1. 22 10月, 2015 3 次提交
  2. 11 9月, 2015 1 次提交
  3. 29 7月, 2015 1 次提交
    • C
      block: add a bi_error field to struct bio · 4246a0b6
      Christoph Hellwig 提交于
      Currently we have two different ways to signal an I/O error on a BIO:
      
       (1) by clearing the BIO_UPTODATE flag
       (2) by returning a Linux errno value to the bi_end_io callback
      
      The first one has the drawback of only communicating a single possible
      error (-EIO), and the second one has the drawback of not beeing persistent
      when bios are queued up, and are not passed along from child to parent
      bio in the ever more popular chaining scenario.  Having both mechanisms
      available has the additional drawback of utterly confusing driver authors
      and introducing bugs where various I/O submitters only deal with one of
      them, and the others have to add boilerplate code to deal with both kinds
      of error returns.
      
      So add a new bi_error field to store an errno value directly in struct
      bio and remove the existing mechanisms to clean all this up.
      Signed-off-by: NChristoph Hellwig <hch@lst.de>
      Reviewed-by: NHannes Reinecke <hare@suse.de>
      Reviewed-by: NNeilBrown <neilb@suse.com>
      Signed-off-by: NJens Axboe <axboe@fb.com>
      4246a0b6
  4. 07 7月, 2015 1 次提交
    • M
      bio integrity: do not assume bio_integrity_pool exists if bioset exists · bb8bd38b
      Mike Snitzer 提交于
      bio_integrity_alloc() and bio_integrity_free() assume that if a bio was
      allocated from a bioset that that bioset also had its bio_integrity_pool
      allocated using bioset_integrity_create().  This is a very bad
      assumption given that bioset_create() and bioset_integrity_create() are
      completely disjoint.  Not all callers of bioset_create() have been
      trained to also call bioset_integrity_create() -- and they may not care
      to be.
      
      Fix this by falling back to kmalloc'ing 'struct bio_integrity_payload'
      rather than force all bioset consumers to (wastefully) preallocate a
      bio_integrity_pool that they very likely won't actually need (given the
      niche nature of the current block integrity support).
      
      Otherwise, a NULL pointer "Kernel BUG" with a trace like the following
      will be observed (as seen on s390x using zfcp storage) because dm-io
      doesn't use bioset_integrity_create() when creating its bioset:
      
          [  791.643338] Call Trace:
          [  791.643339] ([<00000003df98b848>] 0x3df98b848)
          [  791.643341]  [<00000000002c5de8>] bio_integrity_alloc+0x48/0xf8
          [  791.643348]  [<00000000002c6486>] bio_integrity_prep+0xae/0x2f0
          [  791.643349]  [<0000000000371e38>] blk_queue_bio+0x1c8/0x3d8
          [  791.643355]  [<000000000036f8d0>] generic_make_request+0xc0/0x100
          [  791.643357]  [<000000000036f9b2>] submit_bio+0xa2/0x198
          [  791.643406]  [<000003ff801f9774>] dispatch_io+0x15c/0x3b0 [dm_mod]
          [  791.643419]  [<000003ff801f9b3e>] dm_io+0x176/0x2f0 [dm_mod]
          [  791.643423]  [<000003ff8074b28a>] do_reads+0x13a/0x1a8 [dm_mirror]
          [  791.643425]  [<000003ff8074b43a>] do_mirror+0x142/0x298 [dm_mirror]
          [  791.643428]  [<0000000000154fca>] process_one_work+0x18a/0x3f8
          [  791.643432]  [<000000000015598a>] worker_thread+0x132/0x3b0
          [  791.643435]  [<000000000015d49a>] kthread+0xd2/0xd8
          [  791.643438]  [<00000000005bc0ca>] kernel_thread_starter+0x6/0xc
          [  791.643446]  [<00000000005bc0c4>] kernel_thread_starter+0x0/0xc
      Signed-off-by: NMike Snitzer <snitzer@redhat.com>
      Cc: stable@vger.kernel.org
      Signed-off-by: NJens Axboe <axboe@fb.com>
      bb8bd38b
  5. 22 5月, 2015 1 次提交
    • M
      block: remove management of bi_remaining when restoring original bi_end_io · 326e1dbb
      Mike Snitzer 提交于
      Commit c4cf5261 ("bio: skip atomic inc/dec of ->bi_remaining for
      non-chains") regressed all existing callers that followed this pattern:
       1) saving a bio's original bi_end_io
       2) wiring up an intermediate bi_end_io
       3) restoring the original bi_end_io from intermediate bi_end_io
       4) calling bio_endio() to execute the restored original bi_end_io
      
