Starting with patch 2cb1e08985, gfs2 started using the new function
filemap_splice_read rather than the old (and subsequently deleted)
function generic_file_splice_read.

filemap_splice_read works by taking references to a number of folios in
the page cache and splicing those folios into a pipe.  The folios are
then read from the pipe and the folio references are dropped.  This can
take an arbitrary amount of time.  We cannot allow that in gfs2 because
those folio references will pin the inode glock to the node and prevent
it from being demoted, which can lead to cluster-wide deadlocks.

Instead, use copy_splice_read.

(In addition, the old generic_file_splice_read called into ->read_iter,
which called gfs2_file_read_iter, which took the inode glock during the
operation.  The new filemap_splice_read interface does not take the
inode glock anymore.  This is fixable, but it still wouldn't prevent
cluster-wide deadlocks.)

Fixes: 2cb1e08985e3 ("splice: Use filemap_splice_read() instead of generic_file_splice_read()")
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Function gfs2_trans_add_meta() checks for the SDF_FROZEN flag to make
sure that no buffers are added to a transaction while the filesystem is
frozen.  With the recent freeze/thaw rework, the SDF_FROZEN flag is
cleared after thaw_super() is called, which is sufficient for
serializing freeze/thaw.

However, other filesystem operations started after thaw_super() may now
be calling gfs2_trans_add_meta() before the SDF_FROZEN flag is cleared,
which will trigger the SDF_FROZEN check in gfs2_trans_add_meta().  Fix
that by checking the s_writers.frozen state instead.

In addition, make sure not to call gfs2_assert_withdraw() with the
sd_log_lock spin lock held.  Check for a withdrawn filesystem before
checking for a frozen filesystem, and don't pin/add buffers to the
current transaction in case of a failure in either case.

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

Pull gfs2 updates from Andreas Gruenbacher:

 - Move the freeze/thaw logic from glock callback context to process /
   worker thread context to prevent deadlocks

 - Fix a quota reference couting bug in do_qc()

 - Carry on deallocating inodes even when gfs2_rindex_update() fails

 - Retry filesystem-internal reads when they are interruped by a signal

 - Eliminate kmap_atomic() in favor of kmap_local_page() /
   memcpy_{from,to}_page()

 - Get rid of noop_direct_IO

 - And a few more minor fixes and cleanups

* tag 'gfs2-v6.4-rc5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2: (23 commits)
  gfs2: Add quota_change type
  gfs2: Use memcpy_{from,to}_page where appropriate
  gfs2: Convert remaining kmap_atomic calls to kmap_local_page
  gfs2: Replace deprecated kmap_atomic with kmap_local_page
  gfs: Get rid of unnucessary locking in inode_go_dump
  gfs2: gfs2_freeze_lock_shared cleanup
  gfs2: Replace sd_freeze_state with SDF_FROZEN flag
  gfs2: Rework freeze / thaw logic
  gfs2: Rename SDF_{FS_FROZEN => FREEZE_INITIATOR}
  gfs2: Reconfiguring frozen filesystem already rejected
  gfs2: Rename gfs2_freeze_lock{ => _shared }
  gfs2: Rename the {freeze,thaw}_super callbacks
  gfs2: Rename remaining "transaction" glock references
  gfs2: retry interrupted internal reads
  gfs2: Fix possible data races in gfs2_show_options()
  gfs2: Fix duplicate should_fault_in_pages() call
  gfs2: set FMODE_CAN_ODIRECT instead of a dummy direct_IO method
  gfs2: Don't remember delete unless it's successful
  gfs2: Update rl_unlinked before releasing rgrp lock
  gfs2: Fix gfs2_qa_get imbalance in gfs2_quota_hold
  ...

Function do_qc has two main uses: (1) to re-sync the local quota changes
(qd) to the master quotas, and (2) normal quota changes. In the case of
normal quota changes, the change can be positive or negative, as the
quota usage goes up and down.

Before this patch function do_qc was distinguishing one from another by
whether the resulting value is or isn't zero: In the case of a re-sync
(called do_sync) the quota value is moved from the temporary value to a
master value, so the amount is added to one and subtracted from the
other. The problem is that since the values can be positive or negative
we can occasionally run into situations where we are not doing a re-sync
but the quota change just happens to cancel out the previous value.

In the case of a re-sync extra references and locks are taken, and so
do_qc needs to release them. In the case of a normal quota change, no
extra references and locks are taken, so it must not try to release
them.

The problem is: if the quota change is not a re-sync but the value just
happens to cancel out the original quota change, the resulting zero
value fools do_qc into thinking this is a re-sync and therefore it must
release the extra references. This results in problems, mainly having to
do with slot reference numbers going smaller than zero.

This patch introduces new constants, QC_SYNC and QC_CHANGE so do_qc can
really tell the difference. For QC_SYNC calls it must release the extra
references acquired by gfs2_quota_unlock's call to qd_check_sync. For
QC_CHANGE calls it does not have extra references to put.

Note that this allows quota changes back to a value of zero, and so I
removed an assert warning related to that.

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

Replace kmap_local_page() + memcpy() + kunmap_local() sequences with
memcpy_{from,to}_page() where we are not doing anything else with the
mapped page.

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

Replace the remaining instances of kmap_atomic() ... kunmap_atomic()
with kmap_local_page() ... kunmap_local().

In gfs2_write_buf_to_page(), we can call flush_dcache_page() after
unmapping the page.

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

kmap_atomic() is deprecated in favor of kmap_local_{folio,page}().

Therefore, replace kmap_atomic() with kmap_local_page() in
gfs2_internal_read() and stuffed_readpage().

kmap_atomic() disables page-faults and preemption (the latter only for
!PREEMPT_RT kernels), However, the code within the mapping/un-mapping in
gfs2_internal_read() and stuffed_readpage() does not depend on the
above-mentioned side effects.

Therefore, a mere replacement of the old API with the new one is all that
is required (i.e., there is no need to explicitly add any calls to
pagefault_disable() and/or preempt_disable()).

Signed-off-by: Deepak R Varma <drv@mailo.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Commit 27a2660f1ef9 ("gfs2: Dump nrpages for inodes and their glocks")
added some locking around reading inode->i_data.nrpages.  That locking
doesn't do anything really, so get rid of it.

With that, the glock argument to ->go_dump() can be made const again as
well.

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

All the remaining users of gfs2_freeze_lock_shared() set freeze_gh to
&sdp->sd_freeze_gh and flags to 0, so remove those two parameters.

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

Replace sd_freeze_state with a new SDF_FROZEN flag.

There no longer is a need for indicating that a freeze is in progress
(SDF_STARTING_FREEZE); we are now protecting the critical sections with
the sd_freeze_mutex.

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