[5.10-stable,2/3] PCI: Introduce cleanup helper for device reference counts

Commit Message

Lukas Wunner July 30, 2024, 9:30 a.m. UTC

From: Ira Weiny <[e-mail]>

commit ced085ef369af7a2b6da962ec2fbd01339f60693 upstream.

The "goto error" pattern is notorious for introducing subtle resource
leaks. Use the new cleanup.h helpers for PCI device reference counts.

Similar to the new put_device() cleanup helper, __free(put_device),
define the same for PCI devices, __free(pci_dev_put).  These helpers
eliminate the need for "goto free;" patterns. For example, a
'struct pci_dev *' instance declared as:

    struct pci_dev *pdev __free(pci_dev_put) = NULL;

...will automatically call pci_dev_put() if @pdev is non-NULL when @pdev
goes out of scope (automatic variable scope). If a function wants to
invoke pci_dev_put() on error, but return @pdev on success, it can do:

    return no_free_ptr(pdev);

...or:

    return_ptr(pdev);

For potential cleanup opportunity there are 587 open-coded calls to
pci_dev_put() in the kernel with 65 instances within 10 lines of a goto
statement with the CXL driver threatening to add another one.

Cc: Bjorn Helgaas <[e-mail]>
Signed-off-by: Ira Weiny <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
[djbw: rewrite changelog]
Acked-by: Bjorn Helgaas <[e-mail]>
Reviewed-by: Jonathan Cameron <[e-mail]>
Acked-by: Ard Biesheuvel <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>
[lukas: drop DEFINE_GUARD() helper as pci_dev_lock() doesn't exist in v5.10]
Signed-off-by: Lukas Wunner <[e-mail]>
---
 include/linux/pci.h | 1 +
 1 file changed, 1 insertion(+)

Patch

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 30bc462fb196..f497aaf1d032 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1069,6 +1069,7 @@  int pci_get_interrupt_pin(struct pci_dev *dev, struct pci_dev **bridge);
 u8 pci_common_swizzle(struct pci_dev *dev, u8 *pinp);
 struct pci_dev *pci_dev_get(struct pci_dev *dev);
 void pci_dev_put(struct pci_dev *dev);
+DEFINE_FREE(pci_dev_put, struct pci_dev *, if (_T) pci_dev_put(_T))
 void pci_remove_bus(struct pci_bus *b);
 void pci_stop_and_remove_bus_device(struct pci_dev *dev);
 void pci_stop_and_remove_bus_device_locked(struct pci_dev *dev);