm_mod]
    [] dm_mq_queue_rq+0x134/0x240 [dm_mod]
    [] __blk_mq_run_hw_queue+0x1d5/0x380
    [] blk_mq_run_hw_queue+0xc5/0x100
    [] blk_sq_make_request+0x240/0x300
    [] generic_make_request+0xc0/0x110
    [] submit_bio+0x72/0x150
    [] do_blockdev_direct_IO+0x1f3b/0x2da0
    [] __blockdev_direct_IO+0x3e/0x40
    [] ext4_direct_IO+0x1aa/0x390

Fixes: e5863d9ad ("dm: allocate requests in target when stacking on blk-mq devices")
Reported-by: Bart Van Assche 
Signed-off-by: Mike Snitzer 
Cc: stable@vger.kernel.org # 4.0+

dm: optimize dm_mq_queue_rq to _not_ use kthread if using pure blk-mq

2015-04-15T16:10:17+00:00

dm_mq_queue_rq() is in atomic context so care must be taken to not
sleep -- as such GFP_ATOMIC is used for the md->bs bioset allocations
and dm-mpath's call to blk_get_request().  In the future the bioset
allocations will hopefully go away (by removing support for partial
completions of bios in a cloned request).

Also prepare for supporting DM blk-mq ontop of old-style request_fn
device(s) if a new dm-mod 'use_blk_mq' parameter is set.  The kthread
will still be used to queue work if blk-mq is used ontop of old-style
request_fn device(s).

Signed-off-by: Mike Snitzer