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    SubjectRe: [PATCH] 9p: add write-cache support to loose cache mode (take 3)
    On 2/16/07, Andrew Morton <akpm@linux-foundation.org> wrote:
    > On Fri, 16 Feb 2007 09:37:01 -0600 Eric Van Hensbergen <ericvh@gmail.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;
    > > + pgoff_t end_index;
    > > + 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 */
    > > + }
    > > +
    > > + buffer = kmap(page);
    > > + offset = ((loff_t) page->index << PAGE_CACHE_SHIFT);
    > > + page_cache_get(page);
    > > + retval = v9fs_write(filp, NULL, buffer, count, &offset);
    > > +
    > > kunmap(page);
    > > +
    > > + UnlockPage:
    > > unlock_page(page);
    > > + page_cache_release(page);
    > > +
    > > return retval;
    > > }
    >
    > The page_cache_get/release here aren't needed: lock_page suffices.
    >
    > Are you sure the page refcounting is right if the `goto UnlockPage'
    > happens?
    >
    > Can that goto actually happen??
    >

    It shouldn't, if it does we are probably in big trouble anyways. I'll
    pull it out. Thanks.

    -eric
    -
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