Messages in this thread | | | Subject | Re: [PATCH 3/8] bdi: add a ->dev_name field to struct backing_dev_info | From | Bart Van Assche <> | Date | Sun, 19 Apr 2020 08:29:21 -0700 |
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On 4/19/20 12:58 AM, Christoph Hellwig wrote: > On Sat, Apr 18, 2020 at 08:40:20AM -0700, Bart Van Assche wrote: >>> This can have a sideeffect not only bdi->dev_name will be truncated to 64 >>> chars (which generally doesn't matter) but possibly also kobject name will >>> be truncated in the same way. Which may have user visible effects. E.g. >>> for fs/vboxsf 64 chars need not be enough. So shouldn't we rather do it the >>> other way around - i.e., let device_create_vargs() create the device name >>> and then copy to bdi->dev_name whatever fits? >> >> How about using kvasprintf() instead of vsnprintf()? > > That is what v1 did, see the thread in response to that on why it isn't > a good idea.
Are you perhaps referring to patch "[PATCH 3/8] bdi: add a ->dev_name field to struct backing_dev_info" (https://lore.kernel.org/linux-block/20200416071519.807660-4-hch@lst.de/) and also to the replies to that patch? This is what I found in the replies: "When driver try to to re-register bdi but without release_bdi(), the old dev_name will be cover directly by the newer in bdi_register_va(). So, I am not sure whether it can cause memory leak for bdi->dev_name."
Has it been considered to avoid that leak by freeing bdi->dev_name from unregister_bdi(), e.g. as follows?
void bdi_unregister(struct backing_dev_info *bdi) { + char *dev_name;
/* make sure nobody finds us on the bdi_list anymore */ bdi_remove_from_list(bdi); wb_shutdown(&bdi->wb); cgwb_bdi_unregister(bdi);
if (bdi->dev) { bdi_debug_unregister(bdi); device_unregister(bdi->dev); bdi->dev = NULL; + dev_name = bdi->dev_name; + bdi->dev_name = "(unregistered)"; + kfree(dev_name); }
if (bdi->owner) { put_device(bdi->owner); bdi->owner = NULL; } }
Thanks,
Bart.
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