| Message ID | 20190612122557.24158-4-gregkh@linuxfoundation.org (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [1/6] dma: amba-pl08x: no need to cast away call to debugfs_create_file() | expand |
Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes: Hi Greg, > When calling debugfs functions, there is no need to ever check the > return value. The function can work or not, but the code logic should > never do something different based on this. > > Also, because there is no need to save the file dentry, remove the > variable that was saving it as it was never even being used once set. > > Cc: Daniel Mack <daniel@zonque.org> > Cc: Haojian Zhuang <haojian.zhuang@gmail.com> > Cc: Robert Jarzmik <robert.jarzmik@free.fr> > Cc: Vinod Koul <vkoul@kernel.org> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: linux-arm-kernel@lists.infradead.org > Cc: dmaengine@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > --- > drivers/dma/pxa_dma.c | 56 +++++++++---------------------------------- > 1 file changed, 11 insertions(+), 45 deletions(-) > > diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c > index b429642f3e7a..0f698f49ee26 100644 > --- a/drivers/dma/pxa_dma.c > +++ b/drivers/dma/pxa_dma.c > @@ -132,7 +132,6 @@ struct pxad_device { > spinlock_t phy_lock; /* Phy association */ > #ifdef CONFIG_DEBUG_FS > struct dentry *dbgfs_root; > - struct dentry *dbgfs_state; > struct dentry **dbgfs_chan; > #endif > }; > @@ -326,31 +325,18 @@ static struct dentry *pxad_dbg_alloc_chan(struct pxad_device *pdev, > int ch, struct dentry *chandir) > { > char chan_name[11]; > - struct dentry *chan, *chan_state = NULL, *chan_descr = NULL; > - struct dentry *chan_reqs = NULL; > + struct dentry *chan; > void *dt; > > scnprintf(chan_name, sizeof(chan_name), "%d", ch); > chan = debugfs_create_dir(chan_name, chandir); > dt = (void *)&pdev->phys[ch]; > > - if (chan) > - chan_state = debugfs_create_file("state", 0400, chan, dt, > - &chan_state_fops); > - if (chan_state) > - chan_descr = debugfs_create_file("descriptors", 0400, chan, dt, > - &descriptors_fops); > - if (chan_descr) > - chan_reqs = debugfs_create_file("requesters", 0400, chan, dt, > - &requester_chan_fops); > - if (!chan_reqs) > - goto err_state; > + debugfs_create_file("state", 0400, chan, dt, &chan_state_fops); > + debugfs_create_file("descriptors", 0400, chan, dt, &descriptors_fops); > + debugfs_create_file("requesters", 0400, chan, dt, &requester_chan_fops); This is not strictly equivalent. Imagine that the debugfs_create_dir() fails and returns NULL : - in the former case, neither "state", "descriptors" nor "requesters" would be created - in the new code, "state", "descriptors" nor "requesters" will be created in the debugfs root directory Apart from that it looks fine. Cheers.
On Sat, Aug 10, 2019 at 09:27:26PM +0200, Robert Jarzmik wrote: > Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes: > > Hi Greg, > > > When calling debugfs functions, there is no need to ever check the > > return value. The function can work or not, but the code logic should > > never do something different based on this. > > > > Also, because there is no need to save the file dentry, remove the > > variable that was saving it as it was never even being used once set. > > > > Cc: Daniel Mack <daniel@zonque.org> > > Cc: Haojian Zhuang <haojian.zhuang@gmail.com> > > Cc: Robert Jarzmik <robert.jarzmik@free.fr> > > Cc: Vinod Koul <vkoul@kernel.org> > > Cc: Dan Williams <dan.j.williams@intel.com> > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: dmaengine@vger.kernel.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > > drivers/dma/pxa_dma.c | 56 +++++++++---------------------------------- > > 1 file changed, 11 insertions(+), 45 deletions(-) > > > > diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c > > index b429642f3e7a..0f698f49ee26 100644 > > --- a/drivers/dma/pxa_dma.c > > +++ b/drivers/dma/pxa_dma.c > > @@ -132,7 +132,6 @@ struct pxad_device { > > spinlock_t phy_lock; /* Phy association */ > > #ifdef CONFIG_DEBUG_FS > > struct dentry *dbgfs_root; > > - struct dentry *dbgfs_state; > > struct dentry **dbgfs_chan; > > #endif > > }; > > @@ -326,31 +325,18 @@ static struct dentry *pxad_dbg_alloc_chan(struct pxad_device *pdev, > > int ch, struct dentry *chandir) > > { > > char chan_name[11]; > > - struct dentry *chan, *chan_state = NULL, *chan_descr = NULL; > > - struct dentry *chan_reqs = NULL; > > + struct dentry *chan; > > void *dt; > > > > scnprintf(chan_name, sizeof(chan_name), "%d", ch); > > chan = debugfs_create_dir(chan_name, chandir); > > dt = (void *)&pdev->phys[ch]; > > > > - if (chan) > > - chan_state = debugfs_create_file("state", 0400, chan, dt, > > - &chan_state_fops); > > - if (chan_state) > > - chan_descr = debugfs_create_file("descriptors", 0400, chan, dt, > > - &descriptors_fops); > > - if (chan_descr) > > - chan_reqs = debugfs_create_file("requesters", 0400, chan, dt, > > - &requester_chan_fops); > > - if (!chan_reqs) > > - goto err_state; > > + debugfs_create_file("state", 0400, chan, dt, &chan_state_fops); > > + debugfs_create_file("descriptors", 0400, chan, dt, &descriptors_fops); > > + debugfs_create_file("requesters", 0400, chan, dt, &requester_chan_fops); > > This is not strictly equivalent. > Imagine that the debugfs_create_dir() fails and returns NULL : How can that happen? > - in the former case, neither "state", "descriptors" nor "requesters" would be > created > - in the new code, "state", "descriptors" nor "requesters" will be created in > the debugfs root directory I agree, but debugfs_create_dir() does not return a NULL on an error since many kernel releases. Neither can debugfs_create_file() so really this test is not working at all as-is :) thanks, greg k-h
Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes: > On Sat, Aug 10, 2019 at 09:27:26PM +0200, Robert Jarzmik wrote: >> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes: >> >> This is not strictly equivalent. >> Imagine that the debugfs_create_dir() fails and returns NULL : > How can that happen? Well in v5.0-rc1 that could happen ... unfortunately that's also the code I checked ... >> - in the former case, neither "state", "descriptors" nor "requesters" would be >> created >> - in the new code, "state", "descriptors" nor "requesters" will be created in >> the debugfs root directory > > I agree, but debugfs_create_dir() does not return a NULL on an error > since many kernel releases. Neither can debugfs_create_file() so really > this test is not working at all as-is :) Ah yes, you're right, I wasn't aware of the debugfs changes ... But checking a bit further, your original mail is 2 monthes old, and this patch was already merged in v5.2. I probably fell in a time-space anomaly, as I received this mail only a couple of days ago. Have a nice day.
diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c index b429642f3e7a..0f698f49ee26 100644 --- a/drivers/dma/pxa_dma.c +++ b/drivers/dma/pxa_dma.c @@ -132,7 +132,6 @@ struct pxad_device { spinlock_t phy_lock; /* Phy association */ #ifdef CONFIG_DEBUG_FS struct dentry *dbgfs_root; - struct dentry *dbgfs_state; struct dentry **dbgfs_chan; #endif }; @@ -326,31 +325,18 @@ static struct dentry *pxad_dbg_alloc_chan(struct pxad_device *pdev, int ch, struct dentry *chandir) { char chan_name[11]; - struct dentry *chan, *chan_state = NULL, *chan_descr = NULL; - struct dentry *chan_reqs = NULL; + struct dentry *chan; void *dt; scnprintf(chan_name, sizeof(chan_name), "%d", ch); chan = debugfs_create_dir(chan_name, chandir); dt = (void *)&pdev->phys[ch]; - if (chan) - chan_state = debugfs_create_file("state", 0400, chan, dt, - &chan_state_fops); - if (chan_state) - chan_descr = debugfs_create_file("descriptors", 0400, chan, dt, - &descriptors_fops); - if (chan_descr) - chan_reqs = debugfs_create_file("requesters", 0400, chan, dt, - &requester_chan_fops); - if (!chan_reqs) - goto err_state; + debugfs_create_file("state", 0400, chan, dt, &chan_state_fops); + debugfs_create_file("descriptors", 0400, chan, dt, &descriptors_fops); + debugfs_create_file("requesters", 0400, chan, dt, &requester_chan_fops); return chan; - -err_state: - debugfs_remove_recursive(chan); - return NULL; } static void pxad_init_debugfs(struct pxad_device *pdev) @@ -358,40 +344,20 @@ static void pxad_init_debugfs(struct pxad_device *pdev) int i; struct dentry *chandir; - pdev->dbgfs_root = debugfs_create_dir(dev_name(pdev->slave.dev), NULL); - if (IS_ERR(pdev->dbgfs_root) || !pdev->dbgfs_root) - goto err_root; - - pdev->dbgfs_state = debugfs_create_file("state", 0400, pdev->dbgfs_root, - pdev, &state_fops); - if (!pdev->dbgfs_state) - goto err_state; - pdev->dbgfs_chan = - kmalloc_array(pdev->nr_chans, sizeof(*pdev->dbgfs_state), + kmalloc_array(pdev->nr_chans, sizeof(struct dentry *), GFP_KERNEL); if (!pdev->dbgfs_chan) - goto err_alloc; + return; + + pdev->dbgfs_root = debugfs_create_dir(dev_name(pdev->slave.dev), NULL); + + debugfs_create_file("state", 0400, pdev->dbgfs_root, pdev, &state_fops); chandir = debugfs_create_dir("channels", pdev->dbgfs_root); - if (!chandir) - goto err_chandir; - for (i = 0; i < pdev->nr_chans; i++) { + for (i = 0; i < pdev->nr_chans; i++) pdev->dbgfs_chan[i] = pxad_dbg_alloc_chan(pdev, i, chandir); - if (!pdev->dbgfs_chan[i]) - goto err_chans; - } - - return; -err_chans: -err_chandir: - kfree(pdev->dbgfs_chan); -err_alloc: -err_state: - debugfs_remove_recursive(pdev->dbgfs_root); -err_root: - pr_err("pxad: debugfs is not available\n"); } static void pxad_cleanup_debugfs(struct pxad_device *pdev)
When calling debugfs functions, there is no need to ever check the return value. The function can work or not, but the code logic should never do something different based on this. Also, because there is no need to save the file dentry, remove the variable that was saving it as it was never even being used once set. Cc: Daniel Mack <daniel@zonque.org> Cc: Haojian Zhuang <haojian.zhuang@gmail.com> Cc: Robert Jarzmik <robert.jarzmik@free.fr> Cc: Vinod Koul <vkoul@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: linux-arm-kernel@lists.infradead.org Cc: dmaengine@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/dma/pxa_dma.c | 56 +++++++++---------------------------------- 1 file changed, 11 insertions(+), 45 deletions(-)