Commit b2b0a5e978 switched from generic_writepages() to
filemap_fdatawrite_wbc() in gfs2_ail1_start_one() on the path to
replacing ->writepage() with ->writepages() and eventually eliminating
the former. Function gfs2_ail1_start_one() is called from
gfs2_log_flush(), our main function for flushing the filesystem log.
Unfortunately, at least as implemented today, ->writepage() and
->writepages() are entirely different operations for journaled data
inodes: while the former creates and submits transactions covering the
data to be written, the latter flushes dirty buffers out to disk.
With gfs2_ail1_start_one() now calling ->writepages(), we end up
creating filesystem transactions while we are in the course of a log
flush, which immediately deadlocks on the sdp->sd_log_flush_lock
semaphore.
Work around that by going back to how things used to work before commit
b2b0a5e978 for now; figuring out a superior solution will take time we
don't have available right now. However ...
Since the removal of generic_writepages() is imminent, open-code it
here. We're already inside a blk_start_plug() ... blk_finish_plug()
section here, so skip that part of the original generic_writepages().
This reverts commit b2b0a5e978.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Acked-by: Christoph Hellwig <hch@lst.de>
95ecbd0f16