diff for duplicates of <20160810161345.GA67522@black.fi.intel.com> diff --git a/a/1.txt b/N1/1.txt index b5c41c5..6f47d92 100644 --- a/a/1.txt +++ b/N1/1.txt @@ -13,3 +13,46 @@ On Wed, Aug 10, 2016 at 07:33:38AM -0700, Laura Abbott wrote: > [ 1013.736091] kernel BUG at mm/rmap.c:1288! The patch below should do the trick. + +>From 8026e3a2cecb7cdd3a63ebc266fb359ef7ec965b Mon Sep 17 00:00:00 2001 +From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> +Date: Wed, 10 Aug 2016 18:51:54 +0300 +Subject: [PATCH] mm, rmap: fix false positive VM_BUG() in page_add_file_rmap() + +PageTransCompound() doesn't distinguish THP from from any other type of +compound pages. This can lead to false-positive VM_BUG_ON() in +page_add_file_rmap() if called on compound page from a driver[1]. + +I think we can exclude such cases by checking if the page belong to a +mapping. + +The VM_BUG_ON_PAGE() is downgraded to VM_WARN_ON_ONCE(). This path +should not cause any harm to non-THP page, but good to know if we step +on anything else. + +[1] http://lkml.kernel.org/r/c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com + +Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> +Reported-by: Laura Abbott <labbott@redhat.com> +--- + mm/rmap.c | 5 +++-- + 1 file changed, 3 insertions(+), 2 deletions(-) + +diff --git a/mm/rmap.c b/mm/rmap.c +index eee844997bd8..f071d6f7a986 100644 +--- a/mm/rmap.c ++++ b/mm/rmap.c +@@ -1286,8 +1286,9 @@ void page_add_file_rmap(struct page *page, bool compound) + else + __inc_node_page_state(page, NR_FILE_PMDMAPPED); + } else { +- if (PageTransCompound(page)) { +- VM_BUG_ON_PAGE(!PageLocked(page), page); ++ if (PageTransCompound(page) && page_mapping(page)) { ++ VM_WARN_ON_ONCE(!PageLocked(page)); ++ + SetPageDoubleMap(compound_head(page)); + if (PageMlocked(page)) + clear_page_mlock(compound_head(page)); +-- + Kirill A. Shutemov diff --git a/a/content_digest b/N1/content_digest index 9c3b6ff..12bb848 100644 --- a/a/content_digest +++ b/N1/content_digest @@ -22,6 +22,49 @@ "> [ 1013.736044] ------------[ cut here ]------------\n" "> [ 1013.736091] kernel BUG at mm/rmap.c:1288!\n" "\n" - The patch below should do the trick. + "The patch below should do the trick.\n" + "\n" + ">From 8026e3a2cecb7cdd3a63ebc266fb359ef7ec965b Mon Sep 17 00:00:00 2001\n" + "From: \"Kirill A. Shutemov\" <kirill.shutemov@linux.intel.com>\n" + "Date: Wed, 10 Aug 2016 18:51:54 +0300\n" + "Subject: [PATCH] mm, rmap: fix false positive VM_BUG() in page_add_file_rmap()\n" + "\n" + "PageTransCompound() doesn't distinguish THP from from any other type of\n" + "compound pages. This can lead to false-positive VM_BUG_ON() in\n" + "page_add_file_rmap() if called on compound page from a driver[1].\n" + "\n" + "I think we can exclude such cases by checking if the page belong to a\n" + "mapping.\n" + "\n" + "The VM_BUG_ON_PAGE() is downgraded to VM_WARN_ON_ONCE(). This path\n" + "should not cause any harm to non-THP page, but good to know if we step\n" + "on anything else.\n" + "\n" + "[1] http://lkml.kernel.org/r/c711e067-0bff-a6cb-3c37-04dfe77d2db1@redhat.com\n" + "\n" + "Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>\n" + "Reported-by: Laura Abbott <labbott@redhat.com>\n" + "---\n" + " mm/rmap.c | 5 +++--\n" + " 1 file changed, 3 insertions(+), 2 deletions(-)\n" + "\n" + "diff --git a/mm/rmap.c b/mm/rmap.c\n" + "index eee844997bd8..f071d6f7a986 100644\n" + "--- a/mm/rmap.c\n" + "+++ b/mm/rmap.c\n" + "@@ -1286,8 +1286,9 @@ void page_add_file_rmap(struct page *page, bool compound)\n" + " \t\telse\n" + " \t\t\t__inc_node_page_state(page, NR_FILE_PMDMAPPED);\n" + " \t} else {\n" + "-\t\tif (PageTransCompound(page)) {\n" + "-\t\t\tVM_BUG_ON_PAGE(!PageLocked(page), page);\n" + "+\t\tif (PageTransCompound(page) && page_mapping(page)) {\n" + "+\t\t\tVM_WARN_ON_ONCE(!PageLocked(page));\n" + "+\n" + " \t\t\tSetPageDoubleMap(compound_head(page));\n" + " \t\t\tif (PageMlocked(page))\n" + " \t\t\t\tclear_page_mlock(compound_head(page));\n" + "-- \n" + Kirill A. Shutemov -fce2b5d5d49d5a70231b15805abda53b9df2f5ea4e2ce02f7fe953d7307a9e9c +33af7827ff8c20f064baf3f2bd1fd300561be286354429fd77e5a0dc7274544e
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