1. 01 3月, 2011 13 次提交
  2. 13 2月, 2011 2 次提交
    • B
      [SCSI] megaraid_sas: Sanity check user supplied length before passing it to dma_alloc_coherent() · 98cb7e44
      Bjørn Mork 提交于
      The ioc->sgl[i].iov_len value is supplied by the ioctl caller, and can be
      zero in some cases.  Assume that's valid and continue without error.
      
      Fixes (multiple individual reports of the same problem for quite a while):
      
      http://marc.info/?l=linux-ide&m=128941801715301
      http://bugs.debian.org/604627
      http://www.mail-archive.com/linux-poweredge@dell.com/msg02575.html
      
      megasas: Failed to alloc kernel SGL buffer for IOCTL
      
      and
      
      [   69.162538] ------------[ cut here ]------------
      [   69.162806] kernel BUG at /build/buildd/linux-2.6.32/lib/swiotlb.c:368!
      [   69.163134] invalid opcode: 0000 [#1] SMP
      [   69.163570] last sysfs file: /sys/devices/system/cpu/cpu3/cache/index2/shared_cpu_map
      [   69.163975] CPU 0
      [   69.164227] Modules linked in: fbcon tileblit font bitblit softcursor vga16fb vgastate ioatdma radeon ttm drm_kms_helper shpchp drm i2c_algo_bit lp parport floppy pata_jmicron megaraid_sas igb dca
      [   69.167419] Pid: 1206, comm: smartctl Tainted: G        W  2.6.32-25-server #45-Ubuntu X8DTN
      [   69.167843] RIP: 0010:[<ffffffff812c4dc5>]  [<ffffffff812c4dc5>] map_single+0x255/0x260
      [   69.168370] RSP: 0018:ffff88081c0ebc58  EFLAGS: 00010246
      [   69.168655] RAX: 000000000003bffc RBX: 00000000ffffffff RCX: 0000000000000002
      [   69.169000] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88001dffe000
      [   69.169346] RBP: ffff88081c0ebcb8 R08: 0000000000000000 R09: ffff880000030840
      [   69.169691] R10: 0000000000100000 R11: 0000000000000000 R12: 0000000000000000
      [   69.170036] R13: 00000000ffffffff R14: 0000000000000001 R15: 0000000000200000
      [   69.170382] FS:  00007fb8de189720(0000) GS:ffff88001de00000(0000) knlGS:0000000000000000
      [   69.170794] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      [   69.171094] CR2: 00007fb8dd59237c CR3: 000000081a790000 CR4: 00000000000006f0
      [   69.171439] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
      [   69.171784] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
      [   69.172130] Process smartctl (pid: 1206, threadinfo ffff88081c0ea000, task ffff88081a760000)
      [   69.194513] Stack:
      [   69.205788]  0000000000000034 00000002817e3390 0000000000000000 ffff88081c0ebe00
      [   69.217739] <0> 0000000000000000 000000000003bffc 0000000000000000 0000000000000000
      [   69.241250] <0> 0000000000000000 00000000ffffffff ffff88081c5b4080 ffff88081c0ebe00
      [   69.277310] Call Trace:
      [   69.289278]  [<ffffffff812c52ac>] swiotlb_alloc_coherent+0xec/0x130
      [   69.301118]  [<ffffffff81038b31>] x86_swiotlb_alloc_coherent+0x61/0x70
      [   69.313045]  [<ffffffffa002d0ce>] megasas_mgmt_fw_ioctl+0x1ae/0x690 [megaraid_sas]
      [   69.336399]  [<ffffffffa002d748>] megasas_mgmt_ioctl_fw+0x198/0x240 [megaraid_sas]
      [   69.359346]  [<ffffffffa002f695>] megasas_mgmt_ioctl+0x35/0x50 [megaraid_sas]
      [   69.370902]  [<ffffffff81153b12>] vfs_ioctl+0x22/0xa0
      [   69.382322]  [<ffffffff8115da2a>] ? alloc_fd+0x10a/0x150
      [   69.393622]  [<ffffffff81153cb1>] do_vfs_ioctl+0x81/0x410
      [   69.404696]  [<ffffffff8155cc13>] ? do_page_fault+0x153/0x3b0
      [   69.415761]  [<ffffffff811540c1>] sys_ioctl+0x81/0xa0
      [   69.426640]  [<ffffffff810121b2>] system_call_fastpath+0x16/0x1b
      [   69.437491] Code: fe ff ff 48 8b 3d 74 38 76 00 41 bf 00 00 20 00 e8 51 f5 d7 ff 83 e0 ff 48 05 ff 07 00 00 48 c1 e8 0b 48 89 45 c8 e9 13 fe ff ff <0f> 0b eb fe 0f 1f 80 00 00 00 00 55 48 89 e5 48 83 ec 20 4c 89
      [   69.478216] RIP  [<ffffffff812c4dc5>] map_single+0x255/0x260
      [   69.489668]  RSP <ffff88081c0ebc58>
      [   69.500975] ---[ end trace 6a2181b634e2abc7 ]---
      Reported-by: NBokhan Artem <aptem@ngs.ru>
      Reported by: Marc-Christian Petersen <m.c.p@gmx.de>
      Signed-off-by: NBjørn Mork <bjorn@mork.no>
      Cc: "Benz, Michael" <Michael.Benz@lsi.com>
      Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>
      98cb7e44
    • T
      [SCSI] remove flush_scheduled_work() usages · a684b8da
      Tejun Heo 提交于
      Simple conversions to drop flush_scheduled_work() usages in
      drivers/scsi.  More involved ones will be done in separate patches.
      
