Re: [PATCH] jfs: clear PAGECACHE_TAG_DIRTY for no-write pages

Dave Kleikamp
2007-12-29T04:51:16Z

On Sat, 2007-12-29 at 10:21 +0800, Fengguang Wu wrote:
> On Fri, Dec 28, 2007 at 10:53:14AM -0600, Dave Kleikamp wrote:
>
>
> > ---
> >
> > diff -Nurp linux-2.6.24-rc6-git5/fs/jfs/jfs_metapage.c linux/fs/jfs/jfs_metapage.c
> > --- linux-2.6.24-rc6-git5/fs/jfs/jfs_metapage.c 2007-12-28 10:28:33.000000000 -0600
> > +++ linux/fs/jfs/jfs_metapage.c 2007-12-28 10:37:30.000000000 -0600
> > @@ -360,6 +360,7 @@ static int metapage_writepage(struct pag
> > struct metapage *mp;
> > int redirty = 0;
> > sector_t lblock;
> > + int nr_underway = 0;
> > sector_t pblock;
> > sector_t next_block = 0;
> > sector_t page_start;
> > @@ -371,6 +372,7 @@ static int metapage_writepage(struct pag
> > (PAGE_CACHE_SHIFT - inode->i_blkbits);
> > BUG_ON(!PageLocked(page));
> > BUG_ON(PageWriteback(page));
>
> This line should be moved below:
> > + set_page_writeback(page);

No. set_page_writeback() needs to be called before submit_bio() is
called.

I don't think there is any harm in calling set_page_writeback(),
redirty_page_for_writeback() and end_page_writeback() in the case where
there is no I/O to submit, and some dirty data cannot be written. It is
consistent with what happens in __block_write_full_page().

It's also possible that some part of the page was written, and another
part cannot be, causing the page to be redirtied.

> >
> > for (offset = 0; offset < PAGE_CACHE_SIZE; offset += PSIZE) {
> > mp = page_to_mp(page, offset);
> > @@ -413,11 +415,10 @@ static int metapage_writepage(struct pag
> > if (!bio->bi_size)
> > goto dump_bio;
> > submit_bio(WRITE, bio);
> > + nr_underway++;
> > bio = NULL;
> > - } else {
> > - set_page_writeback(page);
> > + } else
> > inc_io(page);
> > - }
> > xlen = (PAGE_CACHE_SIZE - offset) >> inode->i_blkbits;
> > pblock = metapage_get_blocks(inode, lblock, &xlen);
> > if (!pblock) {
> > @@ -449,12 +450,16 @@ static int metapage_writepage(struct pag
> > goto dump_bio;
> >
> > submit_bio(WRITE, bio);
> > + nr_underway++;
> > }
> > if (redirty)
> > redirty_page_for_writepage(wbc, page);
> + else
> + set_page_writeback(page);
> >
> > unlock_page(page);
> >
> > + if (nr_underway == 0)
> + if (nr_underway == 0 && redirty == 0)
>
> > + end_page_writeback(page);
> > +
> > return 0;
> > add_failed:
> > /* We should never reach here, since we're only adding one vec */
>
> Otherwise looks pretty good.
>
> Reviewed-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
>
--
David Kleikamp
IBM Linux Technology Center