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SubjectRe: [PATCH 01/19] mm: Make default vm_ops provide ->page_mkwrite handler
On Mon,  5 Mar 2012 17:00:59 +0100
Jan Kara <jack@suse.cz> wrote:

> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1759,8 +1759,28 @@ page_not_uptodate:
> }
> EXPORT_SYMBOL(filemap_fault);
>
> +int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
> +{
> + struct page *page = vmf->page;
> + struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
> + int ret = VM_FAULT_LOCKED;
> +
> + file_update_time(vma->vm_file);
> + lock_page(page);
> + if ((page->mapping != inode->i_mapping) ||
> + (page_offset(page) > i_size_read(inode))) {

Would benefit from a comment explaining how the page can come to be
outside i_size, and why we fail in that case.

I don't think i_mutex is held here, so this test is rather meaningless
and racy anyway?

> + unlock_page(page);
> + ret = VM_FAULT_NOPAGE;
> + goto out;
> + }
> +out:
> + return ret;
> +}
> +EXPORT_SYMBOL(filemap_page_mkwrite);


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