linux-kernel - [PATCH 2/3] flex_arrays: allow zero length flex arrays

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Message-ID: <20110426014537.1740.68472.stgit@paris.rdu.redhat.com>
Date:	Mon, 25 Apr 2011 21:45:37 -0400
From:	Eric Paris <eparis@...hat.com>
To:	dave@...ux.vnet.ibm.com
Cc:	steffen.klassert@...unet.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov,
	sds@...ho.nsa.gov
Subject: [PATCH 2/3] flex_arrays: allow zero length flex arrays

Just like kmalloc will allow one to allocate a 0 length segment of memory
flex arrays should do the same thing.  It should bomb if you try to use
something, but it should at least allow the allocation.

Based-on-patch-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: Eric Paris <eparis@...hat.com>
---

 lib/flex_array.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/lib/flex_array.c b/lib/flex_array.c
index 0c33b24..2554a5f 100644
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -253,9 +253,16 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
 	unsigned int end;
 	struct flex_array_part *part;
 
+	if (!fa->total_nr_elements && !start)
+		return 0;
+	if (start >= fa->total_nr_elements)
+		return -ENOSPC;
+	if (!nr_elements)
+		return 0;
+
 	end = start + nr_elements - 1;
 
-	if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
+	if (end >= fa->total_nr_elements)
 		return -ENOSPC;
 	if (elements_fit_in_base(fa))
 		return 0;
@@ -346,6 +353,8 @@ int flex_array_shrink(struct flex_array *fa)
 	int part_nr;
 	int ret = 0;
 
+	if (!fa->total_nr_elements)
+		return 0;
 	if (elements_fit_in_base(fa))
 		return ret;
 	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {

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