btrfs: fix deadlock with extent-same and readpage
->readpage() does page_lock() before extent_lock(), we do the opposite in extent-same. We want to reverse the order in btrfs_extent_same() but it's not quite straightforward since the page locks are taken inside btrfs_cmp_data(). So I split btrfs_cmp_data() into 3 parts with a small context structure that is passed between them. The first, btrfs_cmp_data_prepare() gathers up the pages needed (taking page lock as required) and puts them on our context structure. At this point, we are safe to lock the extent range. Afterwards, we use btrfs_cmp_data() to do the data compare as usual and btrfs_cmp_data_free() to clean up our context. Signed-off-by:Mark Fasheh <mfasheh@suse.de> Reviewed-by:
David Sterba <dsterba@suse.cz> Signed-off-by:
Chris Mason <clm@fb.com>
parent
207910dd
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