1. 06 Mar, 2012 28 commits
    • Tejun Heo's avatar
      blkcg: unify blkg's for blkcg policies · e8989fae
      Tejun Heo authored
      Currently, blkg is per cgroup-queue-policy combination.  This is
      unnatural and leads to various convolutions in partially used
      duplicate fields in blkg, config / stat access, and general management
      of blkgs.
      This patch make blkg's per cgroup-queue and let them serve all
      policies.  blkgs are now created and destroyed by blkcg core proper.
      This will allow further consolidation of common management logic into
      blkcg core and API with better defined semantics and layering.
      As a transitional step to untangle blkg management, elvswitch and
      policy [de]registration, all blkgs except the root blkg are being shot
      down during elvswitch and bypass.  This patch adds blkg_root_update()
      to update root blkg in place on policy change.  This is hacky and racy
      but should be good enough as interim step until we get locking
      simplified and switch over to proper in-place update for all blkgs.
      -v2: Root blkgs need to be updated on elvswitch too and blkg_alloc()
           comment wasn't updated according to the function change.  Fixed.
           Both pointed out by Vivek.
      -v3: v2 updated blkg_destroy_all() to invoke update_root_blkg_pd() for
           all policies.  This freed root pd during elvswitch before the
           last queue finished exiting and led to oops.  Directly invoke
           update_root_blkg_pd() only on BLKIO_POLICY_PROP from
           cfq_exit_queue().  This also is closer to what will be done with
           proper in-place blkg update.  Reported by Vivek.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: let blkcg core manage per-queue blkg list and counter · 03aa264a
      Tejun Heo authored
      With the previous patch to move blkg list heads and counters to
      request_queue and blkg, logic to manage them in both policies are
      almost identical and can be moved to blkcg core.
      This patch moves blkg link logic into blkg_lookup_create(), implements
      common blkg unlink code in blkg_destroy(), and updates
      blkg_destory_all() so that it's policy specific and can skip root
      group.  The updated blkg_destroy_all() is now used to both clear queue
      for bypassing and elv switching, and release all blkgs on q exit.
      This patch introduces a race window where policy [de]registration may
      race against queue blkg clearing.  This can only be a problem on cfq
      unload and shouldn't be a real problem in practice (and we have many
      other places where this race already exists).  Future patches will
      remove these unlikely races.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: move per-queue blkg list heads and counters to queue and blkg · 4eef3049
      Tejun Heo authored
      Currently, specific policy implementations are responsible for
      maintaining list and number of blkgs.  This duplicates code
      unnecessarily, and hinders factoring common code and providing blkcg
      API with better defined semantics.
      After this patch, request_queue hosts list heads and counters and blkg
      has list nodes for both policies.  This patch only relocates the
      necessary fields and the next patch will actually move management code
      into blkcg core.
      Note that request_queue->blkg_list[] and ->nr_blkgs[] are hardcoded to
      have 2 elements.  This is to avoid include dependency and will be
      removed by the next patch.
      This patch doesn't introduce any behavior change.
      -v2: Now unnecessary conditional on CONFIG_BLK_CGROUP_MODULE removed
           as pointed out by Vivek.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: don't use blkg->plid in stat related functions · c1768268
      Tejun Heo authored
      blkg is scheduled to be unified for all policies and thus there won't
      be one-to-one mapping from blkg to policy.  Update stat related
      functions to take explicit @pol or @plid arguments and not use
      This is painful for now but most of specific stat interface functions
      will be replaced with a handful of generic helpers.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: make blkg->pd an array and move configuration and stats into it · 549d3aa8
      Tejun Heo authored
      To prepare for unifying blkgs for different policies, make blkg->pd an
      array with BLKIO_NR_POLICIES elements and move blkg->conf, ->stats,
      and ->stats_cpu into blkg_policy_data.
      This patch doesn't introduce any functional difference.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: move refcnt to blkcg core · 1adaf3dd
      Tejun Heo authored
      Currently, blkcg policy implementations manage blkg refcnt duplicating
      mostly identical code in both policies.  This patch moves refcnt to
      blkg and let blkcg core handle refcnt and freeing of blkgs.
      * cfq blkgs now also get freed via RCU.
