Commit 1e61b8c6 authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba

btrfs: don't unconditionally call folio_start_writeback in subpage

In the normal case we check if a page is under writeback and skip it
before we attempt to begin writeback.

The exception is subpage metadata writes, where we know we don't have an
eb under writeback and we're doing it one eb at a time.  Since
b5612c36 ("mm: return void from folio_start_writeback() and related
functions") we now will BUG_ON() if we call folio_start_writeback()
on a folio that's already under writeback.  Previously
folio_start_writeback() would bail if writeback was already started.

Fix this in the subpage code by checking if we have writeback set and
skipping it if we do.  This fixes the panic we were seeing on subpage.
Reviewed-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarAnand Jain <anand.jain@oracle.com>
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 2018ef1d
......@@ -475,6 +475,7 @@ void btrfs_subpage_set_writeback(const struct btrfs_fs_info *fs_info,
spin_lock_irqsave(&subpage->lock, flags);
bitmap_set(subpage->bitmaps, start_bit, len >> fs_info->sectorsize_bits);
if (!folio_test_writeback(folio))
folio_start_writeback(folio);
spin_unlock_irqrestore(&subpage->lock, flags);
}
......
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