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mm: create the new vm_fault_t type
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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>
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@torvalds
Souptick Joarder authored and torvalds committed Mar 8, 2019
1 parent c2938ee commit 3d35390
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Showing 3 changed files with 73 additions and 48 deletions.
2 changes: 1 addition & 1 deletion arch/x86/mm/fault.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

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46 changes: 0 additions & 46 deletions include/linux/mm.h
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Expand Up @@ -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.
*/
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73 changes: 72 additions & 1 deletion include/linux/mm_types.h
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Expand Up @@ -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;
Expand Down Expand Up @@ -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]". */

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