1. 02 Jun, 2015 23 commits
    • Tejun Heo's avatar
      writeback: make backing_dev_info host cgroup-specific bdi_writebacks · 52ebea74
      Tejun Heo authored
      
      
      For the planned cgroup writeback support, on each bdi
      (backing_dev_info), each memcg will be served by a separate wb
      (bdi_writeback).  This patch updates bdi so that a bdi can host
      multiple wbs (bdi_writebacks).
      
      On the default hierarchy, blkcg implicitly enables memcg.  This allows
      using memcg's page ownership for attributing writeback IOs, and every
      memcg - blkcg combination can be served by its own wb by assigning a
      dedicated wb to each memcg.  This means that there may be multiple
      wb's of a bdi mapped to the same blkcg.  As congested state is per
      blkcg - bdi combination, those wb's should share the same congested
      state.  This is achieved by tracking congested state via
      bdi_writeback_congested structs which are keyed by blkcg.
      
      bdi->wb remains unchanged and will keep serving the root cgroup.
      cgwb's (cgroup wb's) for non-root cgroups are created on-demand or
      looked up while dirtying an inode according to the memcg of the page
      being dirtied or current task.  Each cgwb is indexed on bdi->cgwb_tree
      by its memcg id.  Once an inode is associated with its wb, it can be
      retrieved using inode_to_wb().
      
      Currently, none of the filesystems has FS_CGROUP_WRITEBACK and all
      pages will keep being associated with bdi->wb.
      
      v3: inode_attach_wb() in account_page_dirtied() moved inside
          mapping_cap_account_dirty() block where it's known to be !NULL.
          Also, an unnecessary NULL check before kfree() removed.  Both
          detected by the kbuild bot.
      
      v2: Updated so that wb association is per inode and wb is per memcg
          rather than blkcg.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: kbuild test robot <fengguang.wu@intel.com>
      Cc: Dan Carpenter <dan.carpenter@oracle.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Jan Kara <jack@suse.cz>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      52ebea74
    • Tejun Heo's avatar
      writeback: add {CONFIG|BDI_CAP|FS}_CGROUP_WRITEBACK · 89e9b9e0
      Tejun Heo authored
      
      
      cgroup writeback requires support from both bdi and filesystem sides.
      Add BDI_CAP_CGROUP_WRITEBACK and FS_CGROUP_WRITEBACK to indicate
      support and enable BDI_CAP_CGROUP_WRITEBACK on block based bdi's by
      default.  Also, define CONFIG_CGROUP_WRITEBACK which is enabled if
      both MEMCG and BLK_CGROUP are enabled.
      
      inode_cgwb_enabled() which determines whether a given inode's both bdi
      and fs support cgroup writeback is added.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Jan Kara <jack@suse.cz>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      89e9b9e0
    • Tejun Heo's avatar
      bdi: separate out congested state into a separate struct · 4aa9c692
      Tejun Heo authored
      
      
      Currently, a wb's (bdi_writeback) congestion state is carried in its
      ->state field; however, cgroup writeback support will require multiple
      wb's sharing the same congestion state.  This patch separates out
      congestion state into its own struct - struct bdi_writeback_congested.
      A new field wb field, wb_congested, points to its associated congested
      struct.  The default wb, bdi->wb, always points to bdi->wb_congested.
      
      While this patch adds a layer of indirection, it doesn't introduce any
      behavior changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      4aa9c692
    • Tejun Heo's avatar
      writeback: add @gfp to wb_init() · 8395cd9f
      Tejun Heo authored
      
      
      wb_init() currently always uses GFP_KERNEL but the planned cgroup
      writeback support needs using other allocation masks.  Add @gfp to
      wb_init().
      
      This patch doesn't introduce any behavior changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@kernel.dk>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      8395cd9f
    • Tejun Heo's avatar
      bdi: make inode_to_bdi() inline · a212b105
      Tejun Heo authored
      
      
      Now that bdi definitions are moved to backing-dev-defs.h,
      backing-dev.h can include blkdev.h and inline inode_to_bdi() without
      worrying about introducing circular include dependency.  The function
      gets called from hot paths and fairly trivial.
      
