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From:   Souptick Joarder <jrdr.linux@gmail.com>
Date:   Mon, 7 Jan 2019 11:47:12 +0530
Message-ID: <CAFqt6zYY=xfqvVxRi1spbMNzvoM_CYNxbm6d7_79a5bBHxUzuA@mail.gmail.com>
Subject: Re: [PATCH v3] mm: Create the new vm_fault_t type
To:     rppt@linux.ibm.com, Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Matthew Wilcox <willy@infradead.org>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        vbabka@suse.cz, riel@redhat.com, Linux-MM <linux-mm@kvack.org>,
        linux-kernel@vger.kernel.org
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On Fri, Dec 14, 2018 at 10:35 AM Souptick Joarder <jrdr.linux@gmail.com> wrote:
>
> Hi Andrew,
>
> On Sat, Nov 24, 2018 at 10:16 AM Souptick Joarder <jrdr.linux@gmail.com> wrote:
> >
> > On Thu, Nov 15, 2018 at 7:17 AM Mike Rapoport <rppt@linux.ibm.com> wrote:
> > >
> > > On Tue, Nov 06, 2018 at 05:36:42PM +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>
> > >
> > > For the docs part
> > > Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
> > >
> > > > ---
> > > > v2: Updated the change log and corrected the document part.
> > > >     name added to the enum that kernel-doc able to parse it.
> > > >
> > > > v3: Corrected the documentation.
> >
> > If no further comment, can we get this patch in queue for 4.21 ?
>
> Do I need to make any further improvement for this patch ?

If no further comment, can we get this patch in queue for 5.0-rcX ?

> >
> > > >
> > > >  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..cb25016 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_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]". */
> > > >
> > > > --
> > > > 1.9.1
> > > >
> > >
> > > --
> > > Sincerely yours,
> > > Mike.
> > >