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Date: Tue, 22 Dec 2015 17:54:24 -0700
From: Toshi Kani <toshi.kani@....com>
To: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, bp@...en8.de
Cc: stsp@...t.ru, x86@...nel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
Toshi Kani <toshi.kani@....com>
Subject: [PATCH v2 2/2] x86/mm/pat: Change free_memtype() to support shrinking case
Using mremap() to shrink the map size of a VM_PFNMAP range causes
the following error message, and leaves the pfn range allocated.
x86/PAT: test:3493 freeing invalid memtype [mem 0x483200000-0x4863fffff]
This is because rbt_memtype_erase(), called from free_memtype()
with spin_lock held, only supports to free a whole memtype node in
memtype_rbroot. Therefore, this patch changes rbt_memtype_erase()
to support a request that shrinks the size of a memtype node for
mremap().
memtype_rb_exact_match() is renamed to memtype_rb_match(), and
is enhanced to support EXACT_MATCH and END_MATH in @match_type.
Since the memtype_rbroot tree allows overlapping ranges,
rbt_memtype_erase() checks with EXACT_MATCH first, i.e. free
a whole node for the munmap case. If no such entry is found,
it then checks with END_MATCH, i.e. shrink the size of a node
from the end for the mremap case.
On the mremap case, rbt_memtype_erase() proceeds in two steps,
1) remove the node, and then 2) insert the updated node. This
allows proper update of augmented values, subtree_max_end, in
the tree.
Link: http://lkml.kernel.org/r/<1446072663.20657.150.camel@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Borislav Petkov <bp@...e.de>
Signed-off-by: Toshi Kani <toshi.kani@....com>
---
arch/x86/mm/pat.c | 2 +-
arch/x86/mm/pat_rbtree.c | 52 ++++++++++++++++++++++++++++++++++++++--------
2 files changed, 44 insertions(+), 10 deletions(-)
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 1aca073..031782e 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -586,7 +586,7 @@ int free_memtype(u64 start, u64 end)
entry = rbt_memtype_erase(start, end);
spin_unlock(&memtype_lock);
- if (!entry) {
+ if (IS_ERR(entry)) {
pr_info("x86/PAT: %s:%d freeing invalid memtype [mem %#010Lx-%#010Lx]\n",
current->comm, current->pid, start, end - 1);
return -EINVAL;
diff --git a/arch/x86/mm/pat_rbtree.c b/arch/x86/mm/pat_rbtree.c
index 6393108..2f77022 100644
--- a/arch/x86/mm/pat_rbtree.c
+++ b/arch/x86/mm/pat_rbtree.c
@@ -98,8 +98,13 @@ static struct memtype *memtype_rb_lowest_match(struct rb_root *root,
return last_lower; /* Returns NULL if there is no overlap */
}
-static struct memtype *memtype_rb_exact_match(struct rb_root *root,
- u64 start, u64 end)
+enum {
+ MEMTYPE_EXACT_MATCH = 0,
+ MEMTYPE_END_MATCH = 1
+};
+
+static struct memtype *memtype_rb_match(struct rb_root *root,
+ u64 start, u64 end, int match_type)
{
struct memtype *match;
@@ -107,7 +112,12 @@ static struct memtype *memtype_rb_exact_match(struct rb_root *root,
while (match != NULL && match->start < end) {
struct rb_node *node;
- if (match->start == start && match->end == end)
+ if ((match_type == MEMTYPE_EXACT_MATCH) &&
+ (match->start == start) && (match->end == end))
+ return match;
+
+ if ((match_type == MEMTYPE_END_MATCH) &&
+ (match->start < start) && (match->end == end))
return match;
node = rb_next(&match->rb);
@@ -117,7 +127,7 @@ static struct memtype *memtype_rb_exact_match(struct rb_root *root,
match = NULL;
}
- return NULL; /* Returns NULL if there is no exact match */
+ return NULL; /* Returns NULL if there is no match */
}
static int memtype_rb_check_conflict(struct rb_root *root,
@@ -210,12 +220,36 @@ struct memtype *rbt_memtype_erase(u64 start, u64 end)
{
struct memtype *data;
- data = memtype_rb_exact_match(&memtype_rbroot, start, end);
- if (!data)
- goto out;
+ /*
+ * Since the memtype_rbroot tree allows overlapping ranges,
+ * rbt_memtype_erase() checks with EXACT_MATCH first, i.e. free
+ * a whole node for the munmap case. If no such entry is found,
+ * it then checks with END_MATCH, i.e. shrink the size of a node
+ * from the end for the mremap case.
+ */
+ data = memtype_rb_match(&memtype_rbroot, start, end,
+ MEMTYPE_EXACT_MATCH);
+ if (!data) {
+ data = memtype_rb_match(&memtype_rbroot, start, end,
+ MEMTYPE_END_MATCH);
+ if (!data)
+ return ERR_PTR(-EINVAL);
+ }
+
+ if (data->start == start) {
+ /* munmap: erase this node */
+ rb_erase_augmented(&data->rb, &memtype_rbroot,
+ &memtype_rb_augment_cb);
+ } else {
+ /* mremap: update the end value of this node */
+ rb_erase_augmented(&data->rb, &memtype_rbroot,
+ &memtype_rb_augment_cb);
+ data->end = start;
+ data->subtree_max_end = data->end;
+ memtype_rb_insert(&memtype_rbroot, data);
+ return NULL;
+ }
- rb_erase_augmented(&data->rb, &memtype_rbroot, &memtype_rb_augment_cb);
-out:
return data;
}
--
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