      This patch makes inode_to_bdi() and sb_is_blkdev_sb() that the
      function calls inline.  blockdev_superblock and noop_backing_dev_info
      are EXPORT_GPL'd to allow the inline functions to be used from
      modules.
      
      While at it, make sb_is_blkdev_sb() return bool instead of int.
      
      v2: Fixed typo in description as suggested by Jan.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJens Axboe <axboe@kernel.dk>
      Cc: Christoph Hellwig <hch@infradead.org>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      a212b105
    • Tejun Heo's avatar
      writeback: separate out include/linux/backing-dev-defs.h · 66114cad
      Tejun Heo authored
      
      
      With the planned cgroup writeback support, backing-dev related
      declarations will be more widely used across block and cgroup;
      unfortunately, including backing-dev.h from include/linux/blkdev.h
      makes cyclic include dependency quite likely.
      
      This patch separates out backing-dev-defs.h which only has the
      essential definitions and updates blkdev.h to include it.  c files
      which need access to more backing-dev details now include
      backing-dev.h directly.  This takes backing-dev.h off the common
      include dependency chain making it a lot easier to use it across block
      and cgroup.
      
      v2: fs/fat build failure fixed.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@kernel.dk>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      66114cad
    • Tejun Heo's avatar
      writeback: reorganize mm/backing-dev.c · 46100071
      Tejun Heo authored
      
      
      Move wb_shutdown(), bdi_register(), bdi_register_dev(),
      bdi_prune_sb(), bdi_remove_from_list() and bdi_unregister() so that
      init / exit functions are grouped together.  This will make updating
      init / exit paths for cgroup writeback support easier.
      
      This is pure source file reorganization.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      46100071
    • Tejun Heo's avatar
      writeback: move backing_dev_info->wb_lock and ->worklist into bdi_writeback · f0054bb1
      Tejun Heo authored
      
      
      Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
      and the role of the separation is unclear.  For cgroup support for
      writeback IOs, a bdi will be updated to host multiple wb's where each
      wb serves writeback IOs of a different cgroup on the bdi.  To achieve
      that, a wb should carry all states necessary for servicing writeback
      IOs for a cgroup independently.
      
      This patch moves bdi->wb_lock and ->worklist into wb.
      
      * The lock protects bdi->worklist and bdi->wb.dwork scheduling.  While
        moving, rename it to wb->work_lock as wb->wb_lock is confusing.
        Also, move wb->dwork downwards so that it's colocated with the new
        ->work_lock and ->work_list fields.
      
      * bdi_writeback_workfn()		-> wb_workfn()
        bdi_wakeup_thread_delayed(bdi)	-> wb_wakeup_delayed(wb)
        bdi_wakeup_thread(bdi)		-> wb_wakeup(wb)
        bdi_queue_work(bdi, ...)		-> wb_queue_work(wb, ...)
        __bdi_start_writeback(bdi, ...)	-> __wb_start_writeback(wb, ...)
        get_next_work_item(bdi)		-> get_next_work_item(wb)
      
      * bdi_wb_shutdown() is renamed to wb_shutdown() and now takes @wb.
        The function contained parts which belong to the containing bdi
        rather than the wb itself - testing cap_writeback_dirty and
        bdi_remove_from_list() invocation.  Those are moved to
        bdi_unregister().
      
      * bdi_wb_{init|exit}() are renamed to wb_{init|exit}().
        Initializations of the moved bdi->wb_lock and ->work_list are
        relocated from bdi_init() to wb_init().
      
      * As there's still only one bdi_writeback per backing_dev_info, all
        uses of bdi->state are mechanically replaced with bdi->wb.state
        introducing no behavior changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      f0054bb1
    • Tejun Heo's avatar
      writeback: s/bdi/wb/ in mm/page-writeback.c · de1fff37
      Tejun Heo authored
      
      
      Writeback operations will now be per wb (bdi_writeback) instead of
      bdi.  Replace the relevant bdi references in symbol names and comments
      with wb.  This patch is purely cosmetic and doesn't make any
      functional changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      de1fff37
    • Tejun Heo's avatar
      writeback: move bandwidth related fields from backing_dev_info into bdi_writeback · a88a341a
      Tejun Heo authored
      
      
      Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
      and the role of the separation is unclear.  For cgroup support for
      writeback IOs, a bdi will be updated to host multiple wb's where each
      wb serves writeback IOs of a different cgroup on the bdi.  To achieve
      that, a wb should carry all states necessary for servicing writeback
      IOs for a cgroup independently.
      
