| Message ID | 20250319105506.083538907@linutronix.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | genirq/msi: Spring cleaning | expand |
On Wed, 2025-03-19 at 11:56 +0100, Thomas Gleixner wrote: > In cases where an allocation is consumed by another function, the > allocation needs to be retained on success or freed on failure. The > code > pattern is usually: > > struct foo *f = kzalloc(sizeof(*f), GFP_KERNEL); > struct bar *b; > > ,,, > // Initialize f > ... > if (ret) > goto free; > ... > bar = bar_create(f); > if (!bar) { > ret = -ENOMEM; > goto free; > } > ... > return 0; > free: > kfree(f); > return ret; > > This prevents using __free(kfree) on @f because there is no canonical > way to tell the cleanup code that the allocation should not be freed. > > Abusing no_free_ptr() by force ignoring the return value is not > really a sensible option either. > > Provide an explicit macro retain_ptr(), which NULLs the cleanup > pointer. That makes it easy to analyze and reason about. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > Cc: Peter Zijlstra <peterz@infradead.org> > --- > V4: Cast to void so can't be used as return_ptr() replacement - James Reviewed-by: James Bottomley <James.Bottomley@HansenPartnership.com>
--- a/include/linux/cleanup.h +++ b/include/linux/cleanup.h @@ -216,6 +216,22 @@ const volatile void * __must_check_fn(co #define return_ptr(p) return no_free_ptr(p) +/* + * Only for situations where an allocation is handed in to another function + * and consumed by that function on success. + * + * struct foo *f __free(kfree) = kzalloc(sizeof(*f), GFP_KERNEL); + * + * setup(f); + * if (some_condition) + * return -EINVAL; + * .... + * ret = bar(f); + * if (!ret) + * retain_ptr(f); + * return ret; + */ +#define retain_ptr(p) ((void)__get_and_null(p, NULL)) /* * DEFINE_CLASS(name, type, exit, init, init_args...):
In cases where an allocation is consumed by another function, the allocation needs to be retained on success or freed on failure. The code pattern is usually: struct foo *f = kzalloc(sizeof(*f), GFP_KERNEL); struct bar *b; ,,, // Initialize f ... if (ret) goto free; ... bar = bar_create(f); if (!bar) { ret = -ENOMEM; goto free; } ... return 0; free: kfree(f); return ret; This prevents using __free(kfree) on @f because there is no canonical way to tell the cleanup code that the allocation should not be freed. Abusing no_free_ptr() by force ignoring the return value is not really a sensible option either. Provide an explicit macro retain_ptr(), which NULLs the cleanup pointer. That makes it easy to analyze and reason about. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Peter Zijlstra <peterz@infradead.org> --- V4: Cast to void so can't be used as return_ptr() replacement - James --- include/linux/cleanup.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)