      The regression was due to BIO_CHAIN only ever getting set if
      bio_inc_remaining() is called.  For the above pattern it isn't set until
      step 3 above (step 2 would've needed to establish BIO_CHAIN).  As such
      the first bio_endio(), in step 2 above, never decremented __bi_remaining
      before calling the intermediate bi_end_io -- leaving __bi_remaining with
      the value 1 instead of 0.  When bio_inc_remaining() occurred during step
      3 it brought it to a value of 2.  When the second bio_endio() was
      called, in step 4 above, it should've called the original bi_end_io but
      it didn't because there was an extra reference that wasn't dropped (due
      to atomic operations being optimized away since BIO_CHAIN wasn't set
      upfront).
      
      Fix this issue by removing the __bi_remaining management complexity for
      all callers that use the above pattern -- bio_chain() is the only
      interface that _needs_ to be concerned with __bi_remaining.  For the
      above pattern callers just expect the bi_end_io they set to get called!
      Remove bio_endio_nodec() and also remove all bio_inc_remaining() calls
      that aren't associated with the bio_chain() interface.
      
      Also, the bio_inc_remaining() interface has been moved local to bio.c.
      
      Fixes: c4cf5261 ("bio: skip atomic inc/dec of ->bi_remaining for non-chains")
      Reviewed-by: NChristoph Hellwig <hch@lst.de>
      Reviewed-by: NJan Kara <jack@suse.cz>
      Signed-off-by: NMike Snitzer <snitzer@redhat.com>
      Signed-off-by: NJens Axboe <axboe@fb.com>
      326e1dbb
  6. 02 12月, 2014 1 次提交
    • D
      block: fix regression where bio_integrity_process uses wrong bio_vec iterator · 594416a7
      Darrick J. Wong 提交于
      bio integrity handling is broken on a system with LVM layered atop a
      DIF/DIX SCSI drive because device mapper clones the bio, modifies the
      clone, and sends the clone to the lower layers for processing.
      However, the clone bio has bi_vcnt == 0, which means that when the sd
      driver calls bio_integrity_process to attach DIX data, the
      for_each_segment_all() call (which uses bi_vcnt) returns immediately
      and random garbage is sent to the disk on a disk write.  The disk of
      course returns an error.
      
      Therefore, teach bio_integrity_process() to use bio_for_each_segment()
      to iterate the bio_vecs, since the per-bio iterator tracks which
      bio_vecs are associated with that particular bio.  The integrity
      handling code is effectively part of the "driver" (it's not the bio
      owner), so it must use the correct iterator function.
      
      v2: Fix a compiler warning about abandoned local variables.  This
      patch supersedes "block: bio_integrity_process uses wrong bio_vec
      iterator".  Patch applies against 3.18-rc6.
      Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      Acked-by: NMartin K. Petersen <martin.petersen@oracle.com>
      Signed-off-by: NJens Axboe <axboe@fb.com>
      594416a7
  7. 14 10月, 2014 1 次提交
  8. 27 9月, 2014 10 次提交
  9. 22 8月, 2014 1 次提交
  10. 02 7月, 2014 1 次提交
    • G
      bio-integrity: add "bip_max_vcnt" into struct bio_integrity_payload · cbcd1054
      Gu Zheng 提交于
      Commit 08778795 ("block: Fix nr_vecs for inline integrity vectors") from
      Martin introduces the function bip_integrity_vecs(get the useful vectors)
      to fix the issue about nr_vecs for inline integrity vectors that reported
      by David Milburn.
      
      But it seems that bip_integrity_vecs() will return the wrong number if the
      bio is not based on any bio_set for some reason(bio->bi_pool == NULL),
      because in that case, the bip_inline_vecs[0] is malloced directly.  So
      here we add the bip_max_vcnt to record the count of vector slots, and
      cleanup the function bip_integrity_vecs().
      Signed-off-by: NGu Zheng <guz.fnst@cn.fujitsu.com>
      Cc: Martin K. Petersen <martin.petersen@oracle.com>
      Cc: Kent Overstreet <kmo@daterainc.com>
      Signed-off-by: NJens Axboe <axboe@fb.com>
      cbcd1054
  11. 19 5月, 2014 1 次提交
  12. 23 4月, 2014 1 次提交
  13. 09 4月, 2014 2 次提交
  14. 22 2月, 2014 2 次提交
  15. 10 2月, 2014 1 次提交
  16. 08 2月, 2014 1 次提交
  17. 22 1月, 2014 1 次提交
    • N
      bio-integrity: Fix bio_integrity_verify segment start bug · 5837c80e
      Nicholas Bellinger 提交于
      This patch addresses a bug in bio_integrity_verify() code that has
      been causing DIF READ verify operations to be silently skipped.
      