      This patch moves bandwidth related fields from backing_dev_info into
      bdi_writeback.
      
      * The moved fields are: bw_time_stamp, dirtied_stamp, written_stamp,
        write_bandwidth, avg_write_bandwidth, dirty_ratelimit,
        balanced_dirty_ratelimit, completions and dirty_exceeded.
      
      * writeback_chunk_size() and over_bground_thresh() now take @wb
        instead of @bdi.
      
      * bdi_writeout_fraction(bdi, ...)	-> wb_writeout_fraction(wb, ...)
        bdi_dirty_limit(bdi, ...)		-> wb_dirty_limit(wb, ...)
        bdi_position_ration(bdi, ...)		-> wb_position_ratio(wb, ...)
        bdi_update_writebandwidth(bdi, ...)	-> wb_update_write_bandwidth(wb, ...)
        [__]bdi_update_bandwidth(bdi, ...)	-> [__]wb_update_bandwidth(wb, ...)
        bdi_{max|min}_pause(bdi, ...)		-> wb_{max|min}_pause(wb, ...)
        bdi_dirty_limits(bdi, ...)		-> wb_dirty_limits(wb, ...)
      
      * Init/exits of the relocated fields are moved to bdi_wb_init/exit()
        respectively.  Note that explicit zeroing is dropped in the process
        as wb's are cleared in entirety anyway.
      
      * As there's still only one bdi_writeback per backing_dev_info, all
        uses of bdi->stat[] are mechanically replaced with bdi->wb.stat[]
        introducing no behavior changes.
      
      v2: Typo in description fixed as suggested by Jan.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Cc: Jaegeuk Kim <jaegeuk@kernel.org>
      Cc: Steven Whitehouse <swhiteho@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      a88a341a
    • Tejun Heo's avatar
      writeback: move backing_dev_info->bdi_stat[] into bdi_writeback · 93f78d88
      Tejun Heo authored
      
      
      Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
      and the role of the separation is unclear.  For cgroup support for
      writeback IOs, a bdi will be updated to host multiple wb's where each
      wb serves writeback IOs of a different cgroup on the bdi.  To achieve
      that, a wb should carry all states necessary for servicing writeback
      IOs for a cgroup independently.
      
      This patch moves bdi->bdi_stat[] into wb.
      
      * enum bdi_stat_item is renamed to wb_stat_item and the prefix of all
        enums is changed from BDI_ to WB_.
      
      * BDI_STAT_BATCH() -> WB_STAT_BATCH()
      
      * [__]{add|inc|dec|sum}_wb_stat(bdi, ...) -> [__]{add|inc}_wb_stat(wb, ...)
      
      * bdi_stat[_error]() -> wb_stat[_error]()
      
      * bdi_writeout_inc() -> wb_writeout_inc()
      
      * stat init is moved to bdi_wb_init() and bdi_wb_exit() is added and
        frees stat.
      
      * As there's still only one bdi_writeback per backing_dev_info, all
        uses of bdi->stat[] are mechanically replaced with bdi->wb.stat[]
        introducing no behavior changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Cc: Miklos Szeredi <miklos@szeredi.hu>
      Cc: Trond Myklebust <trond.myklebust@primarydata.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      93f78d88
    • Tejun Heo's avatar
      writeback: move backing_dev_info->state into bdi_writeback · 4452226e
      Tejun Heo authored
      
      
      Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
      and the role of the separation is unclear.  For cgroup support for
      writeback IOs, a bdi will be updated to host multiple wb's where each
      wb serves writeback IOs of a different cgroup on the bdi.  To achieve
      that, a wb should carry all states necessary for servicing writeback
      IOs for a cgroup independently.
      
      This patch moves bdi->state into wb.
      
      * enum bdi_state is renamed to wb_state and the prefix of all enums is
        changed from BDI_ to WB_.
      
      * Explicit zeroing of bdi->state is removed without adding zeoring of
        wb->state as the whole data structure is zeroed on init anyway.
      
