In the recent x2apic cleanup I got two things really wrong:
1) The safety check in __disable_x2apic which allows the function to
   be called unconditionally is backwards. The check is there to
   prevent access to the apic MSR in case that the machine has no
   apic. Though right now it returns if the machine has an apic and
   therefor the disabling of x2apic is never invoked.

2) x2apic_disable() sets x2apic_mode to 0 after registering the local
   apic. That's wrong, because register_lapic_address() checks x2apic
   mode and therefor takes the wrong code path.

This results in boot failures on machines with x2apic preenabled by
BIOS and can also lead to an fatal MSR access on machines without
apic.

The solutions are simple:
1) Correct the sanity check for apic availability
2) Clear x2apic_mode _before_ calling register_lapic_address()

Fixes: 659006b 'x86/x2apic: Split enable and setup function'
Reported-and-tested-by: Javier Monteagudo <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1224764
Cc: [email protected] # 4.0+
Cc: Laura Abbott <[email protected]>
Cc: Jiang Liu <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Borislav Petkov <[email protected]>

Jeff has been doing a lot of development (including much of the
state-locking rewrite just as one example) plus lots of review and other
miscellaneous nfsd work, so let's acknowledge the status quo.

I'll continue to be the one to send regular pull requests but Jeff will
should be available to cover there occasionally too.

Signed-off-by: J. Bruce Fields <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

…inux/kernel/git/tip/tip

Pull x86 fix from Thomas Gleixner:
 "A single fix for a APIC regression introduced in 4.0 which went
  undetected until now.

  I screwed up the x2apic cleanup in a subtle way.  The screwup is only
  visible on systems which have x2apic preenabled in the BIOS and need
  to disable it during boot"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/apic: Fix fallout from x2apic cleanup

…ways call wait_sb_inodes()

e797291 ("writeback: don't issue wb_writeback_work if clean")
updated writeback path to avoid kicking writeback work items if there
are no inodes to be written out; unfortunately, the avoidance logic
was too aggressive and broke sync_inodes_sb().

* sync_inodes_sb() must write out I_DIRTY_TIME inodes but I_DIRTY_TIME
  inodes dont't contribute to bdi/wb_has_dirty_io() tests and were
  being skipped over.

* inodes are taken off wb->b_dirty/io/more_io lists after writeback
  starts on them.  sync_inodes_sb() skipping wait_sb_inodes() when
  bdi_has_dirty_io() breaks it by making it return while writebacks
  are in-flight.

This patch fixes the breakages by

* Removing bdi_has_dirty_io() shortcut from bdi_split_work_to_wbs().
  The callers are already testing the condition.

* Removing bdi_has_dirty_io() shortcut from sync_inodes_sb() so that
  it always calls into bdi_split_work_to_wbs() and wait_sb_inodes().

* Making bdi_split_work_to_wbs() consider the b_dirty_time list for
  WB_SYNC_ALL writebacks.

Kudos to Eryu, Dave and Jan for tracking down the issue.

Signed-off-by: Tejun Heo <[email protected]>
Fixes: e797291 ("writeback: don't issue wb_writeback_work if clean")
Link: http://lkml.kernel.org/g/[email protected]
Reported-and-bisected-by: Eryu Guan <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Ted Ts'o <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Hi,

After commit f70ced0 (blk-mq: support per-distpatch_queue flush
machinery), the mtip32xx driver may oops upon module load due to walking
off the end of an array in mtip_init_cmd.  On initialization of the
flush_rq, init_request is called with request_index >= the maximum queue
depth the driver supports.  For mtip32xx, this value is used to index
into an array.  What this means is that the driver will walk off the end
of the array, and either oops or cause random memory corruption.

The problem is easily reproduced by doing modprobe/rmmod of the mtip32xx
driver in a loop.  I can typically reproduce the problem in about 30
seconds.

Now, in the case of mtip32xx, it actually doesn't support flush/fua, so
I think we can simply return without doing anything.  In addition, no
other mq-enabled driver does anything with the request_index passed into
init_request(), so no other driver is affected.  However, I'm not really
sure what is expected of drivers.  Ming, what did you envision drivers
would do when initializing the flush requests?

Signed-off-by: Jeff Moyer <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Only read 32 bits for the BLK status register in read_blk_stat().

The format and size of this register is defined in the
"NVDIMM Driver Writer's guide":

http://pmem.io/documents/NVDIMM_Driver_Writers_Guide.pdf

Signed-off-by: Ross Zwisler <[email protected]>
Reported-by: Nicholas Moulin <[email protected]>
Tested-by: Nicholas Moulin <[email protected]>
Reviewed-by: Jeff Moyer <[email protected]>
Signed-off-by: Dan Williams <[email protected]>

While in most cases commit b1d9e6b ("LSM: Switch to lists of hooks")
retained previous error returns, in three cases it altered them without
any explanation in the commit message. Restore all of them - in the
security_old_inode_init_security() case this led to reiserfs using
uninitialized data, sooner or later crashing the system (the only other
user of this function - ocfs2 - was unaffected afaict, since it passes
pre-initialized structures).

Signed-off-by: Jan Beulich <[email protected]>
Signed-off-by: Casey Schaufler <[email protected]>
Signed-off-by: James Morris <[email protected]>

…kernel/git/nvdimm/nvdimm

Pull nvdimm fix from Dan Williams:
 "A single fix for status register read size in the nd_blk driver.

  The effect of getting the width of this register read wrong is that
  all I/O fails when the read returns non-zero.  Given the availability
  of ACPI 6 NFIT enabled platforms, this could reasonably wait to come
  in during the 4.3 merge window with a tag for 4.2-stable.  Otherwise,
  this makes the 4.2 kernel fully functional with devices that conform
  to the mmio-block-apertures defined in the ACPI 6 NFIT (NVDIMM
  Firmware Interface Table)"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  nfit, nd_blk: BLK status register is only 32 bits

…/git/jmorris/linux-security

Pull LSM regression fix from James Morris.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  LSM: restore certain default error codes

Pull block fixes from Jens Axboe:
 "Two fixes in this pull request:

   - The writeback regression fix from Tejun, which has been weeks in
     the making.  This fixes a case where we would sometimes not issue
     writeback when we should have.

   - An older fix for a memory corruption issue in mtip32xx.  It was
     deferred since we wanted a better fix for this (driver should not
     have to handle that case), but given the timing, it's better to put
     the simple fix in for 4.2 release"

* 'for-linus' of git://git.kernel.dk/linux-block:
  mtip32x: fix regression introduced by blk-mq per-hctx flush
  writeback: sync_inodes_sb() must write out I_DIRTY_TIME inodes and always call wait_sb_inodes()