Commit b2b0a5e97855 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
b2b0a5e97855 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 b2b0a5e978552e348f85ad9c7568b630a5ede659.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Acked-by: Christoph Hellwig <hch@lst.de>

Pull gfs2 updtaes from Andreas Gruenbacher:

 - Revert a change to delete_work_func() that has gone wrong in commit
   c412a97cf6c5 ("gfs2: Use TRY lock in gfs2_inode_lookup for UNLINKED
   inodes").

 - Avoid dequeuing GL_ASYNC glock holders twice by first checking if the
   holder is still queued.

 - gfs2: Always check the inode size of inline inodes when reading in
   inodes to prevent corrupt filesystem images from causing weid errors.

 - Properly handle a race between gfs2_create_inode() and
   gfs2_inode_lookup() that causes insert_inode_locked4() to return
   -EBUSY.

 - Fix and clean up the interaction between gfs2_create_inode() and
   gfs2_evict_inode() by completely handling the inode deallocation and
   destruction in gfs2_evict_inode().

 - Remove support for glock holder auto-demotion as we have no current
   plans of using this feature again.

 - And a few more minor cleanups and clarifications.

* tag 'gfs2-v6.1-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  gfs2: Remove support for glock holder auto-demotion (2)
  gfs2: Remove support for glock holder auto-demotion
  gfs2: Minor gfs2_try_evict cleanup
  gfs2: Partially revert gfs2_inode_lookup change
  gfs2: Add gfs2_inode_lookup comment
  gfs2: Uninline and improve glock_{set,clear}_object
  gfs2: Simply dequeue iopen glock in gfs2_evict_inode
  gfs2: Clean up after gfs2_create_inode rework
  gfs2: Avoid dequeuing GL_ASYNC glock holders twice
  gfs2: Make gfs2_glock_hold return its glock argument
  gfs2: Always check inode size of inline inodes
  gfs2: Cosmetic gfs2_dinode_{in,out} cleanup
  gfs2: Handle -EBUSY result of insert_inode_locked4
  gfs2: Fix and clean up create / evict interaction
  gfs2: Clean up initialization of "ip" in gfs2_create_inode
  gfs2: Get rid of ghs[] in gfs2_create_inode
  gfs2: Add extra error check in alloc_dinode

As a follow-up to the previous commit, move the recovery related code in
__gfs2_glock_dq() to gfs2_glock_dq() where it better fits.  No
functional change.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Remove the support for glock holder auto-demotion (commit dc732906c245
and folow-ups) as we are not planning to use this feature, and the
additional code therefore only adds unnecessary complexity.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

In gfs2_try_evict(), when an inode can't be evicted, we are grabbing a
temporary reference on the inode glock to poke that glock.  That should
be safe, but it's easier to just grab an inode reference as we already
do earlier in this function.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Commit c412a97cf6c5 changed delete_work_func() to always perform an
inode lookup when gfs2_try_evict() fails.  This doesn't make sense as a
gfs2_try_evict() failure indicates that the inode is likely still in
use.  Revert that change.

Fixes: c412a97cf6c5 ("gfs2: Use TRY lock in gfs2_inode_lookup for UNLINKED inodes")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Add comment on when and why gfs2_cancel_delete_work() needs to be
skipped in gfs2_inode_lookup().

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Those functions have reached a size at which having them inline isn't
useful anymore, so uninline them.  In addition, report the glock name on
assertion failures.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

With the previous change, to simplify things, we can always just dequeue
and uninitialize the iopen glock in gfs2_evict_inode() even if it isn't
queued anymore.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Since commit 3d36e57ff768 ("gfs2: gfs2_create_inode rework"),
gfs2_evict_inode() and gfs2_create_inode() / gfs2_inode_lookup() will
synchronize via the inode hash table and we can be certain that once a
new inode is inserted into the inode hash table(), gfs2_evict_inode()
has completely destroyed any previous versions.  We no longer need to
worry about overlapping inode object lifespans.  Update the code and
comments accordingly.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>