      * As there's still only one bdi_writeback per backing_dev_info, all
        uses of bdi->state are mechanically replaced with bdi->wb.state
        introducing no behavior changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Wu Fengguang <fengguang.wu@intel.com>
      Cc: drbd-dev@lists.linbit.com
      Cc: Neil Brown <neilb@suse.de>
      Cc: Alasdair Kergon <agk@redhat.com>
      Cc: Mike Snitzer <snitzer@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      4452226e
    • Tejun Heo's avatar
      memcg: implement mem_cgroup_css_from_page() · ad7fa852
      Tejun Heo authored
      
      
      Implement mem_cgroup_css_from_page() which returns the
      cgroup_subsys_state of the memcg associated with a given page on the
      default hierarchy.  This will be used by cgroup writeback support.
      
      This function assumes that page->mem_cgroup association doesn't change
      until the page is released, which is true on the default hierarchy as
      long as replace_page_cache_page() is not used.  As the only user of
      replace_page_cache_page() is FUSE which won't support cgroup writeback
      for the time being, this works for now, and replace_page_cache_page()
      will soon be updated so that the invariant actually holds.
      
      Note that the RCU protected page->mem_cgroup access is consistent with
      other usages across memcg but ultimately incorrect.  These unlocked
      accesses are missing required barriers.  page->mem_cgroup should be
      made an RCU pointer and updated and accessed using RCU operations.
      
      v4: Instead of triggering WARN, return the root css on the traditional
          hierarchies.  This makes the function a lot easier to deal with
          especially as there's no light way to synchronize against
          hierarchy rebinding.
      
      v3: s/mem_cgroup_migrate()/mem_cgroup_css_from_page()/
      
      v2: Trigger WARN if the function is used on the traditional
          hierarchies and add comment about the assumed invariant.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      Cc: Michal Hocko <mhocko@suse.cz>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      ad7fa852
    • Tejun Heo's avatar
      blkcg: implement bio_associate_blkcg() · 1d933cf0
      Tejun Heo authored
      
      
      Currently, a bio can only be associated with the io_context and blkcg
      of %current using bio_associate_current().  This is too restrictive
      for cgroup writeback support.  Implement bio_associate_blkcg() which
      associates a bio with the specified blkcg.
      
      bio_associate_blkcg() leaves the io_context unassociated.
      bio_associate_current() is updated so that it considers a bio as
      already associated if it has a blkcg_css, instead of an io_context,
      associated with it.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      1d933cf0
    • Tejun Heo's avatar
      blkcg: implement task_get_blkcg_css() · fd383c2d
      Tejun Heo authored
      
      
      Implement a wrapper around task_get_css() to acquire the blkcg css for
      a given task.  The wrapper is necessary for cgroup writeback support
      as there will be places outside blkcg proper trying to acquire
      blkcg_css and blkio_cgrp_id will be undefined when !CONFIG_BLK_CGROUP.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      fd383c2d
    • Tejun Heo's avatar
      cgroup, block: implement task_get_css() and use it in bio_associate_current() · ec438699
      Tejun Heo authored
      
      
      bio_associate_current() currently open codes task_css() and
      css_tryget_online() to find and pin $current's blkcg css.  Abstract it
      into task_get_css() which is implemented from cgroup side.  As a task
      is always associated with an online css for every subsystem except
      while the css_set update is propagating, task_get_css() retries till
      css_tryget_online() succeeds.
      
      This is a cleanup and shouldn't lead to noticeable behavior changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Li Zefan <lizefan@huawei.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      ec438699
    • Tejun Heo's avatar
      blkcg: add blkcg_root_css · 496d5e75
      Tejun Heo authored
      
      
      Add global constant blkcg_root_css which points to &blkcg_root.css.
      This will be used by cgroup writeback support.  If blkcg is disabled,
      it's defined as ERR_PTR(-EINVAL).
      
      v2: The declarations moved to include/linux/blk-cgroup.h as suggested
          by Vivek.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Cc: Jens Axboe <axboe@kernel.dk>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      496d5e75
    • Tejun Heo's avatar
      memcg: add mem_cgroup_root_css · 56161634
      Tejun Heo authored
      