      * cfq blkgs lose RB_EMPTY_ROOT() sanity check on blkg free.  If
        necessary, we can add blkio_exit_group_fn() to resurrect this.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: let blkcg core handle policy private data allocation · 0381411e
      Tejun Heo authored
      Currently, blkg's are embedded in private data blkcg policy private
      data structure and thus allocated and freed by policies.  This leads
      to duplicate codes in policies, hinders implementing common part in
      blkcg core with strong semantics, and forces duplicate blkg's for the
      same cgroup-q association.
      This patch introduces struct blkg_policy_data which is a separate data
      structure chained from blkg.  Policies specifies the amount of private
      data it needs in its blkio_policy_type->pdata_size and blkcg core
      takes care of allocating them along with blkg which can be accessed
      using blkg_to_pdata().  blkg can be determined from pdata using
      pdata_to_blkg().  blkio_alloc_group_fn() method is accordingly updated
      to blkio_init_group_fn().
      For consistency, tg_of_blkg() and cfqg_of_blkg() are replaced with
      blkg_to_tg() and blkg_to_cfqg() respectively, and functions to map in
      the reverse direction are added.
      Except that policy specific data now lives in a separate data
      structure from blkg, this patch doesn't introduce any functional
      This will be used to unify blkg's for different policies.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: clear all request_queues on blkcg policy [un]registrations · 923adde1
      Tejun Heo authored
      Keep track of all request_queues which have blkcg initialized and turn
      on bypass and invoke blkcg_clear_queue() on all before making changes
      to blkcg policies.
      This is to prepare for moving blkg management into blkcg core.  Note
      that this uses more brute force than necessary.  Finer grained shoot
      down will be implemented later and given that policy [un]registration
      almost never happens on running systems (blk-throtl can't be built as
      a module and cfq usually is the builtin default iosched), this
      shouldn't be a problem for the time being.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: add blkcg_{init|drain|exit}_queue() · 5efd6113
      Tejun Heo authored
      Currently block core calls directly into blk-throttle for init, drain
      and exit.  This patch adds blkcg_{init|drain|exit}_queue() which wraps
      the blk-throttle functions.  This is to give more control and
      visiblity to blkcg core layer for proper layering.  Further patches
      will add logic common to blkcg policies to the functions.
      While at it, collapse blk_throtl_release() into blk_throtl_exit().
      There's no reason to keep them separate.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: let blkio_group point to blkio_cgroup directly · 7ee9c562
      Tejun Heo authored
      Currently, blkg points to the associated blkcg via its css_id.  This
      unnecessarily complicates dereferencing blkcg.  Let blkg hold a
      reference to the associated blkcg and point directly to it and disable
      css_id on blkio_subsys.
      This change requires splitting blkiocg_destroy() into
      blkiocg_pre_destroy() and blkiocg_destroy() so that all blkg's can be
      destroyed and all the blkcg references held by them dropped during
      cgroup removal.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Vivek Goyal's avatar
      blkcg: skip blkg printing if q isn't associated with disk · 92616b5b
      Vivek Goyal authored
      blk-cgroup printing code currently assumes that there is a device/disk
      associated with every queue in the system, but modules like floppy,
      can instantiate request queues without registering disk which can lead
      to oops.
      Skip the queue/blkg which don't have dev/disk associated with them.
      -tj: Factored out backing_dev_info check into blkg_dev_name().
      Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: kill the mind-bending blkg->dev · 7a4dd281
      Tejun Heo authored
      blkg->dev is dev_t recording the device number of the block device for
      the associated request_queue.  It is used to identify the associated
      block device when printing out configuration or stats.
      This is redundant to begin with.  A blkg is an association between a
      cgroup and a request_queue and it of course is possible to reach
      request_queue from blkg and synchronization conventions are in place
      for safe q dereferencing, so this shouldn't be necessary from the
      beginning.  Furthermore, it's initialized by sscanf()ing the device
      name of backing_dev_info.  The mind boggles.