      * NCR5380, megaraid_sas: cancel_delayed_work() +
        flush_scheduled_work() -> cancel_delayed_work_sync().
      
      * mpt2sas_scsih: drop unnecessary flush_scheduled_work().
      
      * arcmsr_hba, ipr, pmcraid: flush the used work explicitly instead of
        using flush_scheduled_work().
      Signed-off-by: NTejun Heo <tj@kernel.org>
      Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>
      a684b8da
  3. 23 12月, 2010 4 次提交
  4. 22 12月, 2010 2 次提交
  5. 10 12月, 2010 1 次提交
  6. 17 11月, 2010 1 次提交
    • J
      SCSI host lock push-down · f281233d
      Jeff Garzik 提交于
      Move the mid-layer's ->queuecommand() invocation from being locked
      with the host lock to being unlocked to facilitate speeding up the
      critical path for drivers who don't need this lock taken anyway.
      
      The patch below presents a simple SCSI host lock push-down as an
      equivalent transformation.  No locking or other behavior should change
      with this patch.  All existing bugs and locking orders are preserved.
      
      Additionally, add one parameter to queuecommand,
      	struct Scsi_Host *
      and remove one parameter from queuecommand,
      	void (*done)(struct scsi_cmnd *)
      
      Scsi_Host* is a convenient pointer that most host drivers need anyway,
      and 'done' is redundant to struct scsi_cmnd->scsi_done.
      
      Minimal code disturbance was attempted with this change.  Most drivers
      needed only two one-line modifications for their host lock push-down.
      Signed-off-by: NJeff Garzik <jgarzik@redhat.com>
      Acked-by: NJames Bottomley <James.Bottomley@suse.de>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f281233d
  7. 27 10月, 2010 4 次提交
  8. 15 10月, 2010 1 次提交
    • A
      llseek: automatically add .llseek fop · 6038f373
      Arnd Bergmann 提交于
      All file_operations should get a .llseek operation so we can make
      nonseekable_open the default for future file operations without a
      .llseek pointer.
      
      The three cases that we can automatically detect are no_llseek, seq_lseek
      and default_llseek. For cases where we can we can automatically prove that
      the file offset is always ignored, we use noop_llseek, which maintains
      the current behavior of not returning an error from a seek.
      
