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    Subject[PATCH v2 47/47] mm: shrinker: convert shrinker_rwsem to mutex
    Date
    Now there are no readers of shrinker_rwsem, so we can simply replace it
    with mutex lock.

    Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
    ---
    drivers/md/dm-cache-metadata.c | 2 +-
    fs/super.c | 2 +-
    mm/shrinker.c | 16 ++++++++--------
    mm/shrinker_debug.c | 14 +++++++-------
    4 files changed, 17 insertions(+), 17 deletions(-)

    diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
    index acffed750e3e..9e0c69958587 100644
    --- a/drivers/md/dm-cache-metadata.c
    +++ b/drivers/md/dm-cache-metadata.c
    @@ -1828,7 +1828,7 @@ int dm_cache_metadata_abort(struct dm_cache_metadata *cmd)
    * Replacement block manager (new_bm) is created and old_bm destroyed outside of
    * cmd root_lock to avoid ABBA deadlock that would result (due to life-cycle of
    * shrinker associated with the block manager's bufio client vs cmd root_lock).
    - * - must take shrinker_rwsem without holding cmd->root_lock
    + * - must take shrinker_mutex without holding cmd->root_lock
    */
    new_bm = dm_block_manager_create(cmd->bdev, DM_CACHE_METADATA_BLOCK_SIZE << SECTOR_SHIFT,
    CACHE_MAX_CONCURRENT_LOCKS);
    diff --git a/fs/super.c b/fs/super.c
    index 04643fd80886..602cf54eb7da 100644
    --- a/fs/super.c
    +++ b/fs/super.c
    @@ -54,7 +54,7 @@ static char *sb_writers_name[SB_FREEZE_LEVELS] = {
    * One thing we have to be careful of with a per-sb shrinker is that we don't
    * drop the last active reference to the superblock from within the shrinker.
    * If that happens we could trigger unregistering the shrinker from within the
    - * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
    + * shrinker path and that leads to deadlock on the shrinker_mutex. Hence we
    * take a passive reference to the superblock to avoid this from occurring.
    */
    static unsigned long super_cache_scan(struct shrinker *shrink,
    diff --git a/mm/shrinker.c b/mm/shrinker.c
    index 90c045620fe3..5c4546d2c234 100644
    --- a/mm/shrinker.c
    +++ b/mm/shrinker.c
    @@ -7,7 +7,7 @@
    #include <trace/events/vmscan.h>

    LIST_HEAD(shrinker_list);
    -DECLARE_RWSEM(shrinker_rwsem);
    +DEFINE_MUTEX(shrinker_mutex);
    DEFINE_SPINLOCK(shrinker_lock);

    #ifdef CONFIG_MEMCG
    @@ -80,7 +80,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
    int nid, ret = 0;
    int array_size = 0;

    - down_write(&shrinker_rwsem);
    + mutex_lock(&shrinker_mutex);
    array_size = shrinker_unit_size(shrinker_nr_max);
    for_each_node(nid) {
    info = kvzalloc_node(sizeof(*info) + array_size, GFP_KERNEL, nid);
    @@ -91,7 +91,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
    goto err;
    rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
    }
    - up_write(&shrinker_rwsem);
    + mutex_unlock(&shrinker_mutex);

    return ret;

    @@ -104,7 +104,7 @@ static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
    int nid)
    {
    return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
    - lockdep_is_held(&shrinker_rwsem));
    + lockdep_is_held(&shrinker_mutex));
    }

    static struct shrinker_info *shrinker_info_rcu(struct mem_cgroup *memcg,
    @@ -158,7 +158,7 @@ static int expand_shrinker_info(int new_id)
    int new_size, old_size = 0;
    struct mem_cgroup *memcg;

    - down_write(&shrinker_rwsem);
    + mutex_lock(&shrinker_mutex);

    if (!root_mem_cgroup)
    goto out;
    @@ -179,7 +179,7 @@ static int expand_shrinker_info(int new_id)
    if (!ret)
    shrinker_nr_max = new_nr_max;

    - up_write(&shrinker_rwsem);
    + mutex_unlock(&shrinker_mutex);

    return ret;
    }
    @@ -303,7 +303,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
    parent = root_mem_cgroup;

    /* Prevent from concurrent shrinker_info expand */
    - down_write(&shrinker_rwsem);
    + mutex_lock(&shrinker_mutex);
    for_each_node(nid) {
    child_info = shrinker_info_protected(memcg, nid);
    parent_info = shrinker_info_protected(parent, nid);
    @@ -316,7 +316,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
    }
    }
    }
    - up_write(&shrinker_rwsem);
    + mutex_unlock(&shrinker_mutex);
    }
    #else
    static int shrinker_memcg_alloc(struct shrinker *shrinker)
    diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
    index badda35464c3..44b620b1919d 100644
    --- a/mm/shrinker_debug.c
    +++ b/mm/shrinker_debug.c
    @@ -8,7 +8,7 @@
    #include <linux/rculist.h>

    /* defined in vmscan.c */
    -extern struct rw_semaphore shrinker_rwsem;
    +extern struct mutex shrinker_mutex;
    extern struct list_head shrinker_list;

    static DEFINE_IDA(shrinker_debugfs_ida);
    @@ -168,7 +168,7 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
    if (!shrinker_debugfs_root)
    return 0;

    - down_write(&shrinker_rwsem);
    + mutex_lock(&shrinker_mutex);
    if (shrinker->debugfs_entry)
    goto fail;

    @@ -196,7 +196,7 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
    &shrinker_debugfs_scan_fops);

    fail:
    - up_write(&shrinker_rwsem);
    + mutex_unlock(&shrinker_mutex);
    return ret;
    }

    @@ -215,7 +215,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
    if (!new)
    return -ENOMEM;

    - down_write(&shrinker_rwsem);
    + mutex_lock(&shrinker_mutex);

    old = shrinker->name;
    shrinker->name = new;
    @@ -233,7 +233,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
    shrinker->debugfs_entry = entry;
    }

    - up_write(&shrinker_rwsem);
    + mutex_unlock(&shrinker_mutex);

    kfree_const(old);

    @@ -246,7 +246,7 @@ struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
    {
    struct dentry *entry = shrinker->debugfs_entry;

    - down_write(&shrinker_rwsem);
    + mutex_lock(&shrinker_mutex);
    kfree_const(shrinker->name);
    shrinker->name = NULL;

    @@ -257,7 +257,7 @@ struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
    */
    smp_wmb();
    shrinker->debugfs_entry = NULL;
    - up_write(&shrinker_rwsem);
    + mutex_unlock(&shrinker_mutex);

    return entry;
    }
    --
    2.30.2
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