      
      Add global mem_cgroup_root_css which points to the root memcg css.
      This will be used by cgroup writeback support.  If memcg is disabled,
      it's defined as ERR_PTR(-EINVAL).
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Johannes Weiner <hannes@cmpxchg.org>
      aCc: Michal Hocko <mhocko@suse.cz>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      56161634
    • Tejun Heo's avatar
      blkcg: always create the blkcg_gq for the root blkcg · ec13b1d6
      Tejun Heo authored
      
      
      Currently, blkcg does a minor optimization where the root blkcg is
      created when the first blkcg policy is activated on a queue and
      destroyed on the deactivation of the last.  On systems where blkcg is
      configured but not used, this saves one blkcg_gq struct per queue.  On
      systems where blkcg is actually used, there's no difference.  The only
      case where this can lead to any meaninful, albeit still minute, save
      in memory consumption is when all blkcg policies are deactivated after
      being widely used in the system, which is a hihgly unlikely scenario.
      
      The conditional existence of root blkcg_gq has already created several
      bugs in blkcg and became an issue once again for the new per-cgroup
      wb_congested mechanism for cgroup writeback support leading to a NULL
      dereference when no blkcg policy is active.  This is really not worth
      bothering with.  This patch makes blkcg always allocate and link the
      root blkcg_gq and release it only on queue destruction.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      ec13b1d6
    • Tejun Heo's avatar
      update !CONFIG_BLK_CGROUP dummies in include/linux/blk-cgroup.h · efa7d1c7
      Tejun Heo authored
      
      
      The header file will be used more widely with the pending cgroup
      writeback support and the current set of dummy declarations aren't
      enough to handle different config combinations.  Update as follows.
      
      * Drop the struct cgroup declaration.  None of the dummy defs need it.
      
      * Define blkcg as an empty struct instead of just declaring it.
      
      * Wrap dummy function defs in CONFIG_BLOCK.  Some functions use block
        data types and none of them are to be used w/o block enabled.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      efa7d1c7
    • Tejun Heo's avatar
      blkcg: move block/blk-cgroup.h to include/linux/blk-cgroup.h · eea8f41c
      Tejun Heo authored
      
      
      cgroup aware writeback support will require exposing some of blkcg
      details.  In preprataion, move block/blk-cgroup.h to
      include/linux/blk-cgroup.h.  This patch is pure file move.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      eea8f41c
    • Greg Thelen's avatar
      memcg: add per cgroup dirty page accounting · c4843a75
      Greg Thelen authored
      When modifying PG_Dirty on cached file pages, update the new
      MEM_CGROUP_STAT_DIRTY counter.  This is done in the same places where
      global NR_FILE_DIRTY is managed.  The new memcg stat is visible in the
      per memcg memory.stat cgroupfs file.  The most recent past attempt at
      this was http://thread.gmane.org/gmane.linux.kernel.cgroups/8632
      
      The new accounting supports future efforts to add per cgroup dirty
      page throttling and writeback.  It also helps an administrator break
      down a container's memory usage and provides evidence to understand
      memcg oom kills (the new dirty count is included in memcg oom kill
      messages).
      
      The ability to move page accounting between memcg
      (memory.move_charge_at_immigrate) makes this accounting more
      complicated than the global counter.  The existing
      mem_cgroup_{begin,end}_page_stat() lock is used to serialize move
      accounting with stat updates.
      Typical update operation:
      	memcg = mem_cgroup_begin_page_stat(page)
      	if (TestSetPageDirty()) {
      		[...]
      		mem_cgroup_update_page_stat(memcg)
      	}
      	mem_cgroup_end_page_stat(memcg)
      
      Summary of mem_cgroup_end_page_stat() overhead:
      - Without CONFIG_MEMCG it's a no-op
      - With CONFIG_MEMCG and no inter memcg task movement, it's just
        rcu_read_lock()
      - With CONFIG_MEMCG and inter memcg  task movement, it's
        rcu_read_lock() + spin_lock_irqsave()
      
      A memcg parameter is added to several routines because their callers
      now grab mem_cgroup_begin_page_stat() which returns the memcg later
      needed by for mem_cgroup_update_page_stat().
      