      New drivers should normally not use noop_llseek but instead use no_llseek
      and call nonseekable_open at open time.  Existing drivers can be converted
      to do the same when the maintainer knows for certain that no user code
      relies on calling seek on the device file.
      
      The generated code is often incorrectly indented and right now contains
      comments that clarify for each added line why a specific variant was
      chosen. In the version that gets submitted upstream, the comments will
      be gone and I will manually fix the indentation, because there does not
      seem to be a way to do that using coccinelle.
      
      Some amount of new code is currently sitting in linux-next that should get
      the same modifications, which I will do at the end of the merge window.
      
      Many thanks to Julia Lawall for helping me learn to write a semantic
      patch that does all this.
      
      ===== begin semantic patch =====
      // This adds an llseek= method to all file operations,
      // as a preparation for making no_llseek the default.
      //
      // The rules are
      // - use no_llseek explicitly if we do nonseekable_open
      // - use seq_lseek for sequential files
      // - use default_llseek if we know we access f_pos
      // - use noop_llseek if we know we don't access f_pos,
      //   but we still want to allow users to call lseek
      //
      @ open1 exists @
      identifier nested_open;
      @@
      nested_open(...)
      {
      <+...
      nonseekable_open(...)
      ...+>
      }
      
      @ open exists@
      identifier open_f;
      identifier i, f;
      identifier open1.nested_open;
      @@
      int open_f(struct inode *i, struct file *f)
      {
      <+...
      (
      nonseekable_open(...)
      |
      nested_open(...)
      )
      ...+>
      }
      
      @ read disable optional_qualifier exists @
      identifier read_f;
      identifier f, p, s, off;
      type ssize_t, size_t, loff_t;
      expression E;
      identifier func;
      @@
      ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
      {
      <+...
      (
         *off = E
      |
         *off += E
      |
         func(..., off, ...)
      |
         E = *off
      )
      ...+>
      }
      
      @ read_no_fpos disable optional_qualifier exists @
      identifier read_f;
      identifier f, p, s, off;
      type ssize_t, size_t, loff_t;
      @@
      ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
      {
      ... when != off
      }
      
      @ write @
      identifier write_f;
      identifier f, p, s, off;
      type ssize_t, size_t, loff_t;
      expression E;
      identifier func;
      @@
      ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
      {
      <+...
      (
        *off = E
      |
        *off += E
      |
        func(..., off, ...)
      |
        E = *off
      )
      ...+>
      }
      
      @ write_no_fpos @
      identifier write_f;
      identifier f, p, s, off;
      type ssize_t, size_t, loff_t;
      @@
      ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
      {
      ... when != off
      }
      
      @ fops0 @
      identifier fops;
      @@
      struct file_operations fops = {
       ...
      };
      
      @ has_llseek depends on fops0 @
      identifier fops0.fops;
      identifier llseek_f;
      @@
      struct file_operations fops = {
      ...
       .llseek = llseek_f,
      ...
      };
      
      @ has_read depends on fops0 @
      identifier fops0.fops;
      identifier read_f;
      @@
      struct file_operations fops = {
      ...
       .read = read_f,
      ...
      };
      
      @ has_write depends on fops0 @
      identifier fops0.fops;
      identifier write_f;
      @@
      struct file_operations fops = {
      ...
       .write = write_f,
      ...
      };
      
      @ has_open depends on fops0 @
      identifier fops0.fops;
      identifier open_f;
      @@
      struct file_operations fops = {
      ...
       .open = open_f,
      ...
      };
      
      // use no_llseek if we call nonseekable_open
      ////////////////////////////////////////////
      @ nonseekable1 depends on !has_llseek && has_open @
      identifier fops0.fops;
      identifier nso ~= "nonseekable_open";
      @@
      struct file_operations fops = {
      ...  .open = nso, ...
      +.llseek = no_llseek, /* nonseekable */
      };
      