      Anyways, if blkg is visible under rcu lock, we *know* that the
      associated request_queue hasn't gone away yet and its bdi is
      registered and alive - blkg can't be created for request_queue which
      hasn't been fully initialized and it can't go away before blkg is
      Let stat and conf read functions get device name from
      blkg->q->backing_dev_info.dev and pass it down to printing functions
      and remove blkg->dev.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: kill blkio_policy_node · 4bfd482e
      Tejun Heo authored
      Now that blkcg configuration lives in blkg's, blkio_policy_node is no
      longer necessary.  Kill it.
      blkio_policy_parse_and_set() now fails if invoked for missing device
      and functions to print out configurations are updated to print from
      cftype_blkg_same_policy() is dropped along with other policy functions
      for consistency.  Its one line is open coded in the only user -
      -v2: Update to reflect the retry-on-bypass logic change of the
           previous patch.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: don't allow or retain configuration of missing devices · e56da7e2
      Tejun Heo authored
      blkcg is very peculiar in that it allows setting and remembering
      configurations for non-existent devices by maintaining separate data
      structures for configuration.
      This behavior is completely out of the usual norms and outright
      confusing; furthermore, it uses dev_t number to match the
      configuration to devices, which is unpredictable to begin with and
      becomes completely unuseable if EXT_DEVT is fully used.
      It is wholely unnecessary - we already have fully functional userland
      mechanism to program devices being hotplugged which has full access to
      device identification, connection topology and filesystem information.
      Add a new struct blkio_group_conf which contains all blkcg
      configurations to blkio_group and let blkio_group, which can be
      created iff the associated device exists and is removed when the
      associated device goes away, carry all configurations.
      Note that, after this patch, all newly created blkg's will always have
      the default configuration (unlimited for throttling and blkcg's weight
      for propio).
      This patch makes blkio_policy_node meaningless but doesn't remove it.
      The next patch will.
      -v2: Updated to retry after short sleep if blkg lookup/creation failed
           due to the queue being temporarily bypassed as indicated by
           -EBUSY return.  Pointed out by Vivek.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Cc: Kay Sievers <kay.sievers@vrfy.org>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: factor out blkio_group creation · cd1604fa
      Tejun Heo authored
      Currently both blk-throttle and cfq-iosched implement their own
      blkio_group creation code in throtl_get_tg() and cfq_get_cfqg().  This
      patch factors out the common code into blkg_lookup_create(), which
      returns ERR_PTR value so that transitional failures due to queue
      bypass can be distinguished from other failures.
      * New plkio_policy_ops methods blkio_alloc_group_fn() and
        blkio_link_group_fn added.  Both are transitional and will be
        removed once the blkg management code is fully moved into
      * blkio_alloc_group_fn() allocates policy-specific blkg which is
        usually a larger data structure with blkg as the first entry and
        intiailizes it.  Note that initialization of blkg proper, including
        percpu stats, is responsibility of blk-cgroup proper.
        Note that default config (weight, bps...) initialization is done
        from this method; otherwise, we end up violating locking order
        between blkcg and q locks via blkcg_get_CONF() functions.
      * blkio_link_group_fn() is called under queue_lock and responsible for
        linking the blkg to the queue.  blkcg side is handled by blk-cgroup
      * The common blkg creation function is named blkg_lookup_create() and
        blkiocg_lookup_group() is renamed to blkg_lookup() for consistency.
        Also, throtl / cfq related functions are similarly [re]named for
      This simplifies blkcg policy implementations and enables further
      -v2: Vivek noticed that blkg_lookup_create() incorrectly tested
           blk_queue_dead() instead of blk_queue_bypass() leading a user of
           the function ending up creating a new blkg on bypassing queue.
           This is a bug introduced while relocating bypass patches before
           this one.  Fixed.
      -v3: ERR_PTR patch folded into this one.  @for_root added to
           blkg_lookup_create() to allow creating root group on a bypassed
           queue during elevator switch.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: use the usual get blkg path for root blkio_group · f51b802c
      Tejun Heo authored
      For root blkg, blk_throtl_init() was using throtl_alloc_tg()
      explicitly and cfq_init_queue() was manually initializing embedded
      cfqd->root_group, adding unnecessarily different code paths to blkg
      Make both use the usual blkio_group get functions - throtl_get_tg()
      and cfq_get_cfqg() - for the root blkio_group too.  Note that
      blk_throtl_init() callsite is pushed downwards in
      blk_alloc_queue_node() so that @q is sufficiently initialized for
      This simplifies root blkg handling noticeably for cfq and will allow
      further modularization of blkcg API.
