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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>