      @ nonseekable2 depends on !has_llseek @
      identifier fops0.fops;
      identifier open.open_f;
      @@
      struct file_operations fops = {
      ...  .open = open_f, ...
      +.llseek = no_llseek, /* open uses nonseekable */
      };
      
      // use seq_lseek for sequential files
      /////////////////////////////////////
      @ seq depends on !has_llseek @
      identifier fops0.fops;
      identifier sr ~= "seq_read";
      @@
      struct file_operations fops = {
      ...  .read = sr, ...
      +.llseek = seq_lseek, /* we have seq_read */
      };
      
      // use default_llseek if there is a readdir
      ///////////////////////////////////////////
      @ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
      identifier fops0.fops;
      identifier readdir_e;
      @@
      // any other fop is used that changes pos
      struct file_operations fops = {
      ... .readdir = readdir_e, ...
      +.llseek = default_llseek, /* readdir is present */
      };
      
      // use default_llseek if at least one of read/write touches f_pos
      /////////////////////////////////////////////////////////////////
      @ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
      identifier fops0.fops;
      identifier read.read_f;
      @@
      // read fops use offset
      struct file_operations fops = {
      ... .read = read_f, ...
      +.llseek = default_llseek, /* read accesses f_pos */
      };
      
      @ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
      identifier fops0.fops;
      identifier write.write_f;
      @@
      // write fops use offset
      struct file_operations fops = {
      ... .write = write_f, ...
      +	.llseek = default_llseek, /* write accesses f_pos */
      };
      
      // Use noop_llseek if neither read nor write accesses f_pos
      ///////////////////////////////////////////////////////////
      
      @ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
      identifier fops0.fops;
      identifier read_no_fpos.read_f;
      identifier write_no_fpos.write_f;
      @@
      // write fops use offset
      struct file_operations fops = {
      ...
       .write = write_f,
       .read = read_f,
      ...
      +.llseek = noop_llseek, /* read and write both use no f_pos */
      };
      
      @ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
      identifier fops0.fops;
      identifier write_no_fpos.write_f;
      @@
      struct file_operations fops = {
      ... .write = write_f, ...
      +.llseek = noop_llseek, /* write uses no f_pos */
      };
      
      @ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
      identifier fops0.fops;
      identifier read_no_fpos.read_f;
      @@
      struct file_operations fops = {
      ... .read = read_f, ...
      +.llseek = noop_llseek, /* read uses no f_pos */
      };
      
      @ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
      identifier fops0.fops;
      @@
      struct file_operations fops = {
      ...
      +.llseek = noop_llseek, /* no read or write fn */
      };
      ===== End semantic patch =====
      Signed-off-by: NArnd Bergmann <arnd@arndb.de>
      Cc: Julia Lawall <julia@diku.dk>
      Cc: Christoph Hellwig <hch@infradead.org>
      6038f373
  9. 08 10月, 2010 1 次提交
    • B
      [SCSI] megaraid_sas: Add Online Controller Reset to MegaRAID SAS drive · 39a98554
      bo yang 提交于
      To add the Online controller reset support, driver need to do:
      a). reset the controller chips -- Xscale and Gen2 which will change
      the function calls and add the reset function related to this two
      chips.
      b). during the reset, driver will store the pending cmds which not
      returned by FW to driver's pending queue.  Driver will re-issue those
      pending cmds again to FW after the OCR finished.
      c). In driver's timeout routine, driver will report to OS as reset.
      Also driver's queue routine will block the cmds until the OCR
      finished.
      d). in Driver's ISR routine, if driver get the FW state as state
      change, FW in Failure status and FW support online controller
      reset (OCR), driver will start to do the controller reset.
      e). In driver's IOCTL routine, the application cmds will wait for the
      OCR to finish, then issue the cmds to FW.
      
      Signed-off-by Bo Yang <bo.yang@lsi.com>
      Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>
      39a98554
  10. 16 9月, 2010 1 次提交
    • A
      scsi: autoconvert trivial BKL users to private mutex · c45d15d2
      Arnd Bergmann 提交于
      All these files use the big kernel lock in a trivial
      way to serialize their private file operations,
      typically resulting from an earlier semi-automatic
      pushdown from VFS.
      
