This fixes as case in "btrfs: refactor alloc_extent_buffer() to
allocate-then-attach method".
We have been seeing panics in the CI for the subpage stuff recently, it
happens on btrfs/187 but could potentially happen anywhere.
In the subpage case, if we race with somebody else inserting the same
extent buffer, the error case will end up calling
detach_extent_buffer_page() on the page twice.
This is done first in the bit
for (int i = 0; i < attached; i++)
detach_extent_buffer_page(eb, eb->pages[i];
and then again in btrfs_release_extent_buffer().
This works fine for !subpage because we're the only person who ever has
ourselves on the private, and so when we do the initial
detach_extent_buffer_page() we know we've completely removed it.
However for subpage we could be using this page private elsewhere, so
this results in a double put on the subpage, which can result in an
early freeing.
The fix here is to clear eb->pages[i] for everything we detach. Then
anything still attached to the eb is freed in
btrfs_release_extent_buffer().
Because of this change we must update
btrfs_release_extent_buffer_pages() to not use num_extent_folios,
because it assumes eb->folio[0] is set properly. Since this is only
interested in freeing any pages we have on the extent buffer we can
simply use INLINE_EXTENT_BUFFER_PAGES.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
4a565c8069