      The issue is that bio->bi_idx will have been incremented within
      bio_advance() code in the normal blk_update_request() ->
      req_bio_endio() completion path, and bio_integrity_verify() is
      using bio_for_each_segment() which starts the bio segment walk
      at the current bio->bi_idx.
      
      So instead use bio_for_each_segment_all() to always start the bio
      segment walk from zero, regardless of the current bio->bi_idx
      value after bio_advance() has been called.
      
      Cc: Martin K. Petersen <martin.petersen@oracle.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Christoph Hellwig <hch@lst.de>
      Signed-off-by: NNicholas Bellinger <nab@linux-iscsi.org>
      Cc: stable@kernel.dk # >= v3.10
      Signed-off-by: NJens Axboe <axboe@kernel.dk>
      5837c80e
  18. 24 11月, 2013 5 次提交
    • K
      block: Kill bio_pair_split() · 4b1faf93
      Kent Overstreet 提交于
      Signed-off-by: NKent Overstreet <kmo@daterainc.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      4b1faf93
    • K
      block: Generic bio chaining · 196d38bc
      Kent Overstreet 提交于
      This adds a generic mechanism for chaining bio completions. This is
      going to be used for a bio_split() replacement, and it turns out to be
      very useful in a fair amount of driver code - a fair number of drivers
      were implementing this in their own roundabout ways, often painfully.
      
      Note that this means it's no longer to call bio_endio() more than once
      on the same bio! This can cause problems for drivers that save/restore
      bi_end_io. Arguably they shouldn't be saving/restoring bi_end_io at all
      - in all but the simplest cases they'd be better off just cloning the
      bio, and immutable biovecs is making bio cloning cheaper. But for now,
      we add a bio_endio_nodec() for these cases.
      Signed-off-by: NKent Overstreet <kmo@daterainc.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      196d38bc
    • K
      bio-integrity: Convert to bvec_iter · d57a5f7c
      Kent Overstreet 提交于
      The bio integrity is also stored in a bvec array, so if we use the bvec
      iter code we just added, the integrity code won't need to implement its
      own iteration stuff (bio_integrity_mark_head(), bio_integrity_mark_tail())
      Signed-off-by: NKent Overstreet <kmo@daterainc.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
      Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
      d57a5f7c
    • K
      block: Convert bio_for_each_segment() to bvec_iter · 7988613b
      Kent Overstreet 提交于
      More prep work for immutable biovecs - with immutable bvecs drivers
      won't be able to use the biovec directly, they'll need to use helpers
      that take into account bio->bi_iter.bi_bvec_done.
      