      -v2: Vivek pointed out that using cfq_get_cfqg() won't work if
           CONFIG_CFQ_GROUP_IOSCHED is disabled.  Fix it by factoring out
           initialization of base part of cfqg into cfq_init_cfqg_base() and
           alloc/init/free explicitly if !CONFIG_CFQ_GROUP_IOSCHED.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: add blkio_policy[] array and allow one policy per policy ID · 035d10b2
      Tejun Heo authored
      Block cgroup policies are maintained in a linked list and,
      theoretically, multiple policies sharing the same policy ID are
      This patch temporarily restricts one policy per plid and adds
      blkio_policy[] array which indexes registered policy types by plid.
      Both the restriction and blkio_policy[] array are transitional and
      will be removed once API cleanup is complete.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: use q and plid instead of opaque void * for blkio_group association · ca32aefc
      Tejun Heo authored
      blkgio_group is association between a block cgroup and a queue for a
      given policy.  Using opaque void * for association makes things
      confusing and hinders factoring of common code.  Use request_queue *
      and, if necessary, policy id instead.
      This will help block cgroup API cleanup.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: update blkg get functions take blkio_cgroup as parameter · 0a5a7d0e
      Tejun Heo authored
      In both blkg get functions - throtl_get_tg() and cfq_get_cfqg(),
      instead of obtaining blkcg of %current explicitly, let the caller
      specify the blkcg to use as parameter and make both functions hold on
      to the blkcg.
      This is part of block cgroup interface cleanup and will help making
      blkcg API more modular.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: move rcu_read_lock() outside of blkio_group get functions · 2a7f1244
      Tejun Heo authored
      rcu_read_lock() in throtl_get_tb() and cfq_get_cfqg() holds onto
      @blkcg while looking up blkg.  For API cleanup, the next patch will
      make the caller responsible for determining @blkcg to look blkg from
      and let them specify it as a parameter.  Move rcu read locking out to
      the callers to prepare for the change.
      -v2: Originally this patch was described as a fix for RCU read locking
           bug around @blkg, which Vivek pointed out to be incorrect.  It
           was from misunderstanding the role of rcu locking as protecting
           @blkg not @blkcg.  Patch description updated.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: shoot down blkio_groups on elevator switch · 72e06c25
      Tejun Heo authored
      Elevator switch may involve changes to blkcg policies.  Implement
      shoot down of blkio_groups.
      Combined with the previous bypass updates, the end goal is updating
      blkcg core such that it can ensure that blkcg's being affected become
      quiescent and don't have any per-blkg data hanging around before
      commencing any policy updates.  Until queues are made aware of the
      policies that applies to them, as an interim step, all per-policy blkg
      data will be shot down.
      * blk-throtl doesn't need this change as it can't be disabled for a
        live queue; however, update it anyway as the scheduled blkg
        unification requires this behavior change.  This means that
        blk-throtl configuration will be unnecessarily lost over elevator
        switch.  This oddity will be removed after blkcg learns to associate
        individual policies with request_queues.
      * blk-throtl dosen't shoot down root_tg.  This is to ease transition.
        Unified blkg will always have persistent root group and not shooting
        down root_tg for now eases transition to that point by avoiding
        having to update td->root_tg and is safe as blk-throtl can never be
      -v2: Vivek pointed out that group list is not guaranteed to be empty
           on return from clear function if it raced cgroup removal and
           lost.  Fix it by waiting a bit and retrying.  This kludge will
           soon be removed once locking is updated such that blkg is never
           in limbo state between blkcg and request_queue locks.
           blk-throtl no longer shoots down root_tg to avoid breaking
           Also, Nest queue_lock inside blkio_list_lock not the other way
           around to avoid introduce possible deadlock via blkcg lock.
      -v3: blkcg_clear_queue() repositioned and renamed to
           blkg_destroy_all() to increase consistency with later changes.
           cfq_clear_queue() updated to check q->elevator before
           dereferencing it to avoid NULL dereference on not fully
           initialized queues (used by later change).
