[PATCH v3 1/3] devres: provide devm_krealloc()

Bartosz Golaszewski
2020-07-10T16:15:27Z

Implement the managed variant of krealloc(). This function works with
all memory allocated by devm_kmalloc() (or devres functions using it
implicitly like devm_kmemdup(), devm_kstrdup() etc.).

Managed realloc'ed chunks can be manually released with devm_kfree().

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
.../driver-api/driver-model/devres.rst | 1 +
drivers/base/devres.c | 50 +++++++++++++++++++
include/linux/device.h | 2 +
3 files changed, 53 insertions(+)

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index eaaaafc21134..aa08f5162524 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -353,6 +353,7 @@ MEM
devm_kfree()
devm_kmalloc()
devm_kmalloc_array()
+ devm_krealloc()
devm_kmemdup()
devm_kstrdup()
devm_kvasprintf()
diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index ed615d3b9cf1..4b8870ef6a3f 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -837,6 +837,56 @@ void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp)
}
EXPORT_SYMBOL_GPL(devm_kmalloc);

+void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
+{
+ struct devres *old_dr, *new_dr;
+ struct list_head old_head;
+ unsigned long flags;
+ void *ret = NULL;
+ size_t tot_size;
+
+ if (unlikely(!new_size)) {
+ devm_kfree(dev, ptr);
+ return ZERO_SIZE_PTR;
+ }
+
+ if (unlikely(ZERO_OR_NULL_PTR(ptr)))
+ return devm_kmalloc(dev, new_size, gfp);
+
+ if (WARN_ON(is_kernel_rodata((unsigned long)ptr)))
+ /*
+ * We cannot reliably realloc a const string returned by
+ * devm_kstrdup_const().
+ */
+ return NULL;
+
+ if (!check_dr_size(new_size, &tot_size))
+ return NULL;
+
+ spin_lock_irqsave(&dev->devres_lock, flags);
+
+ old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
+ if (WARN_ON(!old_dr))
+ /* Memory chunk not managed or managed by a different device. */
+ goto out;
+
+ old_head = old_dr->node.entry;
+
+ new_dr = krealloc(old_dr, tot_size, gfp);
+ if (!new_dr)
+ goto out;
+
+ if (new_dr != old_dr)
+ list_replace(&old_head, &new_dr->node.entry);
+
+ ret = new_dr->data;
+
+out:
+ spin_unlock_irqrestore(&dev->devres_lock, flags);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(devm_krealloc);
+
/**
* devm_kstrdup - Allocate resource managed space and
* copy an existing string into that.
diff --git a/include/linux/device.h b/include/linux/device.h
index 7322c51e9c0c..f64f40843159 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -206,6 +206,8 @@ int devres_release_group(struct device *dev, void *id);

/* managed devm_k.alloc/kfree for device drivers */
void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp) __malloc;
+void *devm_krealloc(struct device *dev, void *ptr, size_t size,
+ gfp_t gfp) __must_check;
__printf(3, 0) char *devm_kvasprintf(struct device *dev, gfp_t gfp,
const char *fmt, va_list ap) __malloc;
__printf(3, 4) char *devm_kasprintf(struct device *dev, gfp_t gfp,
--
2.26.1