      This updates callers for the new usage without changing the
      implementation yet.
      Signed-off-by: NKent Overstreet <kmo@daterainc.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: "Ed L. Cashin" <ecashin@coraid.com>
      Cc: Nick Piggin <npiggin@kernel.dk>
      Cc: Lars Ellenberg <drbd-dev@lists.linbit.com>
      Cc: Jiri Kosina <jkosina@suse.cz>
      Cc: Paul Clements <Paul.Clements@steeleye.com>
      Cc: Jim Paris <jim@jtan.com>
      Cc: Geoff Levand <geoff@infradead.org>
      Cc: Yehuda Sadeh <yehuda@inktank.com>
      Cc: Sage Weil <sage@inktank.com>
      Cc: Alex Elder <elder@inktank.com>
      Cc: ceph-devel@vger.kernel.org
      Cc: Joshua Morris <josh.h.morris@us.ibm.com>
      Cc: Philip Kelleher <pjk1939@linux.vnet.ibm.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Jeremy Fitzhardinge <jeremy@goop.org>
      Cc: Neil Brown <neilb@suse.de>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: linux390@de.ibm.com
      Cc: Nagalakshmi Nandigama <Nagalakshmi.Nandigama@lsi.com>
      Cc: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
      Cc: support@lsi.com
      Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Cc: Steven Whitehouse <swhiteho@redhat.com>
      Cc: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Guo Chao <yan@linux.vnet.ibm.com>
      Cc: Asai Thambi S P <asamymuthupa@micron.com>
      Cc: Selvan Mani <smani@micron.com>
      Cc: Sam Bradshaw <sbradshaw@micron.com>
      Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
      Cc: Keith Busch <keith.busch@intel.com>
      Cc: Stephen Hemminger <shemminger@vyatta.com>
      Cc: Quoc-Son Anh <quoc-sonx.anh@intel.com>
      Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
      Cc: Nitin Gupta <ngupta@vflare.org>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Jerome Marchand <jmarchan@redhat.com>
      Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
      Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
      Cc: Mike Snitzer <snitzer@redhat.com>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: Jan Kara <jack@suse.cz>
      Cc: linux-m68k@lists.linux-m68k.org
      Cc: linuxppc-dev@lists.ozlabs.org
      Cc: drbd-user@lists.linbit.com
      Cc: nbd-general@lists.sourceforge.net
      Cc: cbe-oss-dev@lists.ozlabs.org
      Cc: xen-devel@lists.xensource.com
      Cc: virtualization@lists.linux-foundation.org
      Cc: linux-raid@vger.kernel.org
      Cc: linux-s390@vger.kernel.org
      Cc: DL-MPTFusionLinux@lsi.com
      Cc: linux-scsi@vger.kernel.org
      Cc: devel@driverdev.osuosl.org
      Cc: linux-fsdevel@vger.kernel.org
      Cc: cluster-devel@redhat.com
      Cc: linux-mm@kvack.org
      Acked-by: NGeoff Levand <geoff@infradead.org>
      7988613b
    • K
      block: Abstract out bvec iterator · 4f024f37
      Kent Overstreet 提交于
      Immutable biovecs are going to require an explicit iterator. To
      implement immutable bvecs, a later patch is going to add a bi_bvec_done
      member to this struct; for now, this patch effectively just renames
      things.
      Signed-off-by: NKent Overstreet <kmo@daterainc.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: "Ed L. Cashin" <ecashin@coraid.com>
      Cc: Nick Piggin <npiggin@kernel.dk>
      Cc: Lars Ellenberg <drbd-dev@lists.linbit.com>
      Cc: Jiri Kosina <jkosina@suse.cz>
      Cc: Matthew Wilcox <willy@linux.intel.com>
      Cc: Geoff Levand <geoff@infradead.org>
      Cc: Yehuda Sadeh <yehuda@inktank.com>
      Cc: Sage Weil <sage@inktank.com>
      Cc: Alex Elder <elder@inktank.com>
      Cc: ceph-devel@vger.kernel.org
      Cc: Joshua Morris <josh.h.morris@us.ibm.com>
      Cc: Philip Kelleher <pjk1939@linux.vnet.ibm.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: "Michael S. Tsirkin" <mst@redhat.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Jeremy Fitzhardinge <jeremy@goop.org>
      Cc: Neil Brown <neilb@suse.de>
      Cc: Alasdair Kergon <agk@redhat.com>
      Cc: Mike Snitzer <snitzer@redhat.com>
      Cc: dm-devel@redhat.com
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: linux390@de.ibm.com
      Cc: Boaz Harrosh <bharrosh@panasas.com>
      Cc: Benny Halevy <bhalevy@tonian.com>
      Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Cc: Chris Mason <chris.mason@fusionio.com>
      Cc: "Theodore Ts'o" <tytso@mit.edu>
      Cc: Andreas Dilger <adilger.kernel@dilger.ca>
      Cc: Jaegeuk Kim <jaegeuk.kim@samsung.com>
      Cc: Steven Whitehouse <swhiteho@redhat.com>
      Cc: Dave Kleikamp <shaggy@kernel.org>
      Cc: Joern Engel <joern@logfs.org>
      Cc: Prasad Joshi <prasadjoshi.linux@gmail.com>
      Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
      Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp>
      Cc: Mark Fasheh <mfasheh@suse.com>
      Cc: Joel Becker <jlbec@evilplan.org>
      Cc: Ben Myers <bpm@sgi.com>
      Cc: xfs@oss.sgi.com
      Cc: Steven Rostedt <rostedt@goodmis.org>
      Cc: Frederic Weisbecker <fweisbec@gmail.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Len Brown <len.brown@intel.com>
      Cc: Pavel Machek <pavel@ucw.cz>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
      Cc: Ben Hutchings <ben@decadent.org.uk>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Guo Chao <yan@linux.vnet.ibm.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Asai Thambi S P <asamymuthupa@micron.com>
      Cc: Selvan Mani <smani@micron.com>
      Cc: Sam Bradshaw <sbradshaw@micron.com>
      Cc: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
      Cc: "Roger Pau Monné" <roger.pau@citrix.com>
      Cc: Jan Beulich <jbeulich@suse.com>
      Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
      Cc: Ian Campbell <Ian.Campbell@citrix.com>
      Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
      Cc: Christian Borntraeger <borntraeger@de.ibm.com>
      Cc: Minchan Kim <minchan@kernel.org>
      Cc: Jiang Liu <jiang.liu@huawei.com>
      Cc: Nitin Gupta <ngupta@vflare.org>
      Cc: Jerome Marchand <jmarchand@redhat.com>
      Cc: Joe Perches <joe@perches.com>
      Cc: Peng Tao <tao.peng@emc.com>
      Cc: Andy Adamson <andros@netapp.com>
      Cc: fanchaoting <fanchaoting@cn.fujitsu.com>
      Cc: Jie Liu <jeff.liu@oracle.com>
      Cc: Sunil Mushran <sunil.mushran@gmail.com>
      Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
      Cc: Namjae Jeon <namjae.jeon@samsung.com>
      Cc: Pankaj Kumar <pankaj.km@samsung.com>
      Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
      Cc: Mel Gorman <mgorman@suse.de>6
      4f024f37
  19. 18 9月, 2013 1 次提交
  20. 12 9月, 2013 1 次提交
  21. 24 3月, 2013 3 次提交
    • K
      bio-integrity: Add explicit field for owner of bip_buf · 29ed7813
      Kent Overstreet 提交于
      This was the only real user of BIO_CLONED, which didn't have very clear
      semantics. Convert to its own flag so we can get rid of BIO_CLONED.
      Signed-off-by: NKent Overstreet <koverstreet@google.com>
      CC: Jens Axboe <axboe@kernel.dk>
      CC: Martin K. Petersen <martin.petersen@oracle.com>
      29ed7813
    • K
      block: Change bio_split() to respect the current value of bi_idx · 5b83636a
      Kent Overstreet 提交于
      In the current code bio_split() won't be seeing partially completed bios
      so this doesn't change any behaviour, but this makes the code a bit
      clearer as to what bio_split() actually requires.
      
