On Sun, Apr 15, 2018 at 07:49:16AM +0200, Greg KH wrote:
> On Sun, Apr 15, 2018 at 12:36:02AM +0530, Souptick Joarder wrote:
> > Use new return type vm_fault_t for fault handler
> > in struct vm_operations_struct.
>
> Why?
commit 1c8f422059ae5da07db7406ab916203f9417e396
Author: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Date: Thu Apr 5 16:25:23 2018 -0700
mm: change return type to vm_fault_t
The plan for these patches is to introduce the typedef, initially just
as documentation ("These functions should return a VM_FAULT_ status").
We'll trickle the patches to individual drivers/filesystems in through
the maintainers, as far as possible. Then we'll change the typedef to
an unsigned int and break the compilation of any unconverted
drivers/filesystems.
vmf_insert_page(), vmf_insert_mixed() and vmf_insert_pfn() are three
newly added functions. The various drivers/filesystems where return
value of fault(), huge_fault(), page_mkwrite() and pfn_mkwrite() get
converted, will need them. These functions will return correct
VM_FAULT_ code based on err value.
We've had bugs before where drivers returned -EFOO. And we have this
silly inefficiency where vm_insert_xxx() return an errno which (afaict)
every driver then converts into a VM_FAULT code. In many cases drivers
failed to return correct VM_FAULT code value despite of vm_insert_xxx()
fails. We have indentified and clean up all those existing bugs and
silly inefficiencies in driver/filesystems by adding these three new
inline wrappers. As mentioned above, we will trickle those patches to
individual drivers/filesystems in through maintainers after these three
wrapper functions are merged.
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