      Because mem_cgroup_begin_page_stat() may disable interrupts, some
      adjustments are needed:
      - move __mark_inode_dirty() from __set_page_dirty() to its caller.
        __mark_inode_dirty() locking does not want interrupts disabled.
      - use spin_lock_irqsave(tree_lock) rather than spin_lock_irq() in
        __delete_from_page_cache(), replace_page_cache_page(),
        invalidate_complete_page2(), and __remove_mapping().
      
         text    data     bss      dec    hex filename
      8925147 1774832 1785856 12485835 be84cb vmlinux-!CONFIG_MEMCG-before
      8925339 1774832 1785856 12486027 be858b vmlinux-!CONFIG_MEMCG-after
                                  +192 text bytes
      8965977 1784992 1785856 12536825 bf4bf9 vmlinux-CONFIG_MEMCG-before
      8966750 1784992 1785856 12537598 bf4efe vmlinux-CONFIG_MEMCG-after
                                  +773 text bytes
      
      Performance tests run on v4.0-rc1-36-g4f671fe2
      
      .  Lower is better for
      all metrics, they're all wall clock or cycle counts.  The read and write
      fault benchmarks just measure fault time, they do not include I/O time.
      
      * CONFIG_MEMCG not set:
                                  baseline                              patched
        kbuild                 1m25.030000(+-0.088% 3 samples)       1m25.426667(+-0.120% 3 samples)
        dd write 100 MiB          0.859211561 +-15.10%                  0.874162885 +-15.03%
        dd write 200 MiB          1.670653105 +-17.87%                  1.669384764 +-11.99%
        dd write 1000 MiB         8.434691190 +-14.15%                  8.474733215 +-14.77%
        read fault cycles       254.0(+-0.000% 10 samples)            253.0(+-0.000% 10 samples)
        write fault cycles     2021.2(+-3.070% 10 samples)           1984.5(+-1.036% 10 samples)
      
      * CONFIG_MEMCG=y root_memcg:
                                  baseline                              patched
        kbuild                 1m25.716667(+-0.105% 3 samples)       1m25.686667(+-0.153% 3 samples)
        dd write 100 MiB          0.855650830 +-14.90%                  0.887557919 +-14.90%
        dd write 200 MiB          1.688322953 +-12.72%                  1.667682724 +-13.33%
        dd write 1000 MiB         8.418601605 +-14.30%                  8.673532299 +-15.00%
        read fault cycles       266.0(+-0.000% 10 samples)            266.0(+-0.000% 10 samples)
        write fault cycles     2051.7(+-1.349% 10 samples)           2049.6(+-1.686% 10 samples)
      
      * CONFIG_MEMCG=y non-root_memcg:
                                  baseline                              patched
        kbuild                 1m26.120000(+-0.273% 3 samples)       1m25.763333(+-0.127% 3 samples)
        dd write 100 MiB          0.861723964 +-15.25%                  0.818129350 +-14.82%
        dd write 200 MiB          1.669887569 +-13.30%                  1.698645885 +-13.27%
        dd write 1000 MiB         8.383191730 +-14.65%                  8.351742280 +-14.52%
        read fault cycles       265.7(+-0.172% 10 samples)            267.0(+-0.000% 10 samples)
        write fault cycles     2070.6(+-1.512% 10 samples)           2084.4(+-2.148% 10 samples)
      
      As expected anon page faults are not affected by this patch.
      
      tj: Updated to apply on top of the recent cancel_dirty_page() changes.
      Signed-off-by: default avatarSha Zhengju <handai.szj@gmail.com>
      Signed-off-by: default avatarGreg Thelen <gthelen@google.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      c4843a75
    • Tejun Heo's avatar
      page_writeback: revive cancel_dirty_page() in a restricted form · 11f81bec
      Tejun Heo authored
      cancel_dirty_page() had some issues and b9ea2515
      
       ("page_writeback:
      clean up mess around cancel_dirty_page()") replaced it with
      account_page_cleaned() which makes the caller responsible for clearing
      the dirty bit; unfortunately, the planned changes for cgroup writeback
      support requires synchronization between dirty bit manipulation and
      stat updates.  While we can open-code such synchronization in each
      account_page_cleaned() callsite, that's gonna be unnecessarily awkward
      and verbose.
      
