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mm/mremap_pages: Fix static key devmap_managed_key updates

PATCH Applied Ralph Campbell 2 participants 2 messages Oct 23, 2020 – Oct 24, 2020

Subsystems (3)
Memory management libnvdimm: non-volatile memory device Memory hot(un)plug
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Ralph Campbell

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PATCH 1/1 mm/mremap_pages: Fix static key devmap_managed_key updates

commit 6f42193fd86e ("memremap: don't use a separate devm action for devmap_managed_enable_get") changed the static key updates such that we now call devmap_managed_enable_put() without doing the equivalent devmap_managed_enable_get().

devmap_managed_enable_get() is only called for MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_FS_DAX, But memunmap_pages() get called for other pgmap types too. This results in the below warning when switching between system-ram and devdax mode for devdax namespace.

jump label: negative count!

 WARNING: CPU: 52 PID: 1335 at kernel/jump_label.c:235 static_key_slow_try_dec+0x88/0xa0
 Modules linked in:
 ....

NIP [c000000000433318] static_key_slow_try_dec+0x88/0xa0 LR [c000000000433314] static_key_slow_try_dec+0x84/0xa0

 Call Trace:
 [c000000025c1f660] [c000000000433314] static_key_slow_try_dec+0x84/0xa0
 [c000000025c1f6d0] [c000000000433664] __static_key_slow_dec_cpuslocked+0x34/0xd0
 [c000000025c1f700] [c0000000004337a4] static_key_slow_dec+0x54/0xf0
 [c000000025c1f770] [c00000000059c49c] memunmap_pages+0x36c/0x500
 [c000000025c1f820] [c000000000d91d10] devm_action_release+0x30/0x50
 [c000000025c1f840] [c000000000d92e34] release_nodes+0x2f4/0x3e0
 [c000000025c1f8f0] [c000000000d8b15c] device_release_driver_internal+0x17c/0x280
 [c000000025c1f930] [c000000000d883a4] bus_remove_device+0x124/0x210
 [c000000025c1f9b0] [c000000000d80ef4] device_del+0x1d4/0x530
 [c000000025c1fa70] [c000000000e341e8] unregister_dev_dax+0x48/0xe0
 [c000000025c1fae0] [c000000000d91d10] devm_action_release+0x30/0x50
 [c000000025c1fb00] [c000000000d92e34] release_nodes+0x2f4/0x3e0
 [c000000025c1fbb0] [c000000000d8b15c] device_release_driver_internal+0x17c/0x280
 [c000000025c1fbf0] [c000000000d87000] unbind_store+0x130/0x170
 [c000000025c1fc30] [c000000000d862a0] drv_attr_store+0x40/0x60
 [c000000025c1fc50] [c0000000006d316c] sysfs_kf_write+0x6c/0xb0
 [c000000025c1fc90] [c0000000006d2328] kernfs_fop_write+0x118/0x280
 [c000000025c1fce0] [c0000000005a79f8] vfs_write+0xe8/0x2a0
 [c000000025c1fd30] [c0000000005a7d94] ksys_write+0x84/0x140
 [c000000025c1fd80] [c00000000003a430] system_call_exception+0x120/0x270
 [c000000025c1fe20] [c00000000000c540] system_call_common+0xf0/0x27c
Cc Christoph Hellwig <[email protected]>
Cc Dan Williams <[email protected]>
Cc [email protected]
Cc Jason Gunthorpe <[email protected]>
Signed-off-by Ralph Campbell <[email protected]>
Reported-by Aneesh Kumar K.V <[email protected]>
Reviewed-by Aneesh Kumar K.V <[email protected]>
Reviewed-by Ira Weiny <[email protected]>
Tested-by Sachin Sant <[email protected]>

---

Andrew, I guess this is for the merge window since it fixes a top-of-tree problem.

 mm/memremap.c | 39 ++++++++++++++++-----------------------
 1 file changed, 16 insertions(+), 23 deletions(-)
mm/memremap.c +16 -23
index 73a206d0f645..16b2fb482da1 100644
@@ -41,28 +41,24 @@ EXPORT_SYMBOL_GPL(memremap_compat_align);
 DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
 EXPORT_SYMBOL(devmap_managed_key);
 
-static void devmap_managed_enable_put(void)
+static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
 {
-	static_branch_dec(&devmap_managed_key);
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+	    pgmap->type == MEMORY_DEVICE_FS_DAX)
+		static_branch_dec(&devmap_managed_key);
 }
 
-static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
+static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
 {
-	if (pgmap->type == MEMORY_DEVICE_PRIVATE &&
-	    (!pgmap->ops || !pgmap->ops->page_free)) {
-		WARN(1, "Missing page_free method\n");
-		return -EINVAL;
-	}
-
-	static_branch_inc(&devmap_managed_key);
-	return 0;
+	if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+	    pgmap->type == MEMORY_DEVICE_FS_DAX)
+		static_branch_inc(&devmap_managed_key);
 }
 #else
-static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
+static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
 {
-	return -EINVAL;
 }
-static void devmap_managed_enable_put(void)
+static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
 {
 }
 #endif /* CONFIG_DEV_PAGEMAP_OPS */

@@ -169,7 +165,7 @@ void memunmap_pages(struct dev_pagemap *pgmap)
 		pageunmap_range(pgmap, i);
 
 	WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n");
-	devmap_managed_enable_put();
+	devmap_managed_enable_put(pgmap);
 }
 EXPORT_SYMBOL_GPL(memunmap_pages);
 

@@ -307,7 +303,6 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
 		.pgprot = PAGE_KERNEL,
 	};
 	const int nr_range = pgmap->nr_range;
-	bool need_devmap_managed = true;
 	int error, i;
 
 	if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))

@@ -323,6 +318,10 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
 			WARN(1, "Missing migrate_to_ram method\n");
 			return ERR_PTR(-EINVAL);
 		}
+		if (!pgmap->ops->page_free) {
+			WARN(1, "Missing page_free method\n");
+			return ERR_PTR(-EINVAL);
+		}
 		if (!pgmap->owner) {
 			WARN(1, "Missing owner\n");
 			return ERR_PTR(-EINVAL);

@@ -336,11 +335,9 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
 		}
 		break;
 	case MEMORY_DEVICE_GENERIC:
-		need_devmap_managed = false;
 		break;
 	case MEMORY_DEVICE_PCI_P2PDMA:
 		params.pgprot = pgprot_noncached(params.pgprot);
-		need_devmap_managed = false;
 		break;
 	default:
 		WARN(1, "Invalid pgmap type %d\n", pgmap->type);

@@ -364,11 +361,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
 		}
 	}
 
-	if (need_devmap_managed) {
-		error = devmap_managed_enable_get(pgmap);
-		if (error)
-			return ERR_PTR(error);
-	}
+	devmap_managed_enable_get(pgmap);
 
 	/*
 	 * Clear the pgmap nr_range as it will be incremented for each
Signature · 4 lines
2.20.1
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