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Subject[PATCH] mm: Make kvfree safe to call
Date
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Since vfree() can sleep, calling kvfree() from contexts where sleeping
is not permitted (eg holding a spinlock) is a bit of a lottery whether
it'll work. Introduce kvfree_safe() for situations where we know we can
sleep, but make kvfree() safe by default.

Reported-by: Jeff Layton <jlayton@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Luis Henriques <lhenriques@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
mm/util.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index bab284d69c8c..992f0332dced 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -470,6 +470,28 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
}
EXPORT_SYMBOL(kvmalloc_node);

+/**
+ * kvfree_fast() - Free memory.
+ * @addr: Pointer to allocated memory.
+ *
+ * kvfree_fast frees memory allocated by any of vmalloc(), kmalloc() or
+ * kvmalloc(). It is slightly more efficient to use kfree() or vfree() if
+ * you are certain that you know which one to use.
+ *
+ * Context: Either preemptible task context or not-NMI interrupt. Must not
+ * hold a spinlock as it can sleep.
+ */
+void kvfree_fast(const void *addr)
+{
+ might_sleep();
+
+ if (is_vmalloc_addr(addr))
+ vfree(addr);
+ else
+ kfree(addr);
+}
+EXPORT_SYMBOL(kvfree_fast);
+
/**
* kvfree() - Free memory.
* @addr: Pointer to allocated memory.
@@ -478,12 +500,12 @@ EXPORT_SYMBOL(kvmalloc_node);
* It is slightly more efficient to use kfree() or vfree() if you are certain
* that you know which one to use.
*
- * Context: Either preemptible task context or not-NMI interrupt.
+ * Context: Any context except NMI.
*/
void kvfree(const void *addr)
{
if (is_vmalloc_addr(addr))
- vfree(addr);
+ vfree_atomic(addr);
else
kfree(addr);
}
--
2.20.1
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