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Date: Thu, 24 Aug 2017 09:16:24 +0200 From: Jan Kara <jack@...e.cz> To: Christoph Hellwig <hch@...radead.org> Cc: Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org, linux-nvdimm@...ts.01.org, Andy Lutomirski <luto@...nel.org>, linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org, Ross Zwisler <ross.zwisler@...ux.intel.com>, Dan Williams <dan.j.williams@...el.com>, Boaz Harrosh <boazh@...app.com> Subject: Re: [PATCH 10/13] mm: Wire up MAP_SYNC On Wed 23-08-17 11:43:49, Christoph Hellwig wrote: > On Thu, Aug 17, 2017 at 06:08:12PM +0200, Jan Kara wrote: > > Pretty crude for now... > > > > Signed-off-by: Jan Kara <jack@...e.cz> > > --- > > fs/ext4/file.c | 2 ++ > > include/linux/mm.h | 1 + > > include/linux/mman.h | 3 ++- > > include/uapi/asm-generic/mman.h | 1 + > > mm/mmap.c | 5 +++++ > > 5 files changed, 11 insertions(+), 1 deletion(-) > > > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c > > index f84bb29e941e..850037e140d7 100644 > > --- a/fs/ext4/file.c > > +++ b/fs/ext4/file.c > > @@ -340,6 +340,8 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma) > > vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE; > > } else { > > vma->vm_ops = &ext4_file_vm_ops; > > + if (vma->vm_flags & VM_SYNC) > > + return -EOPNOTSUPP; > > } > > So each mmap instance would need to reject the flag explicitly? > > Or do I misunderstand this VM_SYNC flag? Yes, if this should be cleaned up, then each mmap instance not supporting it would need to reject it. However Dan has in his version of mmap() syscall a mask of supported flags so when I switch to that, it would be just opt-in. Or I could just reject VM_SYNC for any !IS_DAX inode so then only ext2 & xfs would need to reject it... But the biggest problem with this patch is that we need to settle on a safe way of adding new mmap flag. Honza -- Jan Kara <jack@...e.com> SUSE Labs, CR
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