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      block: extend queue bypassing to cover blkcg policies · 6ecf23af
      Tejun Heo authored
      Extend queue bypassing such that dying queue is always bypassing and
      blk-throttle is drained on bypass.  With blkcg policies updated to
      test blk_queue_bypass() instead of blk_queue_dead(), this ensures that
      no bio or request is held by or going through blkcg policies on a
      bypassing queue.
      This will be used to implement blkg cleanup on elevator switches and
      policy changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      block: implement blk_queue_bypass_start/end() · d732580b
      Tejun Heo authored
      Rename and extend elv_queisce_start/end() to
      blk_queue_bypass_start/end() which are exported and supports nesting
      via @q->bypass_depth.  Also add blk_queue_bypass() to test bypass
      This will be further extended and used for blkio_group management.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      elevator: make elevator_init_fn() return 0/-errno · b2fab5ac
      Tejun Heo authored
      elevator_ops->elevator_init_fn() has a weird return value.  It returns
      a void * which the caller should assign to q->elevator->elevator_data
      and %NULL return denotes init failure.
      Update such that it returns integer 0/-errno and sets elevator_data
      directly as necessary.
      This makes the interface more conventional and eases further cleanup.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      elevator: clear auxiliary data earlier during elevator switch · 5a5bafdc
      Tejun Heo authored
      Elevator switch tries hard to keep as much as context until new
      elevator is ready so that it can revert to the original state if
      initializing the new elevator fails for some reason.  Unfortunately,
      with more auxiliary contexts to manage, this makes elevator init and
      exit paths too complex and fragile.
      This patch makes elevator_switch() unregister the current elevator and
      flush icq's before start initializing the new one.  As we still keep
      the old elevator itself, the only difference is that we lose icq's on
      rare occassions of switching failure, which isn't critical at all.
      Note that this makes explicit elevator parameter to
      elevator_init_queue() and __elv_register_queue() unnecessary as they
      always can use the current elevator.
      This patch enables block cgroup cleanups.
      -v2: blk_add_trace_msg() prints elevator name from @new_e instead of
           @e->type as the local variable no longer exists.  This caused
           build failure on CONFIG_BLK_DEV_IO_TRACE.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      cfq: don't register propio policy if !CONFIG_CFQ_GROUP_IOSCHED · b95ada55
      Tejun Heo authored
      cfq has been registering zeroed blkio_poilcy_cfq if CFQ_GROUP_IOSCHED
      is disabled.  This fortunately doesn't collide with blk-throtl as
      BLKIO_POLICY_PROP is zero but is unnecessary and risky.  Just don't
      register it if not enabled.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      blkcg: make CONFIG_BLK_CGROUP bool · 32e380ae
      Tejun Heo authored
      Block cgroup core can be built as module; however, it isn't too useful
      as blk-throttle can only be built-in and cfq-iosched is usually the
      default built-in scheduler.  Scheduled blkcg cleanup requires calling
      into blkcg from block core.  To simplify that, disallow building blkcg
      as module by making CONFIG_BLK_CGROUP bool.
      If building blkcg core as module really matters, which I doubt, we can
      revisit it after blkcg API cleanup.
      -v2: Vivek pointed out that IOSCHED_CFQ was incorrectly updated to
           depend on BLK_CGROUP.  Fixed.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      block: blk-throttle should be drained regardless of q->elevator · b855b04a
      Tejun Heo authored
      Currently, blk_cleanup_queue() doesn't call elv_drain_elevator() if
      q->elevator doesn't exist; however, bio based drivers don't have
      elevator initialized but can still use blk-throttle.  This patch moves
      q->elevator test inside blk_drain_queue() such that only
      elv_drain_elevator() is skipped if !q->elevator.
      -v2: loop can have registered queue which has NULL request_fn.  Make
           sure we don't call into __blk_run_queue() in such cases.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reported-by: default avatarVivek Goyal <vgoyal@redhat.com>
      Fold in bug fix from Vivek.