      This patch revives cancel_dirty_page() but in a more restricted form.
      All it does is TestClearPageDirty() followed by account_page_cleaned()
      invocation if the page was dirty.  This helper covers all
      account_page_cleaned() usages except for __delete_from_page_cache()
      which is a special case anyway and left alone.  As this leaves no
      module user for account_page_cleaned(), EXPORT_SYMBOL() is dropped
      from it.
      
      This patch just revives cancel_dirty_page() as a trivial wrapper to
      replace equivalent usages and doesn't introduce any functional
      changes.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      11f81bec
  2. 01 Jun, 2015 1 commit
    • Keith Busch's avatar
      blk-mq: Shared tag enhancements · f26cdc85
      Keith Busch authored
      
      
      Storage controllers may expose multiple block devices that share hardware
      resources managed by blk-mq. This patch enhances the shared tags so a
      low-level driver can access the shared resources not tied to the unshared
      h/w contexts. This way the LLD can dynamically add and delete disks and
      request queues without having to track all the request_queue hctx's to
      iterate outstanding tags.
      Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      f26cdc85
  3. 29 May, 2015 2 commits
  4. 26 May, 2015 1 commit
  5. 22 May, 2015 2 commits
    • Christoph Hellwig's avatar
      block, dm: don't copy bios for request clones · 5f1b670d
      Christoph Hellwig authored
      
      
      Currently dm-multipath has to clone the bios for every request sent
      to the lower devices, which wastes cpu cycles and ties down memory.
      
      This patch instead adds a new REQ_CLONE flag that instructs req_bio_endio
      to not complete bios attached to a request, which we set on clone
      requests similar to bios in a flush sequence.  With this change I/O
      errors on a path failure only get propagated to dm-multipath, which
      can then either resubmit the I/O or complete the bios on the original
      request.
      
      I've done some basic testing of this on a Linux target with ALUA support,
      and it survives path failures during I/O nicely.
      Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      5f1b670d
    • Mike Snitzer's avatar
      block: remove management of bi_remaining when restoring original bi_end_io · 326e1dbb
      Mike Snitzer authored
      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: default avatarChristoph Hellwig <hch@lst.de>
      Reviewed-by: default avatarJan Kara <jack@suse.cz>
      Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      326e1dbb
  6. 20 May, 2015 2 commits
    • Ming Lei's avatar
      block: replace trylock with mutex_lock in blkdev_reread_part() · b04a5636
      Ming Lei authored
      
      
      The only possible problem of using mutex_lock() instead of trylock
      is about deadlock.
      
      If there aren't any locks held before calling blkdev_reread_part(),
      deadlock can't be caused by this conversion.
      
      If there are locks held before calling blkdev_reread_part(),
      and if these locks arn't required in open, close handler and I/O
      path, deadlock shouldn't be caused too.
      
      Both user space's ioctl(BLKRRPART) and md_setup_drive() from
      init/do_mounts_md.c belongs to the 1st case, so the conversion is safe
      for the two cases.
      
      For loop, the previous patches in this pathset has fixed the ABBA lock
      dependency, so the conversion is OK.
      
      For nbd, tx_lock is held when calling the function:
      
      	- both open and release won't hold the lock
      	- when blkdev_reread_part() is run, I/O thread has been stopped
      	already, so tx_lock won't be acquired in I/O path at that time.
      	- so the conversion won't cause deadlock for nbd
      
      For dasd, both dasd_open(), dasd_release() and request function don't
      acquire any mutex/semphone, so the conversion should be safe.
      Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
      Tested-by: default avatarJarod Wilson <jarod@redhat.com>
      Acked-by: default avatarJarod Wilson <jarod@redhat.com>
      Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      b04a5636
    • Jarod Wilson's avatar
      block: export blkdev_reread_part() and __blkdev_reread_part() · be324177
      Jarod Wilson authored
      
      
      This patch exports blkdev_reread_part() for block drivers, also
      introduce __blkdev_reread_part().
      
      For some drivers, such as loop, reread of partitions can be run
      from the release path, and bd_mutex may already be held prior to
      calling ioctl_by_bdev(bdev, BLKRRPART, 0), so introduce
      __blkdev_reread_part for use in such cases.
      