      None of these drivers appears to want to lock against
      other code, and they all use the BKL as the top-level
      lock in their file operations, meaning that there
      is no lock-order inversion problem.
      
      Consequently, we can remove the BKL completely,
      replacing it with a per-file mutex in every case.
      Using a scripted approach means we can avoid
      typos.
      
      file=$1
      name=$2
      if grep -q lock_kernel ${file} ; then
          if grep -q 'include.*linux.mutex.h' ${file} ; then
                  sed -i '/include.*<linux\/smp_lock.h>/d' ${file}
          else
                  sed -i 's/include.*<linux\/smp_lock.h>.*$/include <linux\/mutex.h>/g' ${file}
          fi
          sed -i ${file} \
              -e "/^#include.*linux.mutex.h/,$ {
                      1,/^\(static\|int\|long\)/ {
                           /^\(static\|int\|long\)/istatic DEFINE_MUTEX(${name}_mutex);
      
      } }"  \
          -e "s/\(un\)*lock_kernel\>[ ]*()/mutex_\1lock(\&${name}_mutex)/g" \
          -e '/[      ]*cycle_kernel_lock();/d'
      else
          sed -i -e '/include.*\<smp_lock.h\>/d' ${file}  \
                      -e '/cycle_kernel_lock()/d'
      fi
      Signed-off-by: NArnd Bergmann <arnd@arndb.de>
      Cc: linux-scsi@vger.kernel.org
      Cc: "James E.J. Bottomley" <James.Bottomley@suse.de>
      c45d15d2
  11. 17 5月, 2010 1 次提交
  12. 30 3月, 2010 1 次提交
    • T
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking... · 5a0e3ad6
      Tejun Heo 提交于
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
      
      percpu.h is included by sched.h and module.h and thus ends up being
      included when building most .c files.  percpu.h includes slab.h which
      in turn includes gfp.h making everything defined by the two files
      universally available and complicating inclusion dependencies.
      
      percpu.h -> slab.h dependency is about to be removed.  Prepare for
      this change by updating users of gfp and slab facilities include those
      headers directly instead of assuming availability.  As this conversion
      needs to touch large number of source files, the following script is
      used as the basis of conversion.
      
        http://userweb.kernel.org/~tj/misc/slabh-sweep.py
      
      The script does the followings.
      
      * Scan files for gfp and slab usages and update includes such that
        only the necessary includes are there.  ie. if only gfp is used,
        gfp.h, if slab is used, slab.h.
      
      * When the script inserts a new include, it looks at the include
        blocks and try to put the new include such that its order conforms
        to its surrounding.  It's put in the include block which contains
        core kernel includes, in the same order that the rest are ordered -
        alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
        doesn't seem to be any matching order.
      
      * If the script can't find a place to put a new include (mostly
        because the file doesn't have fitting include block), it prints out
        an error message indicating which .h file needs to be added to the
        file.
      
      The conversion was done in the following steps.
      
      1. The initial automatic conversion of all .c files updated slightly
         over 4000 files, deleting around 700 includes and adding ~480 gfp.h
         and ~3000 slab.h inclusions.  The script emitted errors for ~400
         files.
      
      2. Each error was manually checked.  Some didn't need the inclusion,
         some needed manual addition while adding it to implementation .h or
         embedding .c file was more appropriate for others.  This step added
         inclusions to around 150 files.
      
      3. The script was run again and the output was compared to the edits
         from #2 to make sure no file was left behind.
      
      4. Several build tests were done and a couple of problems were fixed.
         e.g. lib/decompress_*.c used malloc/free() wrappers around slab
         APIs requiring slab.h to be added manually.
      
