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writeback: cleanup bdi_register

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This patch makes sure we first initialize everything and set the BDI_registered
flag, and only after this we add the bdi to 'bdi_list'. Current code adds the
bdi to the list too early, and as a result I the

WARN(!test_bit(BDI_registered, &bdi->state)

in bdi forker is triggered. Also, it is in general good practice to make things
visible only when they are fully initialized.

Also, this patch does few micro clean-ups:
1. Removes the 'exit' label which does not do anything, just returns. This
   allows to get rid of few braces and 'ret' variable and make the code smaller.
2. If 'kthread_run()' fails, remove the error code it returns, not hard-coded
   '-ENOMEM'. Theoretically, some day 'kthread_run()' can return something
   else. Also, in case of failure it is not necessary to set 'bdi->wb.task' to
   NULL.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Artem Bityutskiy 2010-07-25 14:29:25 +03:00 committed by Jens Axboe
parent 603320239f
commit c284de61db
1 changed files with 11 additions and 19 deletions
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30
mm/backing-dev.c
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@ -511,23 +511,16 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
const char *fmt, ...)
{
va_list args;
int ret = 0;
struct device *dev;
if (bdi->dev) /* The driver needs to use separate queues per device */
goto exit;
return 0;
va_start(args, fmt);
dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
va_end(args);
if (IS_ERR(dev)) {
ret = PTR_ERR(dev);
goto exit;
}
spin_lock_bh(&bdi_lock);
list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
spin_unlock_bh(&bdi_lock);
if (IS_ERR(dev))
return PTR_ERR(dev);
bdi->dev = dev;
@ -541,20 +534,19 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
dev_name(dev));
if (IS_ERR(wb->task)) {
wb->task = NULL;
ret = -ENOMEM;
bdi_remove_from_list(bdi);
goto exit;
}
if (IS_ERR(wb->task))
return PTR_ERR(wb->task);
}
bdi_debug_register(bdi, dev_name(dev));
set_bit(BDI_registered, &bdi->state);
spin_lock_bh(&bdi_lock);
list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
spin_unlock_bh(&bdi_lock);
trace_writeback_bdi_register(bdi);
exit:
return ret;
return 0;
}
EXPORT_SYMBOL(bdi_register);