On Mon, Apr 16, 2018 at 05:02:00PM -0600, Ross Zwisler wrote:
> I'm not sure what you mean by "vm_fault_t will become a distinct type"? Do
> you mean you'll make it into an enum, i.e.:
>
> enum vm_fault_t {
> VM_FAULT_OOM = 0x0001,
> VM_FAULT_SIGBUS = 0x0002,
> VM_FAULT_MAJOR = 0x0004,
> VM_FAULT_WRITE = 0x0008,
> VM_FAULT_HWPOISON = 0x0010,
> VM_FAULT_HWPOISON_LARGE = 0x0020,
> VM_FAULT_NOPAGE = 0x0100,
> VM_FAULT_LOCKED = 0x0200,
> VM_FAULT_RETRY = 0x0400,
> VM_FAULT_FALLBACK = 0x0800,
> VM_FAULT_DONE_COW = 0x1000,
> VM_FAULT_NEEDDSYNC = 0x2000,
> };
My current tree has this in it:
+/*
+ * Different kinds of faults, as returned from fault handlers.
+ * Used to decide whether a process gets delivered SIGBUS or
+ * just gets major/minor fault counters bumped up.
+ */
+typedef __bitwise unsigned int vm_fault_t;
+enum {
+ VM_FAULT_OOM = (__force vm_fault_t)0x000001, /* Out Of
Memory */
+ VM_FAULT_SIGBUS = (__force vm_fault_t)0x000002, /* Bad access */
+ VM_FAULT_MAJOR = (__force vm_fault_t)0x000004, /* Page read
from storage */
+ VM_FAULT_WRITE = (__force vm_fault_t)0x000008, /* Special case
for get_user_pages */
+ VM_FAULT_HWPOISON = (__force vm_fault_t)0x000010, /* Hit poisoned
small page */
+ VM_FAULT_HWPOISON_LARGE = (__force vm_fault_t)0x000020, /* Hit poisoned
large page. Index encoded in upper bits */
+ VM_FAULT_SIGSEGV = (__force vm_fault_t)0x000040,
+ VM_FAULT_NOPAGE = (__force vm_fault_t)0x000100, /* ->fault
installed the pte, not return page */
+ VM_FAULT_LOCKED = (__force vm_fault_t)0x000200, /* ->fault
locked the returned page */
+ VM_FAULT_RETRY = (__force vm_fault_t)0x000400, /* ->fault
blocked, must retry */
+ VM_FAULT_FALLBACK = (__force vm_fault_t)0x000800, /* huge page
fault failed, fall back to small */
+ VM_FAULT_DONE_COW = (__force vm_fault_t)0x001000, /* ->fault has
fully handled COW */
+ VM_FAULT_NEEDDSYNC = (__force vm_fault_t)0x002000, /* ->fault did
not modify page tables
+ * and needs fsync() to complete (for
+ * synchronous page faults in DAX) */
+ VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000,
+};
However, I'm hoping to get a better syntax into sparse ;-)
> If so, I think that would be great for readability. Right now I look up the
> definition of vm_fault_t and see it's typedef'd to an int, and that doesn't
> give me as much info as the above enum would.
>
> If this is the plan, I don't understand why you need to make all the site
> conversions first?
Changing it from a signed to an unsigned int causes GCC to warn about
an assignment from an incompatible type -- int foo(void) is incompatible
with unsigned int foo(void).
> Sure, the code looks correct. You can add:
> Reviewed-by: Ross Zwisler <[email protected]>
Thanks, Ross.
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