On 5/29/2021 4:36 PM, Ming Lin wrote:
On 5/29/2021 1:15 PM, Hugh Dickins wrote:
I believe the correct behaviour would be to unmap the nofault page
then, allowing the proper page to be faulted in after. That is
certainly doable (the old mm/filemap_xip.c used to do so), but might
get into some awkward race territory, with filesystem dependence
(reminiscent of hole punch, in reverse). shmem could operate that
way, and be the better for it: but I wouldn't want to add that,
without also cleaning away all the shmem_recalc_inode() stuff.
OK, I borrowed code from filemap_xip.c and implemented this behavior.
Simon,
Before I send out the patches for review, would you mind have a quick test?
https://github.com/minggr/linux, branch shmem_no_sigbus
In Wayland compositors, you only need to pass in MAP_NOSIGBUS in mmap().
For example,
//fd should be received from Wayland compositors client
#define MAP_NOSIGBUS 0x200000
addr = mmap(NULL, size, PROT_READ, MAP_SHARED|MAP_NOSIGBUS, fd, offset)
Thanks,
Ming