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
  2. 03 Mar, 2012 1 commit
  3. 02 Mar, 2012 6 commits
    • Alan Stern's avatar
      Block: use a freezable workqueue for disk-event polling · 62d3c543
      Alan Stern authored
      This patch (as1519) fixes a bug in the block layer's disk-events
      polling.  The polling is done by a work routine queued on the
      system_nrt_wq workqueue.  Since that workqueue isn't freezable, the
      polling continues even in the middle of a system sleep transition.
      Obviously, polling a suspended drive for media changes and such isn't
      a good thing to do; in the case of USB mass-storage devices it can
      lead to real problems requiring device resets and even re-enumeration.
      The patch fixes things by creating a new system-wide, non-reentrant,
      freezable workqueue and using it for disk-events polling.
      Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
      CC: <stable@kernel.org>
      Acked-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Danny Kukawka's avatar
      drivers/block/DAC960: fix -Wuninitialized warning · cecd353a
      Danny Kukawka authored
      Set CommandMailbox with memset before use it. Fix for:
      drivers/block/DAC960.c: In function ‘DAC960_V1_EnableMemoryMailboxInterface’:
      arch/x86/include/asm/io.h:61:1: warning: ‘CommandMailbox.Bytes[12]’
       may be used uninitialized in this function [-Wuninitialized]
      drivers/block/DAC960.c:1175:30: note: ‘CommandMailbox.Bytes[12]’
       was declared here
      Signed-off-by: default avatarDanny Kukawka <danny.kukawka@bisect.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Danny Kukawka's avatar
      drivers/block/DAC960: fix DAC960_V2_IOCTL_Opcode_T -Wenum-compare warning · bca505f1
      Danny Kukawka authored
      Fixed compiler warning:
      comparison between ‘DAC960_V2_IOCTL_Opcode_T’ and ‘enum <anonymous>’
      Renamed enum, added a new enum for SCSI_10.CommandOpcode in
      Signed-off-by: default avatarDanny Kukawka <danny.kukawka@bisect.de>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Stanislaw Gruszka's avatar
      block: fix __blkdev_get and add_disk race condition · 9f53d2fe
      Stanislaw Gruszka authored
      The following situation might occur:
      __blkdev_get:			add_disk:
      	disk->ev == NULL
      	disk->ev != NULL
      Then we unblock events, when they are suppose to be blocked. This can
      trigger events related block/genhd.c warnings, but also can crash in
      sd_check_events() or other places.
      I'm able to reproduce crashes with the following scripts (with
      connected usb dongle as sdb disk).
      function stop_me()
      	for i in `jobs -p` ; do kill $i 2> /dev/null ; done
      trap stop_me SIGHUP SIGINT SIGTERM
      for ((i = 0; i < 10; i++)) ; do
      	while true; do fdisk -l $DEV  2>&1 > /dev/null ; done &
      while true ; do
      echo 1 > $ENABLE
      sleep 1
      echo 0 > $ENABLE
      I use the script to verify patch fixing oops in sd_revalidate_disk
      Without Jun'ichi Nomura patch titled "Fix NULL pointer dereference in
      sd_revalidate_disk" or this one, script easily crash kernel within
      a few seconds. With both patches applied I do not observe crash.
      Unfortunately after some time (dozen of minutes), script will hung in:
      [ 1563.906432]  [<c08354f5>] schedule_timeout_uninterruptible+0x15/0x20
      [ 1563.906437]  [<c04532d5>] msleep+0x15/0x20
      [ 1563.906443]  [<c05d60b2>] blk_drain_queue+0x32/0xd0
      [ 1563.906447]  [<c05d6e00>] blk_cleanup_queue+0xd0/0x170
      [ 1563.906454]  [<c06d278f>] scsi_free_queue+0x3f/0x60
      [ 1563.906459]  [<c06d7e6e>] __scsi_remove_device+0x6e/0xb0
      [ 1563.906463]  [<c06d4aff>] scsi_forget_host+0x4f/0x60
      [ 1563.906468]  [<c06cd84a>] scsi_remove_host+0x5a/0xf0
      [ 1563.906482]  [<f7f030fb>] quiesce_and_remove_host+0x5b/0xa0 [usb_storage]
      [ 1563.906490]  [<f7f03203>] usb_stor_disconnect+0x13/0x20 [usb_storage]
      Anyway I think this patch is some step forward.
