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Subject[08/25] ext4: Use tag dirty lookup during mpage_da_submit_io
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

commit af6f029d3836eb7264cd3fbb13a6baf0e5fdb5ea upstream.

This enables us to drop the range_cont writeback mode
use from ext4_da_writepages.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Jayson R. King <dev@jaysonking.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/ext4/inode.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1699,17 +1699,23 @@ static int mpage_da_submit_io(struct mpa

pagevec_init(&pvec, 0);
while (index <= end) {
- nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
+ /*
+ * We can use PAGECACHE_TAG_DIRTY lookup here because
+ * even though we have cleared the dirty flag on the page
+ * We still keep the page in the radix tree with tag
+ * PAGECACHE_TAG_DIRTY. See clear_page_dirty_for_io.
+ * The PAGECACHE_TAG_DIRTY is cleared in set_page_writeback
+ * which is called via the below writepage callback.
+ */
+ nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+ PAGECACHE_TAG_DIRTY,
+ min(end - index,
+ (pgoff_t)PAGEVEC_SIZE-1) + 1);
if (nr_pages == 0)
break;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];

- index = page->index;
- if (index > end)
- break;
- index++;
-
BUG_ON(!PageLocked(page));
BUG_ON(PageWriteback(page));

@@ -2442,7 +2448,6 @@ static int ext4_da_writepages(struct add
struct writeback_control *wbc)
{
handle_t *handle = NULL;
- loff_t range_start = 0;
struct mpage_da_data mpd;
struct inode *inode = mapping->host;
int needed_blocks, ret = 0, nr_to_writebump = 0;
@@ -2481,14 +2486,7 @@ static int ext4_da_writepages(struct add
wbc->nr_to_write = sbi->s_mb_stream_request;
}

- if (!wbc->range_cyclic)
- /*
- * If range_cyclic is not set force range_cont
- * and save the old writeback_index
- */
- wbc->range_cont = 1;

- range_start = wbc->range_start;
pages_skipped = wbc->pages_skipped;

mpd.wbc = wbc;
@@ -2559,9 +2557,8 @@ restart_loop:
wbc->nr_to_write = to_write;
}

- if (wbc->range_cont && (pages_skipped != wbc->pages_skipped)) {
+ if (!wbc->range_cyclic && (pages_skipped != wbc->pages_skipped)) {
/* We skipped pages in this loop */
- wbc->range_start = range_start;
wbc->nr_to_write = to_write +
wbc->pages_skipped - pages_skipped;
wbc->pages_skipped = pages_skipped;
@@ -2570,7 +2567,6 @@ restart_loop:

out_writepages:
wbc->nr_to_write = to_write - nr_to_writebump;
- wbc->range_start = range_start;
return ret;
}




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