      5. The script was run on all .h files but without automatically
         editing them as sprinkling gfp.h and slab.h inclusions around .h
         files could easily lead to inclusion dependency hell.  Most gfp.h
         inclusion directives were ignored as stuff from gfp.h was usually
         wildly available and often used in preprocessor macros.  Each
         slab.h inclusion directive was examined and added manually as
         necessary.
      
      6. percpu.h was updated not to include slab.h.
      
      7. Build test were done on the following configurations and failures
         were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
         distributed build env didn't work with gcov compiles) and a few
         more options had to be turned off depending on archs to make things
         build (like ipr on powerpc/64 which failed due to missing writeq).
      
         * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
         * powerpc and powerpc64 SMP allmodconfig
         * sparc and sparc64 SMP allmodconfig
         * ia64 SMP allmodconfig
         * s390 SMP allmodconfig
         * alpha SMP allmodconfig
         * um on x86_64 SMP allmodconfig
      
      8. percpu.h modifications were reverted so that it could be applied as
         a separate patch and serve as bisection point.
      
      Given the fact that I had only a couple of failures from tests on step
      6, I'm fairly confident about the coverage of this conversion patch.
      If there is a breakage, it's likely to be something in one of the arch
      headers which should be easily discoverable easily on most builds of
      the specific arch.
      Signed-off-by: NTejun Heo <tj@kernel.org>
      Guess-its-ok-by: NChristoph Lameter <cl@linux-foundation.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
      5a0e3ad6
  13. 20 2月, 2010 1 次提交
  14. 18 2月, 2010 4 次提交
  15. 13 1月, 2010 1 次提交
  16. 10 12月, 2009 1 次提交
    • N
      [SCSI] megaraid_sas: make driver PCI legacy I/O port free driver · aeab3fd7
      Noriyuki Fujii 提交于
      On the large servers, I/O port resource may not be assigned to all
      the PCI devices since it is limited (to 64KB on Intel Architecture[1])
      and it may also be fragmented (I/O base register of PCI-to-PCI bridge
      will usually be aligned to a 4KB boundary[2]).
      If no I/O port resource is assigned to devices, those devices do not
      work.
      
      [1] Some machines support 64KB I/O port space per PCI segment.
      [2] Some P2P bridges support optional 1KB aligned I/O base.
      
      Therefore, I made a patch for MegaRAID SAS driver to make PCI legacy
      I/O port free.  I have also tested the patch and it had no problem.
      
      The way to make PCI legacy I/O port free is the same as Fusion-MPT
      driver's and it has been merged into 2.6.30.4.
      
      This has already been fixed in e1000 and lpfc.
      
      As a result of the above, the driver can handle its device even when
      there are a huge number of PCI devices being used on the system and no
      I/O port region assigned to the device.
      Signed-off-by: NNoriyuki Fujii <n-fujii@np.css.fujitsu.com>
      Acked-by: N"Yang, Bo" <Bo.Yang@lsi.com>
      Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>
      aeab3fd7
  17. 05 12月, 2009 1 次提交
    • M
      [SCSI] modify change_queue_depth to take in reason why it is being called · e881a172
      Mike Christie 提交于
      This patch modifies scsi_host_template->change_queue_depth so that
      it takes an argument indicating why it is being called. This will be
      used so that if a LLD needs to do some extra processing when
      handling queue fulls or later ramp ups, it can do so.
      
      This is a simple port of the drivers setting a change_queue_depth
      callback. In the patch I just have these LLDs adjust the queue depth
      if the user was requesting it.
      Signed-off-by: NMike Christie <michaelc@cs.wisc.edu>
      
      [Vasu.Dev: v2
      	Also converted pmcraid_change_queue_depth and then verified
      all modules compile  using "make allmodconfig" for any new build
      warnings on X86_64.
      
      	Updated original description after combing two original
      patches from Mike to make this patch git bisectable.]
      Signed-off-by: NVasu Dev <vasu.dev@intel.com>
      [jejb: fixed up 53c700]
      Signed-off-by: NJames Bottomley <James.Bottomley@suse.de>
      e881a172