[PATCH 2/2] mm: Fix devm_memremap_pages() collision handling

[Jan H . Schönherr]

If devm_memremap_pages() detects a collision while adding entries
to the radix-tree, we call pgmap_radix_release(). Unfortunately,
the function removes *all* entries for the range -- including the
entries that caused the collision in the first place.

Modify pgmap_radix_release() to take an additional argument to
indicate where to stop, so that only newly added entries are removed
from the tree.

Fixes: 9476df7d80df ("mm: introduce find_dev_pagemap()")
Signed-off-by: Jan H. Schönherr <jscho...@amazon.de>
---
 kernel/memremap.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 4712ce6..2b136d4 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -248,13 +248,16 @@ int device_private_entry_fault(struct vm_area_struct *vma,
 EXPORT_SYMBOL(device_private_entry_fault);
 #endif /* CONFIG_DEVICE_PRIVATE */
 
-static void pgmap_radix_release(struct resource *res)
+static void pgmap_radix_release(struct resource *res, unsigned long end_pgoff)
 {
        unsigned long pgoff, order;
 
        mutex_lock(&pgmap_lock);
-       foreach_order_pgoff(res, order, pgoff)
+       foreach_order_pgoff(res, order, pgoff) {
+               if (pgoff >= end_pgoff)
+                       break;
                radix_tree_delete(&pgmap_radix, PHYS_PFN(res->start) + pgoff);
+       }
        mutex_unlock(&pgmap_lock);
 
        synchronize_rcu();
@@ -309,7 +312,7 @@ static void devm_memremap_pages_release(struct device *dev, 
void *data)
        mem_hotplug_done();
 
        untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
-       pgmap_radix_release(res);
+       pgmap_radix_release(res, -1);
        dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
                        "%s: failed to free all reserved pages\n", __func__);
 }
@@ -459,7 +462,7 @@ void *devm_memremap_pages(struct device *dev, struct 
resource *res,
        untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
  err_pfn_remap:
  err_radix:
-       pgmap_radix_release(res);
+       pgmap_radix_release(res, pgoff);
        devres_free(page_map);
        return ERR_PTR(error);
 }
-- 
2.9.3.1.gcba166c.dirty