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    SubjectRe: [PATCH 1/7] USB: gadget: file_storage: put_device() in error recovery
    On Tue, 26 Oct 2010 16:09:27 +0200, Alan Stern <stern@rowland.harvard.edu> wrote:

    > On Tue, 26 Oct 2010, Michal Nazarewicz wrote:
    >> This commit fixes some issues with File-backed Storage Gadget
    >> error recovery when registering LUN's devices.
    >>
    >> First of all, when device_register() fails the device still
    >> needs to be put. However, because lun_release() decreases
    >> fsg->ref reference counter the counter must be incremented
    >> beforehand.
    >
    > Correct.
    >
    >> Second of all, after any of the device_create_file()s fails,
    >> device_unregister() is called which in turn (indirectly) calls
    >> lun_release() which decrements fsg->ref. So, again, the
    >> reference counter must be incremented beforehand.
    >
    > Correct.
    >
    >> Lastly, if the first or the second device_create_file()
    >> succeeds, the files are never removed. To fix it,
    >> device_remove_file() needs to be called. This is done by
    >> simply marking LUN as registered prior to creating files so
    >> that fsg_unbind() can handle removing files.
    >
    > Correct.


    >> Hope I'm not late for 37?
    >
    > No doubt it is too late to get into the merge window.

    Ah, yes, that what I meant. I was hoping to get the whole set in -rc1, since
    some of the patches are purely coding style fixes.


    >> diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
    >> index d4fdf65..e0504a1 100644
    >> --- a/drivers/usb/gadget/file_storage.c
    >> +++ b/drivers/usb/gadget/file_storage.c
    >> @@ -3392,21 +3392,19 @@ static int __init fsg_bind(struct usb_gadget *gadget)
    >> dev_set_name(&curlun->dev,"%s-lun%d",
    >> dev_name(&gadget->dev), i);
    >>
    >> - if ((rc = device_register(&curlun->dev)) != 0) {
    >> + kref_get(&fsg->ref);
    >> + rc = device_register(&curlun->dev);
    >> + if (rc) {
    >> INFO(fsg, "failed to register LUN%d: %d\n", i, rc);
    >> - goto out;
    >> - }
    >> - if ((rc = device_create_file(&curlun->dev,
    >> - &dev_attr_ro)) != 0 ||
    >> - (rc = device_create_file(&curlun->dev,
    >> - &dev_attr_nofua)) != 0 ||
    >> - (rc = device_create_file(&curlun->dev,
    >> - &dev_attr_file)) != 0) {
    >> - device_unregister(&curlun->dev);
    >> + put_device(&curlun->dev);
    >> goto out;
    >> }
    >> curlun->registered = 1;
    >> - kref_get(&fsg->ref);
    >> +
    >> + if ((rc = device_create_file(&curlun->dev, &dev_attr_ro)) ||
    >> + (rc = device_create_file(&curlun->dev, &dev_attr_nofua)) ||
    >> + (rc = device_create_file(&curlun->dev, &dev_attr_file)))
    >> + goto out;
    >
    > As long as you're changing these anyway, you may as well use the style
    > most developers seem to prefer:
    >
    > rc = device_create_file(&curlun->dev, &dev_attr_ro);
    > if (rc)
    > goto out;
    > ...

    But then it'd be total of 9 lines consisting of three 3-line ifs. I decided
    that it would be more readable with a single if even though it is not compliant
    with coding style. What do you think? I can just resend it.

    > After all, you did the same thing in the device_register() call above.
    > Apart from this small matter, ACK.

    Thanks.

    --
    Best regards, _ _
    | Humble Liege of Serenely Enlightened Majesty of o' \,=./ `o
    | Computer Science, Michał "mina86" Nazarewicz (o o)
    +----[mina86*mina86.com]---[mina86*jabber.org]----ooO--(_)--Ooo--
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