mm: create the new vm_fault_t type

Page fault handlers are supposed to return VM_FAULT codes, but some
drivers/file systems mistakenly return error numbers.  Now that all
drivers/file systems have been converted to use the vm_fault_t return
type, change the type definition to no longer be compatible with 'int'.
By making it an unsigned int, the function prototype becomes
incompatible with a function which returns int.  Sparse will detect any
attempts to return a value which is not a VM_FAULT code.

VM_FAULT_SET_HINDEX and VM_FAULT_GET_HINDEX values are changed to avoid
conflict with other VM_FAULT codes.

[jrdr.linux@gmail.com: fix warnings]
Link: http://lkml.kernel.org/r/20190109183742.GA24326@jordon-HP-15-Notebook-PC
Link: http://lkml.kernel.org/r/20190108183041.GA12137@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9d5c75f..667f1da 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1031,7 +1031,7 @@ bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
 
 static void
 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
-         unsigned int fault)
+         vm_fault_t fault)
 {
        struct task_struct *tsk = current;
 

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 20ec56f..5801ee8 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1322,52 +1322,6 @@ static inline void clear_page_pfmemalloc(struct page *page)
        page->index = 0;
 }
 
-/*
- * Different kinds of faults, as returned by handle_mm_fault().
- * Used to decide whether a process gets delivered SIGBUS or
- * just gets major/minor fault counters bumped up.
- */
-
-#define VM_FAULT_OOM   0x0001
-#define VM_FAULT_SIGBUS        0x0002
-#define VM_FAULT_MAJOR 0x0004
-#define VM_FAULT_WRITE 0x0008  /* Special case for get_user_pages */
-#define VM_FAULT_HWPOISON 0x0010       /* Hit poisoned small page */
-#define VM_FAULT_HWPOISON_LARGE 0x0020  /* Hit poisoned large page. Index encoded in upper bits */
-#define VM_FAULT_SIGSEGV 0x0040
-
-#define VM_FAULT_NOPAGE        0x0100  /* ->fault installed the pte, not return page */
-#define VM_FAULT_LOCKED        0x0200  /* ->fault locked the returned page */
-#define VM_FAULT_RETRY 0x0400  /* ->fault blocked, must retry */
-#define VM_FAULT_FALLBACK 0x0800       /* huge page fault failed, fall back to small */
-#define VM_FAULT_DONE_COW   0x1000     /* ->fault has fully handled COW */
-#define VM_FAULT_NEEDDSYNC  0x2000     /* ->fault did not modify page tables
-                                        * and needs fsync() to complete (for
-                                        * synchronous page faults in DAX) */
-
-#define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | \
-                        VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE | \
-                        VM_FAULT_FALLBACK)
-
-#define VM_FAULT_RESULT_TRACE \
-       { VM_FAULT_OOM,                 "OOM" }, \
-       { VM_FAULT_SIGBUS,              "SIGBUS" }, \
-       { VM_FAULT_MAJOR,               "MAJOR" }, \
-       { VM_FAULT_WRITE,               "WRITE" }, \
-       { VM_FAULT_HWPOISON,            "HWPOISON" }, \
-       { VM_FAULT_HWPOISON_LARGE,      "HWPOISON_LARGE" }, \
-       { VM_FAULT_SIGSEGV,             "SIGSEGV" }, \
-       { VM_FAULT_NOPAGE,              "NOPAGE" }, \
-       { VM_FAULT_LOCKED,              "LOCKED" }, \
-       { VM_FAULT_RETRY,               "RETRY" }, \
-       { VM_FAULT_FALLBACK,            "FALLBACK" }, \
-       { VM_FAULT_DONE_COW,            "DONE_COW" }, \
-       { VM_FAULT_NEEDDSYNC,           "NEEDDSYNC" }
-
-/* Encode hstate index for a hwpoisoned large page */
-#define VM_FAULT_SET_HINDEX(x) ((x) << 12)
-#define VM_FAULT_GET_HINDEX(x) (((x) >> 12) & 0xf)
-
 /*
  * Can be called by the pagefault handler when it gets a VM_FAULT_OOM.
  */

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index ab9b484..86e7a7a 100644 (file)
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -22,7 +22,6 @@
 #endif
 #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))
 
-typedef int vm_fault_t;
 
 struct address_space;
 struct mem_cgroup;
@@ -621,6 +620,78 @@ static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
 
 struct vm_fault;
 
