lkml.org 
[lkml]   [2019]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH v3 4/5] writeback, memcg: Implement cgroup_writeback_by_id()
    Implement cgroup_writeback_by_id() which initiates cgroup writeback
    from bdi and memcg IDs. This will be used by memcg foreign inode
    flushing.

    v2: Use wb_get_lookup() instead of wb_get_create() to avoid creating
    spurious wbs.

    v3: Interpret 0 @nr as 1.25 * nr_dirty to implement best-effort
    flushing while avoding possible livelocks.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    fs/fs-writeback.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/writeback.h | 2 +
    2 files changed, 85 insertions(+)

    --- a/fs/fs-writeback.c
    +++ b/fs/fs-writeback.c
    @@ -892,6 +892,89 @@ restart:
    }

    /**
    + * cgroup_writeback_by_id - initiate cgroup writeback from bdi and memcg IDs
    + * @bdi_id: target bdi id
    + * @memcg_id: target memcg css id
    + * @nr_pages: number of pages to write, 0 for best-effort dirty flushing
    + * @reason: reason why some writeback work initiated
    + * @done: target wb_completion
    + *
    + * Initiate flush of the bdi_writeback identified by @bdi_id and @memcg_id
    + * with the specified parameters.
    + */
    +int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr,
    + enum wb_reason reason, struct wb_completion *done)
    +{
    + struct backing_dev_info *bdi;
    + struct cgroup_subsys_state *memcg_css;
    + struct bdi_writeback *wb;
    + struct wb_writeback_work *work;
    + int ret;
    +
    + /* lookup bdi and memcg */
    + bdi = bdi_get_by_id(bdi_id);
    + if (!bdi)
    + return -ENOENT;
    +
    + rcu_read_lock();
    + memcg_css = css_from_id(memcg_id, &memory_cgrp_subsys);
    + if (memcg_css && !css_tryget(memcg_css))
    + memcg_css = NULL;
    + rcu_read_unlock();
    + if (!memcg_css) {
    + ret = -ENOENT;
    + goto out_bdi_put;
    + }
    +
    + /*
    + * And find the associated wb. If the wb isn't there already
    + * there's nothing to flush, don't create one.
    + */
    + wb = wb_get_lookup(bdi, memcg_css);
    + if (!wb) {
    + ret = -ENOENT;
    + goto out_css_put;
    + }
    +
    + /*
    + * If @nr is zero, the caller is attempting to write out most of
    + * the currently dirty pages. Let's take the current dirty page
    + * count and inflate it by 25% which should be large enough to
    + * flush out most dirty pages while avoiding getting livelocked by
    + * concurrent dirtiers.
    + */
    + if (!nr) {
    + unsigned long filepages, headroom, dirty, writeback;
    +
    + mem_cgroup_wb_stats(wb, &filepages, &headroom, &dirty,
    + &writeback);
    + nr = dirty * 10 / 8;
    + }
    +
    + /* issue the writeback work */
    + work = kzalloc(sizeof(*work), GFP_NOWAIT | __GFP_NOWARN);
    + if (work) {
    + work->nr_pages = nr;
    + work->sync_mode = WB_SYNC_NONE;
    + work->range_cyclic = 1;
    + work->reason = reason;
    + work->done = done;
    + work->auto_free = 1;
    + wb_queue_work(wb, work);
    + ret = 0;
    + } else {
    + ret = -ENOMEM;
    + }
    +
    + wb_put(wb);
    +out_css_put:
    + css_put(memcg_css);
    +out_bdi_put:
    + bdi_put(bdi);
    + return ret;
    +}
    +
    +/**
    * cgroup_writeback_umount - flush inode wb switches for umount
    *
    * This function is called when a super_block is about to be destroyed and
    --- a/include/linux/writeback.h
    +++ b/include/linux/writeback.h
    @@ -217,6 +217,8 @@ void wbc_attach_and_unlock_inode(struct
    void wbc_detach_inode(struct writeback_control *wbc);
    void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
    size_t bytes);
    +int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr_pages,
    + enum wb_reason reason, struct wb_completion *done);
    void cgroup_writeback_umount(void);

    /**
    \
     
     \ /
      Last update: 2019-08-21 23:02    [W:2.612 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site