fs: remove default_backing_dev_info

Now that default_backing_dev_info is not used for writeback purposes we can
git rid of it easily:

 - instead of using it's name for tracing unregistered bdi we just use
   "unknown"
 - btrfs and ceph can just assign the default read ahead window themselves
   like several other filesystems already do.
 - we can assign noop_backing_dev_info as the default one in alloc_super.
   All filesystems already either assigned their own or
   noop_backing_dev_info.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1ec872e3a9265ff4dd5020dfbe686dd870ae8a3b..1afb18226da82c9bff5870c2f7770b164d7f68b2 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1719,7 +1719,7 @@ static int setup_bdi(struct btrfs_fs_info *info, struct backing_dev_info *bdi)
        if (err)
                return err;
 
-       bdi->ra_pages   = default_backing_dev_info.ra_pages;
+       bdi->ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE;
        bdi->congested_fn       = btrfs_congested_fn;
        bdi->congested_data     = info;
        return 0;

diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index e350cc1611e4d0ac842d99d76ba324b98659ef44..5ae62587a71d5c7e4e413e1252572707433aaf7b 100644 (file)
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -899,7 +899,7 @@ static int ceph_register_bdi(struct super_block *sb,
                        >> PAGE_SHIFT;
        else
                fsc->backing_dev_info.ra_pages =
-                       default_backing_dev_info.ra_pages;
+                       VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE;
 
        err = bdi_register(&fsc->backing_dev_info, NULL, "ceph-%ld",
                           atomic_long_inc_return(&bdi_seq));

diff --git a/fs/super.c b/fs/super.c
index eae088f6aaaeb6e8a3380adad19fb66feebe9905..3b4dadafdd6055be4d84feeaa381cc6dcd1fcb0b 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -185,8 +185,8 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
        }
        init_waitqueue_head(&s->s_writers.wait);
        init_waitqueue_head(&s->s_writers.wait_unfrozen);
+       s->s_bdi = &noop_backing_dev_info;
        s->s_flags = flags;
-       s->s_bdi = &default_backing_dev_info;
        INIT_HLIST_NODE(&s->s_instances);
        INIT_HLIST_BL_HEAD(&s->s_anon);
        INIT_LIST_HEAD(&s->s_inodes);
@@ -863,10 +863,7 @@ EXPORT_SYMBOL(free_anon_bdev);
 
 int set_anon_super(struct super_block *s, void *data)
 {
-       int error = get_anon_bdev(&s->s_dev);
-       if (!error)
-               s->s_bdi = &noop_backing_dev_info;
-       return error;
+       return get_anon_bdev(&s->s_dev);
 }
 
 EXPORT_SYMBOL(set_anon_super);
@@ -1111,7 +1108,6 @@ mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
        sb = root->d_sb;
        BUG_ON(!sb);
        WARN_ON(!sb->s_bdi);
-       WARN_ON(sb->s_bdi == &default_backing_dev_info);
        sb->s_flags |= MS_BORN;
 
        error = security_sb_kern_mount(sb, flags, secdata);

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index ed59dee03a7133a1816851fdd1664520d5a6bb52..d94077fea1f8a2f5f811f744eb825501047113fe 100644 (file)
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -241,7 +241,6 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
        (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
 
-extern struct backing_dev_info default_backing_dev_info;
 extern struct backing_dev_info noop_backing_dev_info;
 
 int writeback_in_progress(struct backing_dev_info *bdi);

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 74f5207bd09070b8d493d9c975e753ac0c9817d4..0e9310905413ffc4bbdbdeebc91a17edde30959d 100644 (file)
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -156,10 +156,8 @@ DECLARE_EVENT_CLASS(writeback_work_class,
                __field(int, reason)
        ),
        TP_fast_assign(
-               struct device *dev = bdi->dev;
-               if (!dev)
-                       dev = default_backing_dev_info.dev;
-               strncpy(__entry->name, dev_name(dev), 32);
+               strncpy(__entry->name,
+                       bdi->dev ? dev_name(bdi->dev) : "(unknown)", 32);
                __entry->nr_pages = work->nr_pages;
                __entry->sb_dev = work->sb ? work->sb->s_dev : 0;
                __entry->sync_mode = work->sync_mode;

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 1725adb242e09d5ce77a6fcaa3050e4a83dc215f..7690ec77c72297de1c47e5cc3e5b9ebaa7c429a6 100644 (file)
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -14,12 +14,6 @@
 
 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
 
-struct backing_dev_info default_backing_dev_info = {
-       .name           = "default",
-       .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
-};
-EXPORT_SYMBOL_GPL(default_backing_dev_info);
-
 struct backing_dev_info noop_backing_dev_info = {
        .name           = "noop",
        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
@@ -250,9 +244,6 @@ static int __init default_bdi_init(void)
        if (!bdi_wq)
                return -ENOMEM;
 
-       err = bdi_init(&default_backing_dev_info);
-       if (!err)
-               bdi_register(&default_backing_dev_info, NULL, "default");
        err = bdi_init(&noop_backing_dev_info);
 
        return err;