+/**
+ * typedef vm_fault_t - Return type for page fault handlers.
+ *
+ * Page fault handlers return a bitmask of %VM_FAULT values.
+ */
+typedef __bitwise unsigned int vm_fault_t;
+
+/**
+ * enum vm_fault_reason - Page fault handlers return a bitmask of
+ * these values to tell the core VM what happened when handling the
+ * fault. Used to decide whether a process gets delivered SIGBUS or
+ * just gets major/minor fault counters bumped up.
+ *
+ * @VM_FAULT_OOM:              Out Of Memory
+ * @VM_FAULT_SIGBUS:           Bad access
+ * @VM_FAULT_MAJOR:            Page read from storage
+ * @VM_FAULT_WRITE:            Special case for get_user_pages
+ * @VM_FAULT_HWPOISON:         Hit poisoned small page
+ * @VM_FAULT_HWPOISON_LARGE:   Hit poisoned large page. Index encoded
+ *                             in upper bits
+ * @VM_FAULT_SIGSEGV:          segmentation fault
+ * @VM_FAULT_NOPAGE:           ->fault installed the pte, not return page
+ * @VM_FAULT_LOCKED:           ->fault locked the returned page
+ * @VM_FAULT_RETRY:            ->fault blocked, must retry
+ * @VM_FAULT_FALLBACK:         huge page fault failed, fall back to small
+ * @VM_FAULT_DONE_COW:         ->fault has fully handled COW
+ * @VM_FAULT_NEEDDSYNC:                ->fault did not modify page tables and needs
+ *                             fsync() to complete (for synchronous page faults
+ *                             in DAX)
+ * @VM_FAULT_HINDEX_MASK:      mask HINDEX value
+ *
+ */
+enum vm_fault_reason {
+       VM_FAULT_OOM            = (__force vm_fault_t)0x000001,
+       VM_FAULT_SIGBUS         = (__force vm_fault_t)0x000002,
+       VM_FAULT_MAJOR          = (__force vm_fault_t)0x000004,
+       VM_FAULT_WRITE          = (__force vm_fault_t)0x000008,
+       VM_FAULT_HWPOISON       = (__force vm_fault_t)0x000010,
+       VM_FAULT_HWPOISON_LARGE = (__force vm_fault_t)0x000020,
+       VM_FAULT_SIGSEGV        = (__force vm_fault_t)0x000040,
+       VM_FAULT_NOPAGE         = (__force vm_fault_t)0x000100,
+       VM_FAULT_LOCKED         = (__force vm_fault_t)0x000200,
+       VM_FAULT_RETRY          = (__force vm_fault_t)0x000400,
+       VM_FAULT_FALLBACK       = (__force vm_fault_t)0x000800,
+       VM_FAULT_DONE_COW       = (__force vm_fault_t)0x001000,
+       VM_FAULT_NEEDDSYNC      = (__force vm_fault_t)0x002000,
+       VM_FAULT_HINDEX_MASK    = (__force vm_fault_t)0x0f0000,
+};
+
+/* Encode hstate index for a hwpoisoned large page */
+#define VM_FAULT_SET_HINDEX(x) ((__force vm_fault_t)((x) << 16))
+#define VM_FAULT_GET_HINDEX(x) (((x) >> 16) & 0xf)
+
+#define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS |       \
+                       VM_FAULT_SIGSEGV | VM_FAULT_HWPOISON |  \
+                       VM_FAULT_HWPOISON_LARGE | VM_FAULT_FALLBACK)
+
+#define VM_FAULT_RESULT_TRACE \
+       { VM_FAULT_OOM,                 "OOM" },        \
+       { VM_FAULT_SIGBUS,              "SIGBUS" },     \
+       { VM_FAULT_MAJOR,               "MAJOR" },      \
+       { VM_FAULT_WRITE,               "WRITE" },      \
+       { VM_FAULT_HWPOISON,            "HWPOISON" },   \
+       { VM_FAULT_HWPOISON_LARGE,      "HWPOISON_LARGE" },     \
+       { VM_FAULT_SIGSEGV,             "SIGSEGV" },    \
+       { VM_FAULT_NOPAGE,              "NOPAGE" },     \
+       { VM_FAULT_LOCKED,              "LOCKED" },     \
+       { VM_FAULT_RETRY,               "RETRY" },      \
+       { VM_FAULT_FALLBACK,            "FALLBACK" },   \
+       { VM_FAULT_DONE_COW,            "DONE_COW" },   \
+       { VM_FAULT_NEEDDSYNC,           "NEEDDSYNC" }
+
 struct vm_special_mapping {
        const char *name;       /* The name, e.g. "[vdso]". */