[PATCH 6.1.y 6.6.y 0/3] mm/filemap: fix page cache corruption with large folios

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

This series fixes the page cache corruption issue reported by Christian
Theune [1]. The issue was reported affects kernels back to 5.19.
Current maintained effected branches includes 6.1 and 6.6 and the fix
was included in 6.10 already.

This series can be applied for both 6.1 and 6.6.

Patch 3/3 is the fixing patch. It was initially submitted and merge as
an optimization but found to have fixed the corruption by handling race
correctly.

Patch 1/3 and 2/3 is required for 3/3.

Patch 3/3 included some unit test code, making the LOC of the backport a
bit higher, but should be OK to be kept, since they are just test code.

Note there seems still some unresolved problem in Link [1] but that
should be a different issue, and the commits being backported have been
well tested, they fix the corruption issue just fine.

Link: https://lore.kernel.org/linux-mm/A5A976CB-DB57-4513-A700-656580488AB6@flyingcircus.io/ [1]

Kairui Song (3):
  mm/filemap: return early if failed to allocate memory for split
  lib/xarray: introduce a new helper xas_get_order
  mm/filemap: optimize filemap folio adding

 include/linux/xarray.h |  6 +++
 lib/test_xarray.c      | 93 ++++++++++++++++++++++++++++++++++++++++++
 lib/xarray.c           | 49 ++++++++++++++--------
 mm/filemap.c           | 50 ++++++++++++++++++-----
 4 files changed, 169 insertions(+), 29 deletions(-)

-- 
2.46.1