More new code for 5.13:
- Rename the log timestamp struct.
- Remove broken transaction counter debugging that wasn't working
  correctly on very old filesystems.
- Various fixes to make pre-lazysbcount filesystems work properly again.
- Fix a free space accounting problem where we neglected to consider
  free space btree blocks that track metadata reservation space when
  deciding whether or not to allow caller to reserve space for
  a metadata update.
- Fix incorrect pagecache clearing behavior during FUNSHARE ops.
- Don't allow log writes if the data device is readonly.
xfs: don't allow log writes if the data device is readonly

While running generic/050 with an external log, I observed this warning
in dmesg:

Trying to write to read-only block-device sda4 (partno 4)
WARNING: CPU: 2 PID: 215677 at block/blk-core.c:704 submit_bio_checks+0x256/0x510
Call Trace:
 submit_bio_noacct+0x2c/0x430
 _xfs_buf_ioapply+0x283/0x3c0 [xfs]
 __xfs_buf_submit+0x6a/0x210 [xfs]
 xfs_buf_delwri_submit_buffers+0xf8/0x270 [xfs]
 xfsaild+0x2db/0xc50 [xfs]
 kthread+0x14b/0x170

I think this happened because we tried to cover the log after a readonly
mount, and the AIL tried to write the primary superblock to the data
device.  The test marks the data device readonly, but it doesn't do the
same to the external log device.  Therefore, XFS thinks that the log is
writable, even though AIL writes whine to dmesg because the data device
is read only.

Fix this by amending xfs_log_writable to prevent writes when the AIL
can't possible write anything into the filesystem.

Note: As for the external log or the rt devices being readonly--
xfs_blkdev_get will complain about that if we aren't doing a norecovery
mount.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
1 file changed