      The immediate purpose of the patch is removing unnecessary bi_idx
      references, but the end goal is to allow partial completed bios to be
      submitted, which along with immutable biovecs enables effecient bio
      splitting.
      
      Some of the callers were (double) checking that bios could be split, so
      update their checks too.
      Signed-off-by: NKent Overstreet <koverstreet@google.com>
      CC: Jens Axboe <axboe@kernel.dk>
      CC: Lars Ellenberg <drbd-dev@lists.linbit.com>
      CC: Neil Brown <neilb@suse.de>
      CC: Martin K. Petersen <martin.petersen@oracle.com>
      5b83636a
    • K
      block: Convert integrity to bvec_alloc_bs() · 9f060e22
      Kent Overstreet 提交于
      This adds a pointer to the bvec array to struct bio_integrity_payload,
      instead of the bvecs always being inline; then the bvecs are allocated
      with bvec_alloc_bs().
      
      Changed bvec_alloc_bs() and bvec_free_bs() to take a pointer to a
      mempool instead of the bioset, so that bio integrity can use a different
      mempool for its bvecs, and thus avoid a potential deadlock.
      
      This is eventually for immutable bio vecs - immutable bvecs aren't
      useful if we still have to copy them, hence the need for the pointer.
      Less code is always nice too, though.
      
      Also, bio_integrity_alloc() was using fs_bio_set if no bio_set was
      specified. This was wrong - using the bio_set doesn't protect us from
      memory allocation failures, because we just used kmalloc for the
      bio_integrity_payload. But it does introduce the possibility of
      deadlock, if for some reason we weren't supposed to be using fs_bio_set.
      Signed-off-by: NKent Overstreet <koverstreet@google.com>
      CC: Jens Axboe <axboe@kernel.dk>
      CC: Martin K. Petersen <martin.petersen@oracle.com>
      9f060e22