gfs2: use a folio inside gfs2_jdata_writepage()

gfs2: use a folio inside gfs2_jdata_writepage()

Patch series "gfs2/buffer folio changes for 6.5", v3.

This kind of started off as a gfs2 patch series, then became entwined with
buffer heads once I realised that gfs2 was the only remaining caller of
__block_write_full_page().  For those not in the gfs2 world, the big point
of this series is that block_write_full_page() should now handle large
folios correctly.

This patch (of 14):

Replace a few implicit calls to compound_head() with one explicit one.

Link: https://lkml.kernel.org/r/20230612210141.730128-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20230612210141.730128-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Bob Peterson <rpeterso@redhat.com>
Reviewed-by: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>