      As drawback, I do not teardown on sysfs file create error, because I do
      not know how to nullify disk->ev (since it can be used). However add_disk
      error handling practically does not exist too, and things will work
      without this sysfs file, except events will not be exported to user
      Signed-off-by: default avatarStanislaw Gruszka <sgruszka@redhat.com>
      Acked-by: default avatarTejun Heo <tj@kernel.org>
      Cc: stable@kernel.org
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Muthukumar R's avatar
      block: Fix setting bio flags in drivers (sd_dif/floppy) · 12ebffd1
      Muthukumar R authored
      Fix setting bio flags in drivers (sd_dif/floppy).
      Signed-off-by: default avatarMuthukumar R <muthur@gmail.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Jun'ichi Nomura's avatar
      block: Fix NULL pointer dereference in sd_revalidate_disk · fe316bf2
      Jun'ichi Nomura authored
      Since 2.6.39 (1196f8b8), when a driver returns -ENOMEDIUM for open(),
      __blkdev_get() calls rescan_partitions() to remove
      in-kernel partition structures and raise KOBJ_CHANGE uevent.
      However it ends up calling driver's revalidate_disk without open
      and could cause oops.
      In the case of SCSI:
        process A                  process B
              returns -ENOMEDIUM
                                     <scsi_device torn down>
      Oopses are reported here:
      This patch separates the partition invalidation from rescan_partitions()
      and use it for -ENOMEDIUM case.
      Reported-by: default avatarHuajun Li <huajun.li.lee@gmail.com>
      Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
      Acked-by: default avatarTejun Heo <tj@kernel.org>
      Cc: stable@kernel.org
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
  4. 15 Feb, 2012 3 commits
    • Tejun Heo's avatar
      block: exit_io_context() should call elevator_exit_icq_fn() · 621032ad
      Tejun Heo authored
      While updating locking, b2efa052 "block, cfq: unlink
      cfq_io_context's immediately" moved elevator_exit_icq_fn() invocation
      from exit_io_context() to the final ioc put.  While this doesn't cause
      catastrophic failure, it effectively removes task exit notification to
      elevator and cause noticeable IO performance degradation with CFQ.
      On task exit, CFQ used to immediately expire the slice if it was being
      used by the exiting task as no more IO would be issued by the task;
      however, after b2efa052
      , the notification is lost and disk could sit
      idle needlessly, leading to noticeable IO performance degradation for
      certain workloads.
      This patch renames ioc_exit_icq() to ioc_destroy_icq(), separates
      elevator_exit_icq_fn() invocation into ioc_exit_icq() and invokes it
      from exit_io_context().  ICQ_EXITED flag is added to avoid invoking
      the callback more than once for the same icq.
      Walking icq_list from ioc side and invoking elevator callback requires
      reverse double locking.  This may be better implemented using RCU;
      unfortunately, using RCU isn't trivial.  e.g. RCU protection would
      need to cover request_queue and queue_lock switch on cleanup makes
      grabbing queue_lock from RCU unsafe.  Reverse double locking should
      do, at least for now.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reported-and-bisected-by: default avatarShaohua Li <shli@kernel.org>
      LKML-Reference: <CANejiEVzs=pUhQSTvUppkDcc2TNZyfohBRLygW5zFmXyk5A-xQ@mail.gmail.com>
      Tested-by: default avatarShaohua Li <shaohua.li@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      block: simplify ioc_release_fn() · 2274b029
      Tejun Heo authored
      Reverse double lock dancing in ioc_release_fn() can be simplified by
      just using trylock on the queue_lock and back out from ioc lock on
      trylock failure.  Simplify it.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Tested-by: default avatarShaohua Li <shaohua.li@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    • Tejun Heo's avatar
      block: replace icq->changed with icq->flags · d705ae6b
      Tejun Heo authored
      icq->changed was used for ICQ_*_CHANGED bits.  Rename it to flags and
      access it under ioc->lock instead of using atomic bitops.
      ioc_get_changed() is added so that the changed part can be fetched and
      cleared as before.
      icq->flags will be used to carry other flags.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Tested-by: default avatarShaohua Li <shaohua.li@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
  5. 14 Feb, 2012 2 commits