      CC: Christoph Hellwig <hch@lst.de>
      CC: Jens Axboe <axboe@kernel.dk>
      CC: Tejun Heo <tj@kernel.org>
      CC: Alexander Viro <viro@zeniv.linux.org.uk>
      CC: Markus Pargmann <mpa@pengutronix.de>
      CC: Stefan Weinhuber <wein@de.ibm.com>
      CC: Stefan Haberland <stefan.haberland@de.ibm.com>
      CC: Sebastian Ott <sebott@linux.vnet.ibm.com>
      CC: Fabian Frederick <fabf@skynet.be>
      CC: Ming Lei <ming.lei@canonical.com>
      CC: David Herrmann <dh.herrmann@gmail.com>
      CC: Andrew Morton <akpm@linux-foundation.org>
      CC: Peter Zijlstra <peterz@infradead.org>
      CC: nbd-general@lists.sourceforge.net
      CC: linux-s390@vger.kernel.org
      Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarJarod Wilson <jarod@redhat.com>
      Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      be324177
  7. 19 May, 2015 5 commits
  8. 08 May, 2015 4 commits
    • Shaohua Li's avatar
      blk-mq: make plug work for mutiple disks and queues · 5b3f341f
      Shaohua Li authored
      
      
      Last patch makes plug work for multiple queue case. However it only
      works for single disk case, because it assumes only one request in the
      plug list. If a task is accessing multiple disks, eg MD/DM, the
      assumption is wrong. Let blk_attempt_plug_merge() record request from
      the same queue.
      
      V2: use NULL parameter in !mq case. Fix a bug. Add comments in
      blk_attempt_plug_merge to make it less (hopefully) confusion.
      
      Cc: Jens Axboe <axboe@fb.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarShaohua Li <shli@fb.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      5b3f341f
    • Shaohua Li's avatar
      blk-mq: do limited block plug for multiple queue case · f984df1f
      Shaohua Li authored
      
      
      plug is still helpful for workload with IO merge, but it can be harmful
      otherwise especially with multiple hardware queues, as there is
      (supposed) no lock contention in this case and plug can introduce
      latency. For multiple queues, we do limited plug, eg plug only if there
      is request merge. If a request doesn't have merge with following
      request, the requet will be dispatched immediately.
      
      V2: check blk_queue_nomerges() as suggested by Jeff.
      
      Cc: Jens Axboe <axboe@fb.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarShaohua Li <shli@fb.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      f984df1f
    • Shaohua Li's avatar
      blk-mq: avoid re-initialize request which is failed in direct dispatch · 239ad215
      Shaohua Li authored
      
      
      If we directly issue a request and it fails, we use
      blk_mq_merge_queue_io(). But we already assigned bio to a request in
      blk_mq_bio_to_request. blk_mq_merge_queue_io shouldn't run
      blk_mq_bio_to_request again.
      Signed-off-by: default avatarShaohua Li <shli@fb.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      239ad215
    • Jeff Moyer's avatar
      blk-mq: fix plugging in blk_sq_make_request · e6c4438b
      Jeff Moyer authored
      The following appears in blk_sq_make_request:
      
      	/*
      	 * If we have multiple hardware queues, just go directly to
      	 * one of those for sync IO.
      	 */
      
      We clearly don't have multiple hardware queues, here!  This comment was
      introduced with this commit 07068d5b
      
       (blk-mq: split make request
      handler for multi and single queue):
      
          We want slightly different behavior from them:
      
          - On single queue devices, we currently use the per-process plug
            for deferred IO and for merging.
      
          - On multi queue devices, we don't use the per-process plug, but
            we want to go straight to hardware for SYNC IO.
      
      The old code had this:
      
              use_plug = !is_flush_fua && ((q->nr_hw_queues == 1) || !is_sync);
      
      and that was converted to:
      
      	use_plug = !is_flush_fua && !is_sync;
      
      which is not equivalent.  For the single queue case, that second half of
      the && expression is always true.  So, what I think was actually inteded
      follows (and this more closely matches what is done in blk_queue_bio).
      
      V2: delete the 'likely', which should not be a big deal
      Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
      Signed-off-by: default avatarShaohua Li <shli@fb.com>
      Signed-off-by: default avatarJens Axboe <axboe@fb.com>
      e6c4438b