splice: Disable vmsplice on nommu.
PATCH 1/1 splice: Disable vmsplice on nommu.
The vmsplice rework in -mm breaks nommu:
fs/built-in.o: In function `splice_setup_vma':fs/splice.c:1272: undefined reference to may_expand_vm' fs/splice.c:1272: undefined reference to protection_map' fs/splice.c:1272: undefined reference to insert_vm_struct' fs/splice.c:1272: undefined reference to vm_stat_account'
This is going to be non-trivial to wire up properly on nommu, and it's debateable whether there's even any point in trying. For now, disable vmsplice if CONFIG_MMU=n and wire it up as a cond syscall for the platforms that support both.
--
fs/splice.c | 2 ++ kernel/sys_ni.c | 1 + 2 files changed, 3 insertions(+)
fs/splice.c +2 -0
@@ -1180,6 +1180,7 @@return -EINVAL ; } +#ifdef CONFIG_MMU /* * Undo vmsplice_to_user map. Basically just lookup the vmas and * detach/unmap/remove them.
@@ -1686,6 +1687,7 @@return error; } +#endif /* CONFIG_MMU */ asmlinkage long sys_splice(int fd_in, loff_t __user *off_in, int fd_out, loff_t __user *off_out,
kernel/sys_ni.c +1 -0
@@ -139,6 +139,7 @@cond_syscall (sys_madvise);cond_syscall (sys_mremap);cond_syscall (sys_remap_file_pages); +cond_syscall (sys_vmsplice);cond_syscall (compat_sys_move_pages);cond_syscall (compat_sys_migrate_pages);
Quoted 8 lines · Paul Mundt
The vmsplice rework in -mm breaks nommu:
fs/built-in.o: In function `splice_setup_vma':fs/splice.c:1272: undefined reference tomay_expand_vm' fs/splice.c:1272: undefined reference toprotection_map'fs/splice.c:1272: undefined reference toinsert_vm_struct' fs/splice.c:1272: undefined reference tovm_stat_account'
Quoted 4 lines
This is going to be non-trivial to wire up properly on nommu, and it's debateable whether there's even any point in trying. For now, disable vmsplice if
CONFIG_MMU=nand wire it up as a cond syscall for the platforms that support both.
It's a bit of a sledge hammer... Since get_user_pages() appears to work on nummu, we can just disable the vmsplice-to-userspace bits and leave the (working) vmsplice-from-userspace in place.
I'm reworking this code anyway in the block branches, so I'll update and take CONFIG_MMU into consideration.
Signature · 1 line
Jens Axboe
Quoted 3 lines · Jens Axboe
It's a bit of a sledge hammer... Since
get_user_pages()appears to work on nummu, we can just disable the vmsplice-to-userspace bits and leave the (working) vmsplice-from-userspace in place.
That sounds about right. I don't think you can do the latter without an MMU, but I may be wrong about what it does.
David
Quoted 8 lines · David Howells
Quoted 3 lines · Jens Axboe
It's a bit of a sledge hammer... Since
get_user_pages()appears to work on nummu, we can just disable the vmsplice-to-userspace bits and leave the (working) vmsplice-from-userspace in place.That sounds about right. I don't think you can do the latter without an MMU, but I may be wrong about what it does.
You mean the former? The latter is vmsplice() filling a pipe with user pages, using get_user_pages() to set them up. And that looks like it should work on nommu.
The former is vmsplice() using mmap like functionality to map pages into a user vma.
Just making sure we agree :-)
Signature · 1 line
Jens Axboe
Quoted 7 lines · Jens Axboe
Quoted 6 lines
Quoted 3 lines
It's a bit of a sledge hammer... Since
get_user_pages()appears to work on nummu, we can just disable the vmsplice-to-userspace bits and leave the (working) vmsplice-from-userspace in place.That sounds about right. I don't think you can do the latter without an MMU, but I may be wrong about what it does.
Quoted 6 lines
You mean the former? The latter is
vmsplice()filling a pipe with user pages, usingget_user_pages()to set them up. And that looks like it should work on nommu.The former is
vmsplice()using mmap like functionality to map pages into a user vma.
Sorry, yes. The former.
David