On Mon 02-06-08 15:22:22, Aneesh Kumar K.V wrote:
> Hi Jan,
>
>
> On Mon, Jun 02, 2008 at 11:31:06AM +0200, Jan Kara wrote:
> > Hi Aneesh,
> >
> > Thanks for the patch but I though we decided to do this a bit differently -
> > see below.
>
> Please feel free to merge the changes back to the lock inversion
> patches. I sent it as a separate the patches to make it easier for review.
OK, thanks. I'll look into this.
> > >
> > > + if (walk_page_buffers(NULL, page_bufs, 0,
> > > + len, NULL, ext4_bh_unmapped_or_delay)) {
> > > + printk(KERN_CRIT "%s called with unmapped or delay buffer\n",
> > > + __func__);
> > > + BUG();
> > > + }
> > > + /* FIXME!! do we need to call prepare_write for a mapped buffer */
> > This can go to ext4_journalled_writepage(). What is actually this FIXME
> > about? I'm not sure I get it...
> >
> I was wondering whether we need to call prepare_write in writepage ?. We
> are not allocating any new blocks in writepage with these changes.
Ah, I see. I'm only not sure whether we can rely on all buffers in the
page being uptodate... Otherwise I think block_prepare_write() is not
needed.
> > > ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE, ext4_get_block);
> > > if (ret != 0)
> > > goto out_unlock;
> > >
> > > - page_bufs = page_buffers(page);
> > > walk_page_buffers(handle, page_bufs, 0, PAGE_CACHE_SIZE, NULL,
> > > bget_one);
> > > /* As soon as we unlock the page, it can go away, but we have
> > > @@ -1671,14 +1713,13 @@ static int __ext4_journalled_writepage(struct page *page,
> > > static int ext4_journalled_writepage(struct page *page,
> > > struct writeback_control *wbc)
> > > {
> > > + BUG_ON(!page_has_buffers(page));
> > > +
> > > if (ext4_journal_current_handle())
> > > goto no_write;
> > >
> > > - if (!page_has_buffers(page) || PageChecked(page)) {
> > > - /*
> > > - * It's mmapped pagecache. Add buffers and journal it. There
> > > - * doesn't seem much point in redirtying the page here.
> > > - */
> > > + if (PageChecked(page)) {
> > > + /* dirty pages in data=journal mode */
> > > ClearPageChecked(page);
> > > return __ext4_journalled_writepage(page, wbc);
> > > } else {
> > > @@ -3520,6 +3561,96 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
> > > return err;
> > > }
> > >
> > > +static int __ext4_journalled_allocpage(struct page *page,
> > > + struct writeback_control *wbc)
> > > +{
> > > + int ret = 0, err;
> > > + handle_t *handle = NULL;
> > > + struct address_space *mapping = page->mapping;
> > > + struct inode *inode = mapping->host;
> > > + struct buffer_head *page_bufs;
> > > +
> > > + /* if alloc we are called after statring a journal */
> > > + handle = ext4_journal_current_handle();
> > > + BUG_ON(!handle);
> > > +
> > > + ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE, ext4_get_block);
> > > + if (ret != 0)
> > > + goto out_unlock;
> > > +
> > > + /* FIXME!! should we do a bget_one */
> > > + page_bufs = page_buffers(page);
> > > + ret = walk_page_buffers(handle, page_bufs, 0,
> > > + PAGE_CACHE_SIZE, NULL, do_journal_get_write_access);
> > > +
> I also have a FIXME here. I am not sure whether unlocking the page have
> some effect. Can you verify this ?
Well, you unlock the page only after you're completely done with it as
far as I read the code. So that is correct. You only need to get references
to buffers when you need to access them after you unlock the page.
> > > + err = walk_page_buffers(handle, page_bufs, 0,
> > > + PAGE_CACHE_SIZE, NULL, write_end_fn);
> > > + if (ret == 0)
> > > + ret = err;
> > > + EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
> > > +
> > > +out_unlock:
> > > + unlock_page(page);
> > > + return ret;
> > > +}
> > > +
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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