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Message-Id: <20070213162625.0797d156.akpm@linux-foundation.org>
Date: Tue, 13 Feb 2007 16:26:25 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Eric Van Hensbergen <ericvh@...il.com>
Cc: linux-kernel@...r.kernel.org, v9fs-developer@...ts.sourceforge.net,
ericvh@...il.com
Subject: Re: [RESEND][PATCH] 9p: add write-cache support to loose cache mode
> On Tue, 13 Feb 2007 17:55:31 -0600 Eric Van Hensbergen <ericvh@...il.com> wrote:
> +static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
> +{
> + char *buffer = NULL;
> + struct address_space *mapping = page->mapping;
> + int retval = -EIO;
> + loff_t offset = 0;
> + loff_t pageoffset = 0;
> + unsigned long end_index;
Cosmetic detail: pgoff_t here.
> + int count = PAGE_CACHE_SIZE;
> + struct file *filp = v9fs_find_file(page);
> + struct inode *inode = mapping->host;
> +
> + dprintk(DEBUG_VFS, "page: %p\n", page);
> +
> + if ((!inode) || (!filp))
> + goto UnlockPage;
> +
> + end_index = inode->i_size >> PAGE_CACHE_SHIFT;
> +
> + /* complicated case at end of file */
> + if (page->index >= end_index) {
> + /* things got complicated... */
> + count = inode->i_size & (PAGE_CACHE_SIZE - 1);
> + if (page->index >= end_index + 1 || !count)
> + return 0; /* truncated - don't care */
> + }
> +
> + /* get buffer */
> + buffer = kmap(page) + pageoffset;
kmap_atomic() is faster and less deadlocky. But presumably v9fs_write()
prevents that.
> + offset = ((loff_t) page->index << PAGE_CACHE_SHIFT) + pageoffset;
> +
> + page_cache_get(page);
> +
> + retval = v9fs_write(filp, NULL, buffer, count, &offset);
> +
> + if (retval < 0) {
> + dprintk(DEBUG_ERROR, "error: %d\n", retval);
> + ClearPageUptodate(page);
> + goto UnmapPage;
> + }
I think you'll find that the ->writepage() caller handles all this. The
callers also set AS_EIO, which this code forgot.
> + if (retval < count) {
> + dprintk(DEBUG_ERROR, "Short write\n");
> + }
> +
> + if (offset > inode->i_size) {
> + inode->i_size = offset;
> + }
Can this happen??
If so, mark_inode_dirty() seems to be missing.
> + if (PageError(page))
> + ClearPageError(page);
Is this needed?
> + SetPageUptodate(page);
I'd expect that v9fs_writepage() is only ever called against uptodate pages?
> + retval = 0;
> +
> + UnmapPage:
> kunmap(page);
> + UnlockPage:
> unlock_page(page);
> + page_cache_release(page);
> +
> return retval;
> }
-
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