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_MATCH 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.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: stsp@list.ru
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/1450832064-10093-3-git-send-email-toshi.kani@hpe.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 1aca073..031782e 100644 (file)
--- 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 (file)
--- 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;
 }