Re: [PATCH] firmware: Be a bit more verbose about direct firmwareloading failure

[Neil Horman]

On Wed, Sep 11, 2013 at 07:54:28PM +0800, Ming Lei wrote:
> On Sat, Sep 7, 2013 at 3:36 AM, Neil Horman <nhorman@xxxxxxxxxxxxx> wrote:
> > The direct firmware loading interface is a bit quiet about failures.  Failures
> 
> Because there are several pre-defined search paths, and generally the
> requested firmware only exists in one of these paths.
> 
This is true, but you'll note this patch doesn't make any noise in the event
that a firmware isn't found until all the search paths are exhausted.  I didn't
consider this "unexpected".

> > that occur during loading are masked if firmware exists in multiple locations,
> > and may be masked entirely in the event that we fall back to the user mode
> 
> You still can figure out the request falls back to user mode loading since we
> have the "firmware: direct-loading firmware %s" log.
> 
Yes, but you're looking at it backwards, that only prints out if the direct load
works.  If it doesn't, you get silence, which is bad.

> > helper code.  It would be nice to see some of the more unexpected errors get
> 
> What are the unexpected errors?
> 
If you get a short read in the direct load path for example, or if someone
mounts an nfs share over the firmware search path and you get an ESTALE.
Alternatively, if the vmalloc fails during the direct load path, these would be
"unexpected" errors

> > logged, so in the event that you expect the direct firmware loader to work (like
> > if CONFIG_FW_LOADER_USER_HELPER is enabled), and something goes wrong, you can
> > figure out what happened.
> 
> Looks we didn't meet this case, do you have real examples?
> 
Yeah, we had a vmalloc failure in the direct load path, and unknowingly had
forgot to configure CONFIG_FW_LOADER_USER_HELPER, so the module load failed with
an ENOENT, even though the firmware was clearly present on the filesystem.  This
patch helped us track that down.

Neil

> >
> > Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
> > CC: Ming Lei <ming.lei@xxxxxxxxxxxxx>
> > CC: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/base/firmware_class.c | 38 +++++++++++++++++++++++++-------------
> >  1 file changed, 25 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> > index 10a4467..eb8fb94 100644
> > --- a/drivers/base/firmware_class.c
> > +++ b/drivers/base/firmware_class.c
> > @@ -282,31 +282,35 @@ static noinline_for_stack long fw_file_size(struct file *file)
> >         return st.size;
> >  }
> >
> > -static bool fw_read_file_contents(struct file *file, struct firmware_buf *fw_buf)
> > +static int fw_read_file_contents(struct file *file, struct firmware_buf *fw_buf)
> >  {
> >         long size;
> >         char *buf;
> > +       int rc;
> >
> >         size = fw_file_size(file);
> >         if (size <= 0)
> > -               return false;
> > +               return -EINVAL;
> >         buf = vmalloc(size);
> >         if (!buf)
> > -               return false;
> > -       if (kernel_read(file, 0, buf, size) != size) {
> > +               return -ENOMEM;
> > +       rc = kernel_read(file, 0, buf, size);
> > +       if (rc != size) {
> > +               if (rc > 0)
> > +                       rc = -EIO;
> >                 vfree(buf);
> > -               return false;
> > +               return rc;
> >         }
> >         fw_buf->data = buf;
> >         fw_buf->size = size;
> > -       return true;
> > +       return 0;
> >  }
> >
> > -static bool fw_get_filesystem_firmware(struct device *device,
> > +static int fw_get_filesystem_firmware(struct device *device,
> >                                        struct firmware_buf *buf)
> >  {
> >         int i;
> > -       bool success = false;
> > +       int rc = -ENOENT;
> >         char *path = __getname();
> >
> >         for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
> > @@ -321,14 +325,17 @@ static bool fw_get_filesystem_firmware(struct device *device,
> >                 file = filp_open(path, O_RDONLY, 0);
> >                 if (IS_ERR(file))
> >                         continue;
> > -               success = fw_read_file_contents(file, buf);
> > +               rc = fw_read_file_contents(file, buf);
> >                 fput(file);
> > -               if (success)
> > +               if (rc)
> > +                       dev_warn(device, "firmware, attempted to load %s, but failed with error %d\n",
> > +                               path, rc);
> 
> The above may introduce noises.
> 
> > +               else
> >                         break;
> >         }
> >         __putname(path);
> >
> > -       if (success) {
> > +       if (!rc) {
> >                 dev_dbg(device, "firmware: direct-loading firmware %s\n",
> >                         buf->fw_id);
> >                 mutex_lock(&fw_lock);
> > @@ -337,7 +344,7 @@ static bool fw_get_filesystem_firmware(struct device *device,
> >                 mutex_unlock(&fw_lock);
> >         }
> >
> > -       return success;
> > +       return rc;
> >  }
> >
> >  /* firmware holds the ownership of pages */
> > @@ -1086,9 +1093,14 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
> >                 }
> >         }
> >
> > -       if (!fw_get_filesystem_firmware(device, fw->priv))
> > +       ret = fw_get_filesystem_firmware(device, fw->priv);
> > +       if (ret) {
> > +               dev_warn(device, "Direct firmware load failed with error %d\n",
> > +                        ret);
> > +               dev_warn(device, "Falling back to user helper\n");
> 
> You should merge the two warnings to into one?
> 
> >                 ret = fw_load_from_user_helper(fw, name, device,
> >                                                uevent, nowait, timeout);
> > +       }
> >
> >         /* don't cache firmware handled without uevent */
> >         if (!ret)
> 
> 
> Thanks,
> --
> Ming Lei
> 
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