btrfs: fix hang when run_delalloc_range() failed
[BUG]
When running subpage preparation patches on x86, btrfs/125 will hang
forever with one ordered extent never finished.
[CAUSE]
The test case btrfs/125 itself will always fail as the fix is never merged.
When the test fails at balance, btrfs needs to cleanup the ordered
extent in btrfs_cleanup_ordered_extents() for data reloc inode.
The problem is in the sequence how we cleanup the page Order bit.
Currently it works like:
btrfs_cleanup_ordered_extents()
|- find_get_page();
|- btrfs_page_clear_ordered(page);
| Now the page doesn't have Ordered bit anymore.
| !!! This also includes the first (locked) page !!!
|
|- offset += PAGE_SIZE
| This is to skip the first page
|- __endio_write_update_ordered()
|- btrfs_mark_ordered_io_finished(NULL)
Except the first page, all ordered extents are finished.
Then the locked page is cleaned up in __extent_writepage():
__extent_writepage()
|- If (PageError(page))
|- end_extent_writepage()
|- btrfs_mark_ordered_io_finished(page)
|- if (btrfs_test_page_ordered(page))
|- !!! The page gets skipped !!!
The ordered extent is not decreased as the page doesn't
have ordered bit anymore.
This leaves the ordered extent with bytes_left == sectorsize, thus never
finish.
[FIX]
The fix is to ensure we never clear page Ordered bit without running the
ordered extent accounting.
Here we choose to skip the locked page in
btrfs_cleanup_ordered_extents() so that later end_extent_writepage() can
properly finish the ordered extent.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 412abf9..2eedcf6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -166,10 +166,31 @@ static inline void btrfs_cleanup_ordered_extents(struct btrfs_inode *inode,
struct page *page;
while (index <= end_index) {
+ /*
+ * For locked page, we will call end_extent_writepage() on it
+ * in run_delalloc_range() for the error handling. That
+ * end_extent_writepage() function will call
+ * btrfs_mark_ordered_io_finished() to clear page Ordered and
+ * run the ordered extent accounting.
+ *
+ * Here we can't just clear the Ordered bit, or
+ * btrfs_mark_ordered_io_finished() would skip the accounting
+ * for the page range, and the ordered extent will never finish.
+ */
+ if (index == (page_offset(locked_page) >> PAGE_SHIFT)) {
+ index++;
+ continue;
+ }
page = find_get_page(inode->vfs_inode.i_mapping, index);
index++;
if (!page)
continue;
+
+ /*
+ * Here we just clear all Ordered bits for every page in the
+ * range, then __endio_write_update_ordered() will handle
+ * the ordered extent accounting for the range.
+ */
ClearPageOrdered(page);
put_page(page);
}