[PATCH v2] mm: Create the new vm_fault_t type

[PATCH v2] mm: Create the new vm_fault_t type

[Souptick Joarder]

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.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
---
v2: Updated the change log and corrected the document part.
    name added to the enum that kernel-doc able to parse it.

 include/linux/mm.h       | 46 ------------------------------
 include/linux/mm_types.h | 73 +++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 72 insertions(+), 47 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index fcf9cc9..511a3ce 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1267,52 +1267,6 @@ static inline void clear_page_pfmemalloc(struct page *page)
 }
 
 /*
- * 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.
  */
 extern void pagefault_out_of_memory(void);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5ed8f62..beee607 100644
--- 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;
@@ -609,6 +608,78 @@ 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 code
+ *
+ * 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)
+ */
+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]". */
 
-- 
1.9.1

Re: [PATCH v2] mm: Create the new vm_fault_t type

[Mike Rapoport]

On Tue, Nov 06, 2018 at 01:19:34PM +0530, Souptick Joarder wrote:
> 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.
> 
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> ---
> v2: Updated the change log and corrected the document part.
>     name added to the enum that kernel-doc able to parse it.
> 
>  include/linux/mm.h       | 46 ------------------------------
>  include/linux/mm_types.h | 73 +++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 72 insertions(+), 47 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index fcf9cc9..511a3ce 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1267,52 +1267,6 @@ static inline void clear_page_pfmemalloc(struct page *page)
>  }
>  
>  /*
> - * 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.
>   */
>  extern void pagefault_out_of_memory(void);
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 5ed8f62..beee607 100644
> --- 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;
> @@ -609,6 +608,78 @@ 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 code

It should be 'enum vm_fault_reason' here.
A more elaborate brief description would also be nice.

> + *
> + * 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)
> + */
> +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]". */
>  
> -- 
> 1.9.1
> 

-- 
Sincerely yours,
Mike.

Re: [PATCH v2] mm: Create the new vm_fault_t type

[Souptick Joarder]

On Tue, Nov 6, 2018 at 1:56 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
>
> On Tue, Nov 06, 2018 at 01:19:34PM +0530, Souptick Joarder wrote:
> > 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.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> > ---
> > v2: Updated the change log and corrected the document part.
> >     name added to the enum that kernel-doc able to parse it.
> >
> >  include/linux/mm.h       | 46 ------------------------------
> >  include/linux/mm_types.h | 73 +++++++++++++++++++++++++++++++++++++++++++++++-
> >  2 files changed, 72 insertions(+), 47 deletions(-)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index fcf9cc9..511a3ce 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -1267,52 +1267,6 @@ static inline void clear_page_pfmemalloc(struct page *page)
> >  }
> >
> >  /*
> > - * 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.
> >   */
> >  extern void pagefault_out_of_memory(void);
> > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> > index 5ed8f62..beee607 100644
> > --- 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;
> > @@ -609,6 +608,78 @@ 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 code
>
> It should be 'enum vm_fault_reason' here.

Sorry, missed it.

> A more elaborate brief description would also be nice.

This much description is not sufficient to explain the enum ?
>
> > + *
> > + * 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)
> > + */
> > +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]". */
> >
> > --
> > 1.9.1
> >
>
> --
> Sincerely yours,
> Mike.
>

Re: [PATCH v2] mm: Create the new vm_fault_t type

[Mike Rapoport]

On Tue, Nov 06, 2018 at 02:04:54PM +0530, Souptick Joarder wrote:
> On Tue, Nov 6, 2018 at 1:56 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
> >
> > On Tue, Nov 06, 2018 at 01:19:34PM +0530, Souptick Joarder wrote:
> > > 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.
> > >
> > > Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> > > ---
> > > v2: Updated the change log and corrected the document part.
> > >     name added to the enum that kernel-doc able to parse it.
> > >
> > >  include/linux/mm.h       | 46 ------------------------------
> > >  include/linux/mm_types.h | 73 +++++++++++++++++++++++++++++++++++++++++++++++-
> > >  2 files changed, 72 insertions(+), 47 deletions(-)
> > >
> > > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > > index fcf9cc9..511a3ce 100644
> > > --- a/include/linux/mm.h
> > > +++ b/include/linux/mm.h
> > > @@ -1267,52 +1267,6 @@ static inline void clear_page_pfmemalloc(struct page *page)
> > >  }
> > >
> > >  /*
> > > - * 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.
> > >   */
> > >  extern void pagefault_out_of_memory(void);
> > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> > > index 5ed8f62..beee607 100644
> > > --- 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;
> > > @@ -609,6 +608,78 @@ 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 code
> >
> > It should be 'enum vm_fault_reason' here.
> 
> Sorry, missed it.
> 
> > A more elaborate brief description would also be nice.
>
> This much description is not sufficient to explain the enum ?
> >

The description below is fine, but kernel-doc will use "VM_FAULT code" as
the "short description" and the explanation will be used as "long
description".

So either replace "VM_FAULT code" with something like "page fault handler
return codes" or put the long explanation next to 'enum vm_fault_reason':

/**
 * enum vm_fault_reason - page fault handlers return a bitmask of these
 * values ...
 * ...
 */

Please take a look at "Structure, union, and enumeration documentation" in
Documentation/doc-guide/kernel-doc.rst [1].

[1] https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#structure-union-and-enumeration-documentation

> > > + *
> > > + * 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)
> > > + */
> > > +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]". */
> > >
> > > --
> > > 1.9.1
> > >
> >
> > --
> > Sincerely yours,
> > Mike.
> >
> 

-- 
Sincerely yours,
Mike.

Re: [PATCH v2] mm: Create the new vm_fault_t type

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1545 bytes --]

Hi Souptick,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.20-rc1 next-20181106]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Souptick-Joarder/mm-Create-the-new-vm_fault_t-type/20181106-171908
config: i386-randconfig-h1-11061829 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

>> drivers//dma-buf/udmabuf.c:34:2: warning: initialization from incompatible pointer type
     .fault = udmabuf_vm_fault,
     ^
   drivers//dma-buf/udmabuf.c:34:2: warning: (near initialization for 'udmabuf_vm_ops.fault')

vim +34 drivers//dma-buf/udmabuf.c

fbb0de79 Gerd Hoffmann 2018-08-27  32  
fbb0de79 Gerd Hoffmann 2018-08-27  33  static const struct vm_operations_struct udmabuf_vm_ops = {
fbb0de79 Gerd Hoffmann 2018-08-27 @34  	.fault = udmabuf_vm_fault,
fbb0de79 Gerd Hoffmann 2018-08-27  35  };
fbb0de79 Gerd Hoffmann 2018-08-27  36  

:::::: The code at line 34 was first introduced by commit
:::::: fbb0de795078190a9834b3409e4b009cfb18a6d4 Add udmabuf misc device

:::::: TO: Gerd Hoffmann <kraxel@redhat.com>
:::::: CC: Gerd Hoffmann <kraxel@redhat.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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