[PATCH v4 00/10] ceph: convert writeback path to folios

Convert ceph's writeback path to work on folios. These conversions
eliminate the last callers of three mm compatibility APIs:
wait_on_page_writeback(), thp_size(), and thp_order(). Their removals
will be sent separately once the conversions land, per Ceph maintainer
request.

This also fixes a couple pre-existing issues discovered by Sashiko
along the way.

Some page <-> folio boundaries are deliberately left in place where
ceph borders on some gnarlier page-based APIs:

- libceph's OSD data plane is page-array based, so ceph_writeback_ctl's
  pages[] and osd_data->pages[] remain struct page arrays. Folios are
  converted at the array/libceph boundary.

- fscrypt's bounce page API remains page-based for some functions
  (fscrypt_encrypt_pagecache_blocks(), fscrypt_finalize_bounce_page()).
  Possibly-bounce array entries are unwrapped to their pagecache folios
  via fscrypt_pagecache_folio().

This series is based on the ceph-client testing branch [1].

[1] https://github.com/ceph/ceph-client/tree/testing

Signed-off-by: Tal Zussman <[email protected]>
---
Changes in v4:
- Rebase onto the current ceph-client testing branch
- Drop the two mm patches removing wait_on_page_writeback(), thp_size(),
  and thp_order(), per Alex
- Patch 2: wait for the pending fscache write before bumping the
  writeback congestion count and allocating the OSD request, per
  Sashiko
- Link to v3: https://lore.kernel.org/r/20260810-remove-wait-on-page-writeback-v3-0-dd7531704f26@columbia.edu

Changes in v3:
- Add patches 1 and 2, fixing a couple pre-existing bugs found by Sashiko
- Patch 7 (was patch 5): Rework the ceph_submit_write() error path
  conversion on top of patch 1
- Patch 10 (was patch 8): Remove the BUG_ON(), per Sashiko and Matthew
- Link to v2: https://lore.kernel.org/r/20260804-remove-wait-on-page-writeback-v2-0-81f0ab065284@columbia.edu

Changes in v2:
- Propagate tags (thanks David and Matthew!)
- Rebase onto ceph-client.git testing
- Rename the series to "ceph: convert writeback path to folios"
- Patch 1: Drop the folio_test_private() check in
  ceph_folio_snap_context(), per Matthew and Zi.
- Patch 4: Introduce ceph_fscrypt folio helpers and use them in
  get_writepages_data_length(), per Matthew.
- Patches 5-10: new
- Link to v1: https://lore.kernel.org/r/20260802-remove-wait-on-page-writeback-v1-0-6c35d6b3ad36@columbia.edu

---
Tal Zussman (10):
      ceph: fix error handling when the OSD client is stopping in ceph_submit_write()
      ceph: wait for pending fscache write in write_folio_nounlock()
      ceph: add ceph_folio_snap_context()
      ceph: convert ceph_wait_until_current_writes_complete() to folios
      ceph: convert get_writepages_data_length() to folios
      ceph: convert ceph_submit_write() to folios
      ceph: remove page remnants from write_folio_nounlock()
      ceph: convert page cleanup loop in writepages_finish() to folios
      ceph: remove ceph_fscrypt_pagecache_page() and ceph_fscrypt_page_offset()
      ceph: rename ceph_check_page_before_write() to ceph_check_folio_before_write()

 fs/ceph/addr.c   | 156 ++++++++++++++++++++++++++++++-------------------------
 fs/ceph/crypto.h |  12 ++---
 2 files changed, 91 insertions(+), 77 deletions(-)
---
base-commit: fce4f3da41f1145cfa400002ce3a66e4a89a1902
change-id: 20260802-remove-wait-on-page-writeback-8e0cb766d4c7

Best regards,
-- 
Tal Zussman <[email protected]>