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Message-Id: <20120323154502.8072a755.akpm@linux-foundation.org>
Date: Fri, 23 Mar 2012 15:45:02 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jan Kara <jack@...e.cz>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org,
Al Viro <viro@...IV.linux.org.uk>,
Christoph Hellwig <hch@...radead.org>, dchinner@...hat.com,
sandeen@...hat.com, Kamal Mostafa <kamal@...onical.com>
Subject: Re: [PATCH 01/19] mm: Make default vm_ops provide ->page_mkwrite
handler
On Mon, 5 Mar 2012 17:00:59 +0100
Jan Kara <jack@...e.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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